As previously noted (in the thread about Paul's wife getting scared),
Mary and I had virtually stopped doing this kind of flying for fear of
harming our (very expensive) engine. A lively debate ensued as to
whether or not repeated high-to-low-to-high power applications would
wear out your engine any faster than would normal operations.

I eventually agreed that gradual power changes would not unduly harm
an air-cooled engine, and vowed that I would endeavor to practice this
most-important skill on our next flight. And we did.

We were on a flight back from Galesburg, IL when I started the
procedure, and very gradually began a power reduction whilst in cruise
flight at 3500 feet. I took a full minute to reduce the power to
idle, watching our (newly reinstalled) JPI EDM-700 engine analyzer for
signs of stress.

As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
off, flashing its dire warnings that EGTs had dropped beyond (and
faster) than recommended limits. (I can't remember what the threshold
is for that alarm -- it's preset.)

This despite my most careful power reduction, which (obviously) wasn't
slow enough.

Since the damage (so to speak) had already been done, I continued the
descent toward an Illinois corn field. With the harvest under way, I
had my choice of:

- Freshly harvested corn stubble, not plowed
- Freshly harvested crops, plowed dirt
- Unharvested corn or winter wheat

I opted for the corn stubble, as the stalks would hold the soil
together firmly and not present as much "flip force" to the landing
gear as the plowed or unharvested field. I took it down to 200 AGL
before applying power and heading home, satisfied that we would have
survived and giving the farmer a nice show.

For you aircraft owners who do this regularly, how slowly do you
retard the throttle to prevent shock cooling? (I know -- does shock
cooling really exist? For purposes of this discussion, I'll pretend
that it does.)

Given that the power reduction must be incredibly gradual, do you feel
that this exercise is realistic? There really is no chance to
simulate how you must "suddenly" find best glide speed (after your
engine has presumably just crapped out), since you're gradually
reducing your speed along with your power. Or do you put the plane
into a shallow dive as you reduce power, so as not to lose airspeed?

It's funny -- as renters we practiced this all the time. Now, after 9
years of ownership, we haven't practiced it in ages -- and didn't even
realize this lack until Shirl's comments in Paul's thread. Another
good thing about "belonging" to this newsgroup...

Thoughts?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

"Jay Honeck" wrote:
>
> As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
> off, flashing its dire warnings that EGTs had dropped beyond (and
> faster) than recommended limits. (I can't remember what the threshold
> is for that alarm -- it's preset.)

EGTs don't matter. Sure you don't mean CHTs? What temps. were you seeing?

IIRC, you can modify alarm limits. Check the manual.

> This despite my most careful power reduction, which (obviously) wasn't
> slow enough.

Does the bird have cowl flaps?


--
Dan
T-182T at BFM

"Jay Honeck" > wrote in message
ups.com...
> ...
> As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
> off, flashing its dire warnings that EGTs had dropped beyond (and
> faster) than recommended limits. (I can't remember what the threshold
> is for that alarm -- it's preset.)
> ...
> Jay Honeck

What happens when you do a normal pattern? Given your explaination, I would
assume that you get a shock cooling alarm everytime you do power reductions
as part of a normal landing. If not, use the same technique at altitude to
get into a power idle glide.

I don't have any engine analyzer. But, on a normal approach, I will reduce
throttle in two or three steps to get to 15" or 16". That supports my
minimum, flaps up, holding altitude speed. Then, with gear out and flaps
down, I'm descending on extended downwind, base and final, with the power
gradually coming off to flare. (I'm not describing this as the ideal
technique. I'm stating it so that others can say - "Are you crazy! That
technique is an engine killer.")

Engine out practice for me is very similar. From cruise, reduce throttle in
a couple of steps to 15". Maintain altitude. Then gradually pull off power
pitching over to maintain best glide. You're right, it's all very methodical
and does not present a sudden engine loss scenario. Maybe only do that once
or twice a year. For me, the engine out practice is all about picking the
spot and making it without power. Practicing that without instaneous loss of
engine power still has a lot of value.

Now, in my Lake, I've got other concerns. Several times a year and during
every annual insurance checkride, a sudden loss of engine power on takeoff
is a required demonstrated skill. With a top-mounted, pusher engine, in a
takeoff configuration, close to the ground, sudden engine loss and anything
but immediate response is deadly. The sudden loss of nose down thrust will
cause pitch up at a speed already close to stall with not much altitude to
recover. An immediate (and I mean immediate) push over is absolutely
critical. Critical enough that practice is necessary regardless of any harm
it might be doing to the engine.

So, for me, the engine-out on takeoff gets me practice responding quickly.
The more gradual throttle to idle and then a practice off-field approach
completes the scenario.

-------------------------------
Travis
Lake N3094P
PWK

Hey, if you're worried, go rent a plane that will glide in a similar
manner, and take a good instructor too.

john

Jay Honeck wrote:
> As previously noted (in the thread about Paul's wife getting scared),
> Mary and I had virtually stopped doing this kind of flying for fear of
> harming our (very expensive) engine. A lively debate ensued as to
> whether or not repeated high-to-low-to-high power applications would
> wear out your engine any faster than would normal operations.
>
> I eventually agreed that gradual power changes would not unduly harm
> an air-cooled engine, and vowed that I would endeavor to practice this
> most-important skill on our next flight. And we did.
>
> We were on a flight back from Galesburg, IL when I started the
> procedure, and very gradually began a power reduction whilst in cruise
> flight at 3500 feet. I took a full minute to reduce the power to
> idle, watching our (newly reinstalled) JPI EDM-700 engine analyzer for
> signs of stress.
>
> As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
> off, flashing its dire warnings that EGTs had dropped beyond (and
> faster) than recommended limits. (I can't remember what the threshold
> is for that alarm -- it's preset.)
>
> This despite my most careful power reduction, which (obviously) wasn't
> slow enough.
>
> Since the damage (so to speak) had already been done, I continued the
> descent toward an Illinois corn field. With the harvest under way, I
> had my choice of:
>
> - Freshly harvested corn stubble, not plowed
> - Freshly harvested crops, plowed dirt
> - Unharvested corn or winter wheat
>
> I opted for the corn stubble, as the stalks would hold the soil
> together firmly and not present as much "flip force" to the landing
> gear as the plowed or unharvested field. I took it down to 200 AGL
> before applying power and heading home, satisfied that we would have
> survived and giving the farmer a nice show.
>
> For you aircraft owners who do this regularly, how slowly do you
> retard the throttle to prevent shock cooling? (I know -- does shock
> cooling really exist? For purposes of this discussion, I'll pretend
> that it does.)
>
> Given that the power reduction must be incredibly gradual, do you feel
> that this exercise is realistic? There really is no chance to
> simulate how you must "suddenly" find best glide speed (after your
> engine has presumably just crapped out), since you're gradually
> reducing your speed along with your power. Or do you put the plane
> into a shallow dive as you reduce power, so as not to lose airspeed?
>
> It's funny -- as renters we practiced this all the time. Now, after 9
> years of ownership, we haven't practiced it in ages -- and didn't even
> realize this lack until Shirl's comments in Paul's thread. Another
> good thing about "belonging" to this newsgroup...
>
> Thoughts?
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"
>

Jay Honeck wrote:
> As previously noted (in the thread about Paul's wife getting scared),
> Mary and I had virtually stopped doing this kind of flying for fear of
> harming our (very expensive) engine. A lively debate ensued as to
> whether or not repeated high-to-low-to-high power applications would
> wear out your engine any faster than would normal operations.
>
> I eventually agreed that gradual power changes would not unduly harm
> an air-cooled engine, and vowed that I would endeavor to practice this
> most-important skill on our next flight. And we did.
>
> We were on a flight back from Galesburg, IL when I started the
> procedure, and very gradually began a power reduction whilst in cruise
> flight at 3500 feet. I took a full minute to reduce the power to
> idle, watching our (newly reinstalled) JPI EDM-700 engine analyzer for
> signs of stress.
>
> As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
> off, flashing its dire warnings that EGTs had dropped beyond (and
> faster) than recommended limits. (I can't remember what the threshold
> is for that alarm -- it's preset.)

When I practiced in my Skylane and also in the club Arrow, I retarded
the throttle smoothly in probably 2-3 seconds. I didn't worry about
shock cooling and never saw any signs of distress in either the O-470 or
the O-360.

The issue with shock cooling isn't the rate of cooling per se, but
rather stress induced by differential cooling. Most engines see far
higher temperature differentials during start-up than they do during
cooldown. Jay, have you timed your engine heat up rate? It would be
interesting to watch how fast your engine heats up from say a 50 degree
cold start and then compare that to the cool-down rate when you pull the
throttle for engine out practice. I'm assuming this would be fairly
trivial with your engine analyzer.

I'm not sure what your normal operating temps are, but I assume it is a
much larger delta between ambient and your normal operating temps than
between your normal operating temps and the temps you see during a glide
at idle. I also suspect that the rate of heat-up during take-off is at
least as high as the rate of cooling during an idle glide. However, it
would be very interesting to see the data if you are inclined to collect
it some day.

Matt

Travis Marlatte wrote:
> "Jay Honeck" > wrote in message
> ups.com...
>> ...
>> As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
>> off, flashing its dire warnings that EGTs had dropped beyond (and
>> faster) than recommended limits. (I can't remember what the threshold
>> is for that alarm -- it's preset.)
>> ...
>> Jay Honeck
>
> What happens when you do a normal pattern? Given your explaination, I would
> assume that you get a shock cooling alarm everytime you do power reductions
> as part of a normal landing. If not, use the same technique at altitude to
> get into a power idle glide.
>
> I don't have any engine analyzer. But, on a normal approach, I will reduce
> throttle in two or three steps to get to 15" or 16". That supports my
> minimum, flaps up, holding altitude speed. Then, with gear out and flaps
> down, I'm descending on extended downwind, base and final, with the power
> gradually coming off to flare. (I'm not describing this as the ideal
> technique. I'm stating it so that others can say - "Are you crazy! That
> technique is an engine killer.")

Have you killed any engines yet doing this?

Matt

On 2007-10-13 06:57:56 -0700, Jay Honeck > said:

> As previously noted (in the thread about Paul's wife getting scared),
> Mary and I had virtually stopped doing this kind of flying for fear of
> harming our (very expensive) engine. A lively debate ensued as to
> whether or not repeated high-to-low-to-high power applications would
> wear out your engine any faster than would normal operations.

Most flight schools practice engine out emergencies frequently, even on
high performance aircraft. The engines typically make it to TBO.

The things that seem to shorten engine life have little to do with
shock cooling. The biggest factor seems to be how much the engine is
used.

If the engine is flown in accordance with the manual, you should not
have any problems with shock cooling.



--
Waddling Eagle
World Famous Flight Instructor

> The issue with shock cooling isn't the rate of cooling per se, but
> rather stress induced by differential cooling.

Actually, I think it is the rate of cooling *and* the differential
cooling -- if it exists at all. Like you, I am skeptical -- but am I
willing to bet $25K on it? Nope.

Therefore, I fly as if it exists.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

> EGTs don't matter. Sure you don't mean CHTs? What temps. were you seeing?

Whoops. Right you are.

> IIRC, you can modify alarm limits. Check the manual.

Roger that.

> > This despite my most careful power reduction, which (obviously) wasn't
> > slow enough.
>
> Does the bird have cowl flaps?

Nope.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

On Oct 13, 8:57 am, Jay Honeck > wrote:
> As previously noted (in the thread about Paul's wife getting scared),
> Mary and I had virtually stopped doing this kind of flying for fear of
> harming our (very expensive) engine. A lively debate ensued as to
> whether or not repeated high-to-low-to-high power applications would
> wear out your engine any faster than would normal operations.
>
> I eventually agreed that gradual power changes would not unduly harm
> an air-cooled engine, and vowed that I would endeavor to practice this
> most-important skill on our next flight. And we did.
>
> We were on a flight back from Galesburg, IL when I started the
> procedure, and very gradually began a power reduction whilst in cruise
> flight at 3500 feet. I took a full minute to reduce the power to
> idle, watching our (newly reinstalled) JPI EDM-700 engine analyzer for
> signs of stress.
>
> As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
> off, flashing its dire warnings that EGTs had dropped beyond (and
> faster) than recommended limits. (I can't remember what the threshold
> is for that alarm -- it's preset.)
>
> This despite my most careful power reduction, which (obviously) wasn't
> slow enough.
>
> Since the damage (so to speak) had already been done, I continued the
> descent toward an Illinois corn field. With the harvest under way, I
> had my choice of:
>
> - Freshly harvested corn stubble, not plowed
> - Freshly harvested crops, plowed dirt
> - Unharvested corn or winter wheat
>
> I opted for the corn stubble, as the stalks would hold the soil
> together firmly and not present as much "flip force" to the landing
> gear as the plowed or unharvested field. I took it down to 200 AGL
> before applying power and heading home, satisfied that we would have
> survived and giving the farmer a nice show.
>
> For you aircraft owners who do this regularly, how slowly do you
> retard the throttle to prevent shock cooling? (I know -- does shock
> cooling really exist? For purposes of this discussion, I'll pretend
> that it does.)
>
> Given that the power reduction must be incredibly gradual, do you feel
> that this exercise is realistic? There really is no chance to
> simulate how you must "suddenly" find best glide speed (after your
> engine has presumably just crapped out), since you're gradually
> reducing your speed along with your power. Or do you put the plane
> into a shallow dive as you reduce power, so as not to lose airspeed?
>
> It's funny -- as renters we practiced this all the time. Now, after 9
> years of ownership, we haven't practiced it in ages -- and didn't even
> realize this lack until Shirl's comments in Paul's thread. Another
> good thing about "belonging" to this newsgroup...
>
> Thoughts?
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993www.AlexisParkInn.com
> "Your Aviation Destination"

I'm not an expert, but it seems to me that the important thing is to
reduce airspeed immediately when reducing power. It's the wind
whistling through an idling engine at 140 knots that's going to do
some serious shock cooling.
--
Gene Seibel
Tales of Flight - http://pad39a.com/gene/tales.html
Because I fly, I envy no one.

Jay Honeck wrote:
>> The issue with shock cooling isn't the rate of cooling per se, but
>> rather stress induced by differential cooling.
>
> Actually, I think it is the rate of cooling *and* the differential
> cooling -- if it exists at all. Like you, I am skeptical -- but am I
> willing to bet $25K on it? Nope.

How does the rate affect things? I have a masters in structural
engineering and work for a materials company so don't be afraid to get
technical. :-)

Matt

Matt Whiting > wrote:
> When I practiced in my Skylane and also in the club Arrow, I retarded
> the throttle smoothly in probably 2-3 seconds. I didn't worry about
> shock cooling and never saw any signs of distress in either the O-470 or
> the O-360.

I have an 0-320, and we probably take 3-5 seconds to smoothly retard the
throttle to idle during simulated engine failure practice. Thinking back
to the *actual* engine failure due to oil loss, the time elapsed between
seeing no oil pressure on the gauge, the initial obvious signs that the
engine was seizing (bucking and shaking), and the time it quit
completely was probably a total of 10 seconds. So comparing the
simulated engine failure to THAT type of actual engine failure, taking 5
seconds to retard the throttle is NOT out of the realm of realism or
accuracy with regard to simulated practice.

To Jay, do you monitor your engine analyzer when you go from cruise
power into the pattern and then pull the throttle back during your
approach? How gradually do you pull power back there, and how do the
temps on the analyzer compare to what you did in the simulated
engine-out practice?

Shirl

Matt Whiting > wrote:
> Jay Honeck wrote:
> >> The issue with shock cooling isn't the rate of cooling per se, but
> >> rather stress induced by differential cooling.
> >
> > Actually, I think it is the rate of cooling *and* the differential
> > cooling -- if it exists at all. Like you, I am skeptical -- but am I
> > willing to bet $25K on it? Nope.

> How does the rate affect things? I have a masters in structural
> engineering and work for a materials company so don't be afraid to get
> technical. :-)

It doesn't (in metals) unless the temperature change is very high and
very localized as in welding.


--
Jim Pennino

Remove .spam.sux to reply.

Gene Seibel > wrote:

> I'm not an expert, but it seems to me that the important thing is to
> reduce airspeed immediately when reducing power. It's the wind
> whistling through an idling engine at 140 knots that's going to do
> some serious shock cooling.
> --
> Gene Seibel
> Tales of Flight - http://pad39a.com/gene/tales.html
> Because I fly, I envy no one.

Which is what you are supposed to do anyway in an engine out; immediately
reduce airspeed to best glide.

--
Jim Pennino

Remove .spam.sux to reply.

wrote:
> Matt Whiting > wrote:
>> Jay Honeck wrote:
>>>> The issue with shock cooling isn't the rate of cooling per se, but
>>>> rather stress induced by differential cooling.
>>> Actually, I think it is the rate of cooling *and* the differential
>>> cooling -- if it exists at all. Like you, I am skeptical -- but am I
>>> willing to bet $25K on it? Nope.
>
>> How does the rate affect things? I have a masters in structural
>> engineering and work for a materials company so don't be afraid to get
>> technical. :-)
>
> It doesn't (in metals) unless the temperature change is very high and
> very localized as in welding.

That's my understanding also, but I wanted to see Jay's information.
Maybe he's found some phenomenon I'm not aware of.

Matt

> To Jay, do you monitor your engine analyzer when you go from cruise
> power into the pattern and then pull the throttle back during your
> approach? How gradually do you pull power back there, and how do the
> temps on the analyzer compare to what you did in the simulated
> engine-out practice?

Yep. The shock-cooling alarm never goes off during a regular
approach, because of the gradual nature of things. By the time we
enter downwind, we've got the prop and mixture full forward, and are
adjusting manifold pressure (throttle) only slightly to control
airspeed. We're looking for 100 mph/90 knots on downwind.

This wind-down from cruise speed (160 mph/140 knots) usually takes
several minutes, unless we're being asked to keep our speed up at a
controlled field. We generally carry power into the flare (hey, it's
a Cherokee, and a nose-heavy one at that), slowly retarding power as
we touch down.

Apparently this procedure (which we do without thinking about it) is
engine-friendly enough to keep the temperature rate-of-decline outside
of the shock cooling alarm's parameters.

In the future I think we'll practice slow flight (which mimics this
whole engine management procedure) before practicing engine-out
stuff. That should prevent the whole shock-cooling problem,
methinks.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

> >> The issue with shock cooling isn't the rate of cooling per se, but
> >> rather stress induced by differential cooling.
>
> > Actually, I think it is the rate of cooling *and* the differential
> > cooling -- if it exists at all. Like you, I am skeptical -- but am I
> > willing to bet $25K on it? Nope.
>
> How does the rate affect things? I have a masters in structural
> engineering and work for a materials company so don't be afraid to get
> technical. :-)

How 'bout this: It's the disparate rates of cooling in some parts of
the engine (versus others) that causes the differential cooling that
induces stress?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay Honeck wrote:
>>>> The issue with shock cooling isn't the rate of cooling per se, but
>>>> rather stress induced by differential cooling.
>>> Actually, I think it is the rate of cooling *and* the differential
>>> cooling -- if it exists at all. Like you, I am skeptical -- but am I
>>> willing to bet $25K on it? Nope.
>> How does the rate affect things? I have a masters in structural
>> engineering and work for a materials company so don't be afraid to get
>> technical. :-)
>
> How 'bout this: It's the disparate rates of cooling in some parts of
> the engine (versus others) that causes the differential cooling that
> induces stress?

Yes, that is what I said originally. It is differential cooling that
causes the problem, not the rate of cooling itself. If you could cool
the entire engine uniformly, I don't think it would matter much how fast
you cooled it.

It isn't the rate itself that causes a problem, it is the difference in
rates from one location to another. However, I still think that the
greatest thermally induced stress occurs during the initial heat-up from
a cold start, but I don't have any data to confirm that and I don't have
an instrument airplane with which to collect the data.

Matt

A slow reduction in power setting certainly isn't realistic. I've had a few
power failures in my time (all in twins) and in every case the loss was
fairly sudden. I've never run out of fuel, but I have run a tank almost dry
on purpose, and the associated coughing and sputtering gave me plenty of
warning.

Bob Gardner

"Jay Honeck" > wrote in message
ups.com...
> As previously noted (in the thread about Paul's wife getting scared),
> Mary and I had virtually stopped doing this kind of flying for fear of
> harming our (very expensive) engine. A lively debate ensued as to
> whether or not repeated high-to-low-to-high power applications would
> wear out your engine any faster than would normal operations.
>
> I eventually agreed that gradual power changes would not unduly harm
> an air-cooled engine, and vowed that I would endeavor to practice this
> most-important skill on our next flight. And we did.
>
> We were on a flight back from Galesburg, IL when I started the
> procedure, and very gradually began a power reduction whilst in cruise
> flight at 3500 feet. I took a full minute to reduce the power to
> idle, watching our (newly reinstalled) JPI EDM-700 engine analyzer for
> signs of stress.
>
> As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
> off, flashing its dire warnings that EGTs had dropped beyond (and
> faster) than recommended limits. (I can't remember what the threshold
> is for that alarm -- it's preset.)
>
> This despite my most careful power reduction, which (obviously) wasn't
> slow enough.
>
> Since the damage (so to speak) had already been done, I continued the
> descent toward an Illinois corn field. With the harvest under way, I
> had my choice of:
>
> - Freshly harvested corn stubble, not plowed
> - Freshly harvested crops, plowed dirt
> - Unharvested corn or winter wheat
>
> I opted for the corn stubble, as the stalks would hold the soil
> together firmly and not present as much "flip force" to the landing
> gear as the plowed or unharvested field. I took it down to 200 AGL
> before applying power and heading home, satisfied that we would have
> survived and giving the farmer a nice show.
>
> For you aircraft owners who do this regularly, how slowly do you
> retard the throttle to prevent shock cooling? (I know -- does shock
> cooling really exist? For purposes of this discussion, I'll pretend
> that it does.)
>
> Given that the power reduction must be incredibly gradual, do you feel
> that this exercise is realistic? There really is no chance to
> simulate how you must "suddenly" find best glide speed (after your
> engine has presumably just crapped out), since you're gradually
> reducing your speed along with your power. Or do you put the plane
> into a shallow dive as you reduce power, so as not to lose airspeed?
>
> It's funny -- as renters we practiced this all the time. Now, after 9
> years of ownership, we haven't practiced it in ages -- and didn't even
> realize this lack until Shirl's comments in Paul's thread. Another
> good thing about "belonging" to this newsgroup...
>
> Thoughts?
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"
>

In article . com>,
Jay Honeck > wrote:


> In the future I think we'll practice slow flight (which mimics this
> whole engine management procedure) before practicing engine-out
> stuff. That should prevent the whole shock-cooling problem,
> methinks.

Slow flight might increase the problem. You're mushing along with poor
flow through the cowling, low airspeed and using power...perhaps you're
going to increase engine temp. over cruise.

As for the analyzer warning. I had one on my 182 when hauling jumpers.
Just pushing the nose over at the top of the climb *without reducing
power* would result in a "shock cooling" alarm, just the increase in
airspeed created a cooling rate that exceeds the limits. I quickly
learned to ignore the shock cooling warning.

Trainer aircraft are flown hard all the time. Students/renters cram the
power in on takeoff and yank it to idle on downwind time after time.
Those engines last well.

I flew jumpers for 17 years in 182s and 206s. With the exception of one
airplane flown by an idiot (this guy would cram the power in right after
start with no warmup) we didn't have to replace cylinders, engines went
TBO or beyond.

From my experience more damage is done on power increases than
reduction. Be as gentle as you can to your engine but don't go crazy
about the shock cooling thing.

"Jay Honeck" > wrote in message
ups.com...
> As previously noted (in the thread about Paul's wife getting scared),
> Mary and I had virtually stopped doing this kind of flying for fear of
> harming our (very expensive) engine. A lively debate ensued as to
> whether or not repeated high-to-low-to-high power applications would
> wear out your engine any faster than would normal operations.


Jay, the cylinder barrels on your engine are steel with air-cooling fins
attached. Your pistons and cylinder heads are aluminum alloy. The two
metals will expand and contract at different rates when heated or cooled.
Think about the way the thermostat in your house works. A bi-metal strip
(strip of metal composed of one type of metal on one side and another type
on the other), when heated or cooled bends because of the different
expansion rates of the two metals. When I think of shock cooling I think of
the sudden removal of the heat source (abrupt power reduction) along with
the different metals contraction rate (steel with air blowing over it's
cooling fins versus aluminum inside the barrel with hot oil being sprayed on
it). It is easy for me to visualize the scuffing that can occur because of
the reduced clearances as the barrel contracts onto the piston. The same in
reverse would hold true for shock heating.

Whether any of this is true I don't know, but I am with you that gradual
increase or reduction of power seems less likely to cause damage to an
aircooled engine.

--
*H. Allen Smith*
WACO - We are all here, because we are not all there.

"Jay Honeck" > wrote in message
ups.com...
> As previously noted (in the thread about Paul's wife getting scared),
> Mary and I had virtually stopped doing this kind of flying for fear of
> harming our (very expensive) engine. A lively debate ensued as to
> whether or not repeated high-to-low-to-high power applications would
> wear out your engine any faster than would normal operations.
>
> I eventually agreed that gradual power changes would not unduly harm
> an air-cooled engine, and vowed that I would endeavor to practice this
> most-important skill on our next flight. And we did.
>
> We were on a flight back from Galesburg, IL when I started the
> procedure, and very gradually began a power reduction whilst in cruise
> flight at 3500 feet. I took a full minute to reduce the power to
> idle, watching our (newly reinstalled) JPI EDM-700 engine analyzer for
> signs of stress.
>
> As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
> off, flashing its dire warnings that EGTs had dropped beyond (and
> faster) than recommended limits. (I can't remember what the threshold
> is for that alarm -- it's preset.)
>
> This despite my most careful power reduction, which (obviously) wasn't
> slow enough.
....
>
> Thoughts?

You're worrying about virtually nothing!
http://www.avweb.com/news/maint/182883-1.html

Shock Cooling: Myth or Reality?

Powerplant management guru Kas Thomas of TBO ADVISOR examines the physics
and metallurgy of "shock cooling" and concludes that, contrary to the
conventional wisdom, it is not a major contributor to cylinder head
cracking.

What were your CHTs?

Matt Whiting > wrote:
> Jay Honeck wrote:
> >>>> The issue with shock cooling isn't the rate of cooling per se, but
> >>>> rather stress induced by differential cooling.
> >>> Actually, I think it is the rate of cooling *and* the differential
> >>> cooling -- if it exists at all. Like you, I am skeptical -- but am I
> >>> willing to bet $25K on it? Nope.
> >> How does the rate affect things? I have a masters in structural
> >> engineering and work for a materials company so don't be afraid to get
> >> technical. :-)
> >
> > How 'bout this: It's the disparate rates of cooling in some parts of
> > the engine (versus others) that causes the differential cooling that
> > induces stress?

> Yes, that is what I said originally. It is differential cooling that
> causes the problem, not the rate of cooling itself. If you could cool
> the entire engine uniformly, I don't think it would matter much how fast
> you cooled it.

> It isn't the rate itself that causes a problem, it is the difference in
> rates from one location to another. However, I still think that the
> greatest thermally induced stress occurs during the initial heat-up from
> a cold start, but I don't have any data to confirm that and I don't have
> an instrument airplane with which to collect the data.

> Matt

I would think the greatest thermally induced stress occurs when you fly
into rain.

--
Jim Pennino

Remove .spam.sux to reply.

Matt Barrow schrieb:

> You're worrying about virtually nothing!
> http://www.avweb.com/news/maint/182883-1.html
>
> Shock Cooling: Myth or Reality?
>
> Powerplant management guru Kas Thomas of TBO ADVISOR examines the physics
> and metallurgy of "shock cooling" and concludes that, contrary to the
> conventional wisdom, it is not a major contributor to cylinder head
> cracking.

Lycoming says otherwise:
http://www.lycoming.textron.com/support/tips-advice/key-reprints/pdfs/Key%20Operations.pdf

<Lycoming>
Sudden cooling is detrimental to the good health of the piston aircraft
engine. Lycoming Service Instruction 1094D recommends a maximum
temperature change of 50° F per minute to avoid shock-cooling of the
cylinders.

Operations that tend to induce rapid engine cooldown are
often associated with a fast letdown and return to the field after
dropping parachutists or a glider tow. There are occasions when Air
Traffic Control also calls for fast descents that may lead to sudden
cooling.

The engine problems that may be expected when pilots consistently
make fast letdowns with little or no power include:

1. Excessively worn ring grooves accompanied by broken rings.
2. Cracked cylinder heads.
3. Warped exhaust valves.
4. Bent pushrods.
5. Spark plug fouling.
</Lycoming>


Be aware that "powerplant management guru Kas Thomas" won't buy you a
new engine if you happen do damage yours by following his recomendations.

It's every operator's choice whether he prefers to believe the engine
manufactorer or some guru.

Stefan

Jay:
> > In the future I think we'll practice slow flight (which mimics this
> > whole engine management procedure) before practicing engine-out
> > stuff. That should prevent the whole shock-cooling problem,
> > methinks.

Dale:
> Slow flight might increase the problem. You're mushing along with poor
> flow through the cowling, low airspeed and using power...perhaps you're
> going to increase engine temp. over cruise.

That was my first thought, that slow flight would increase temp and,
therefore, how would it prevent the shock-cooling problem (if indeed it
is one)?

"Stefan" > wrote in message
...
> Matt Barrow schrieb:
>
>> You're worrying about virtually nothing!
>> http://www.avweb.com/news/maint/182883-1.html
>>
>> Shock Cooling: Myth or Reality?
>>
>> Powerplant management guru Kas Thomas of TBO ADVISOR examines the physics
>> and metallurgy of "shock cooling" and concludes that, contrary to the
>> conventional wisdom, it is not a major contributor to cylinder head
>> cracking.
>
> Lycoming says otherwise:
> http://www.lycoming.textron.com/support/tips-advice/key-reprints/pdfs/Key%20Operations.pdf
>
> <Lycoming>
> Sudden cooling is detrimental to the good health of the piston aircraft
> engine. Lycoming Service Instruction 1094D recommends a maximum
> temperature change of 50° F per minute to avoid shock-cooling of the
> cylinders.

Thomas offers data and evidence, Lycoming offers anecdote and legend.

Takes yer picks.

Matt Barrow schrieb:

> Thomas offers data and evidence, Lycoming offers anecdote and legend.

Lycoming offers running engines. Thomas offers words.

"Stefan" > wrote in message
.. .
> Matt Barrow schrieb:
>
>> Thomas offers data and evidence, Lycoming offers anecdote and legend.
>
> Lycoming offers running engines. Thomas offers words.

Try something other than "Argument from Authority", such as EVIDENCE.

Or, if you can show that Lycoming HAS NOT been shown to frequently be FOS,
then you can make their case.

Matt Barrow schrieb:

>>> Thomas offers data and evidence, Lycoming offers anecdote and legend.
>> Lycoming offers running engines. Thomas offers words.

> Try something other than "Argument from Authority", such as EVIDENCE.

Evidently, Lycoming knows how to build engines. Evidently, Lycoming has
a lot of experience by looking at used engines while overhawling them. I
don't know how many engines Thomas has built or overhauled. I don't even
know where his data comes from and how it was collected.

> Or, if you can show that Lycoming HAS NOT been shown to frequently be FOS,

No idea what a FOS should be. Please write in a language I understand.

> then you can make their case.

I'm not making anyone's case. In fact, I couldn't care less, as I'm
happy enough to operate a liquid cooled engine with 21th century technology.

"Stefan" > wrote in message
. ..
> Matt Barrow schrieb:
>
>>>> Thomas offers data and evidence, Lycoming offers anecdote and legend.
>>> Lycoming offers running engines. Thomas offers words.
>
>> Try something other than "Argument from Authority", such as EVIDENCE.
>
> Evidently, Lycoming knows how to build engines. Evidently, Lycoming has a
> lot of experience by looking at used engines while overhawling them. I
> don't know how many engines Thomas has built or overhauled. I don't even
> know where his data comes from and how it was collected.

Lycoming's take is based on legal protection of it's assets, not the engine
owners.

>
>> Or, if you can show that Lycoming HAS NOT been shown to frequently be
>> FOS,
>
> No idea what a FOS should be. Please write in a language I understand.

It took them quite a while to recognize the :OP was not a disaster in the
making. GAMI's engine stand data pretty much showed both Lycoming and TCM to
be way off base. GAMI did years of hard research, Lyc and TCM did their
appraisals based on what their legal counsel recommended, not their
engineers (who evidently didn;t even understand the engine stroke sequence.)

>
>> then you can make their case.
>
> I'm not making anyone's case. In fact, I couldn't care less, as I'm happy
> enough to operate a liquid cooled engine with 21th century technology.

A heavier engine is SOTA?

Also, how does a liquid cooled engine vary from the physics of an engine
sequence?

No small wonder that aviation is the home of so many myths, legends, and
OWT's.

--
Matt Barrow
Performance Homes, LLC.
Cheyenne, WY

wrote:
> Matt Whiting > wrote:
>> Jay Honeck wrote:
>>>>>> The issue with shock cooling isn't the rate of cooling per se, but
>>>>>> rather stress induced by differential cooling.
>>>>> Actually, I think it is the rate of cooling *and* the differential
>>>>> cooling -- if it exists at all. Like you, I am skeptical -- but am I
>>>>> willing to bet $25K on it? Nope.
>>>> How does the rate affect things? I have a masters in structural
>>>> engineering and work for a materials company so don't be afraid to get
>>>> technical. :-)
>>> How 'bout this: It's the disparate rates of cooling in some parts of
>>> the engine (versus others) that causes the differential cooling that
>>> induces stress?
>
>> Yes, that is what I said originally. It is differential cooling that
>> causes the problem, not the rate of cooling itself. If you could cool
>> the entire engine uniformly, I don't think it would matter much how fast
>> you cooled it.
>
>> It isn't the rate itself that causes a problem, it is the difference in
>> rates from one location to another. However, I still think that the
>> greatest thermally induced stress occurs during the initial heat-up from
>> a cold start, but I don't have any data to confirm that and I don't have
>> an instrument airplane with which to collect the data.
>
>> Matt
>
> I would think the greatest thermally induced stress occurs when you fly
> into rain.
>

That may well be, but probably only for the front two cylinders. I
wonder if the front cylinders have a higher failure rate than the rest?

Matt

Stefan wrote:
> Matt Barrow schrieb:
>
>> Thomas offers data and evidence, Lycoming offers anecdote and legend.
>
> Lycoming offers running engines. Thomas offers words.

And Lycoming benefits if your engine lasts fewer hours.

Matt

Matt Barrow schrieb:

>> I'm not making anyone's case. In fact, I couldn't care less, as I'm happy
>> enough to operate a liquid cooled engine with 21th century technology.
>
> A heavier engine is SOTA?

You have not the slightest idea what engine I'm talking about, yet you
know that it's heavier. Wow. Now if everything else you wrote is based
on the same profound knowledge, I better skip your comments.

Matt Whiting schrieb:

> And Lycoming benefits if your engine lasts fewer hours.

So avoiding shock cooling actually lowers its life span? Wow.

Matt Whiting > wrote:
> wrote:
> > Matt Whiting > wrote:
> >> Jay Honeck wrote:
> >>>>>> The issue with shock cooling isn't the rate of cooling per se, but
> >>>>>> rather stress induced by differential cooling.
> >>>>> Actually, I think it is the rate of cooling *and* the differential
> >>>>> cooling -- if it exists at all. Like you, I am skeptical -- but am I
> >>>>> willing to bet $25K on it? Nope.
> >>>> How does the rate affect things? I have a masters in structural
> >>>> engineering and work for a materials company so don't be afraid to get
> >>>> technical. :-)
> >>> How 'bout this: It's the disparate rates of cooling in some parts of
> >>> the engine (versus others) that causes the differential cooling that
> >>> induces stress?
> >
> >> Yes, that is what I said originally. It is differential cooling that
> >> causes the problem, not the rate of cooling itself. If you could cool
> >> the entire engine uniformly, I don't think it would matter much how fast
> >> you cooled it.
> >
> >> It isn't the rate itself that causes a problem, it is the difference in
> >> rates from one location to another. However, I still think that the
> >> greatest thermally induced stress occurs during the initial heat-up from
> >> a cold start, but I don't have any data to confirm that and I don't have
> >> an instrument airplane with which to collect the data.
> >
> >> Matt
> >
> > I would think the greatest thermally induced stress occurs when you fly
> > into rain.
> >

> That may well be, but probably only for the front two cylinders. I
> wonder if the front cylinders have a higher failure rate than the rest?

> Matt

Hmmm, thinking about it a bit, any shock cooling should be worse on
the front two cylinders rain or shine.

An analyse of failure rate by cylinder position would be interesting.

--
Jim Pennino

Remove .spam.sux to reply.

wrote:
> Matt Whiting > wrote:
>> wrote:
>>> Matt Whiting > wrote:
>>>> Jay Honeck wrote:
>>>>>>>> The issue with shock cooling isn't the rate of cooling per se, but
>>>>>>>> rather stress induced by differential cooling.
>>>>>>> Actually, I think it is the rate of cooling *and* the differential
>>>>>>> cooling -- if it exists at all. Like you, I am skeptical -- but am I
>>>>>>> willing to bet $25K on it? Nope.
>>>>>> How does the rate affect things? I have a masters in structural
>>>>>> engineering and work for a materials company so don't be afraid to get
>>>>>> technical. :-)
>>>>> How 'bout this: It's the disparate rates of cooling in some parts of
>>>>> the engine (versus others) that causes the differential cooling that
>>>>> induces stress?
>>>> Yes, that is what I said originally. It is differential cooling that
>>>> causes the problem, not the rate of cooling itself. If you could cool
>>>> the entire engine uniformly, I don't think it would matter much how fast
>>>> you cooled it.
>>>> It isn't the rate itself that causes a problem, it is the difference in
>>>> rates from one location to another. However, I still think that the
>>>> greatest thermally induced stress occurs during the initial heat-up from
>>>> a cold start, but I don't have any data to confirm that and I don't have
>>>> an instrument airplane with which to collect the data.
>>>> Matt
>>> I would think the greatest thermally induced stress occurs when you fly
>>> into rain.
>>>
>
>> That may well be, but probably only for the front two cylinders. I
>> wonder if the front cylinders have a higher failure rate than the rest?
>
>> Matt
>
> Hmmm, thinking about it a bit, any shock cooling should be worse on
> the front two cylinders rain or shine.
>
> An analyse of failure rate by cylinder position would be interesting.
>

Yes, my thought exactly. I wonder if anyone keeps such data? I know
when I owned my Skylane, we never had any unusual issues with the front
two cylinders. This data, if available, would certainly provide some
indication if shock cooling is real or imagined.

Matt

Stefan wrote:
> Matt Whiting schrieb:
>
>> And Lycoming benefits if your engine lasts fewer hours.
>
> So avoiding shock cooling actually lowers its life span? Wow.

You have no evidence that following Lycoming's recommendations avoids
the mythical shock cooling demon or that it lengthens engine life. My
experience is that the engines that are run the hardest also last the
longest. I'm basing this on everything from chainsaws to lawnmowers to
motorcycles to cars to trucks to off-road heavy equipment (dozers,
skidders, etc.) to airplanes (trainers, air taxi operations, cargo).

I'm personally not convinced that Lycoming's recommendations lengthen
engine life.

Matt

In article >,
wrote:


>
> Hmmm, thinking about it a bit, any shock cooling should be worse on
> the front two cylinders rain or shine.


It was the rear cylinders that would alarm on my monitor. They're
hotter and are the farthest from ambient temp.

Stefan wrote:

> Lycoming says otherwise:


The engine manufacturers are about the last place I'd look for engine
management techniques.

Stefan wrote:
> Matt Barrow schrieb:
>
>> Thomas offers data and evidence, Lycoming offers anecdote and legend.
>
> Lycoming offers running engines. Thomas offers words.


Lycoming and Continental offer no science whatsoever to back up their
recommendations. There are several companies that can show you hard
scientific data to disprove what the engine manufacturers claim.

"Matt Whiting" > wrote

> The issue with shock cooling isn't the rate of cooling per se, but rather
> stress induced by differential cooling. Most engines see far higher
> temperature differentials during start-up than they do during cooldown.
> Jay, have you timed your engine heat up rate? It would be interesting to
> watch how fast your engine heats up from say a 50 degree cold start and
> then compare that to the cool-down rate when you pull the throttle for
> engine out practice. I'm assuming this would be fairly trivial with your
> engine analyzer.

I'm pretty sure that the rate of heating of the metal of the head is not
the big issue, according to the shock cooling proponents.

Instead, it is the heads (and cylinders) cooling more rapidly than the
pistons, and the hot pistons (not able to be cooled as rapidly) against the
cooler cylinders (the cylinders do not have heat instrumentation, so the
closest thing they can do is to measure is the head temperatures) causing a
reduction in the tolerances between the piston and the cylinder walls, thus
causing possible scuffing and abnormal wear.

At least that is my take on what they say.
--
Jim in NC

"Morgans" wrote

> At least that is my take on what they say.

I should have added that the cylinders heating up faster, on start up,
than the pistons would increase the tolerances, and thus cause no scuffing.
--
Jim in NC

In article >,
Matt Whiting > wrote:

> > Hmmm, thinking about it a bit, any shock cooling should be worse on
> > the front two cylinders rain or shine.
> >
> > An analyse of failure rate by cylinder position would be interesting.
> >
>
> Yes, my thought exactly. I wonder if anyone keeps such data? I know
> when I owned my Skylane, we never had any unusual issues with the front
> two cylinders. This data, if available, would certainly provide some
> indication if shock cooling is real or imagined.

My O-320 had 2 cracked cylinders (both on the left side) at the same
time. This was the year after the exhaust stud hold cracked on
the right front cylinder. Shock cooling? More likely due to the fact
that these were cermichromed cylinders with an unknown number
of hours on them before they cracked at <600hours SMOH.

--
Bob Noel
(goodness, please trim replies!!!)

"Matt Whiting" > wrote in message
...
> Jay Honeck wrote:
>>> The issue with shock cooling isn't the rate of cooling per se, but
>>> rather stress induced by differential cooling.
>>
>> Actually, I think it is the rate of cooling *and* the differential
>> cooling -- if it exists at all. Like you, I am skeptical -- but am I
>> willing to bet $25K on it? Nope.
>
> How does the rate affect things? I have a masters in structural
> engineering and work for a materials company so don't be afraid to get
> technical. :-)
>
> Matt

By implication, a fast cooling rate would cause *more* differential cooling,
since the cylinders cool from the fins inward. The faster the cooling, the
higher the delta-T between the internal and external surfaces of the
cylinders. The higher the delta, the more internal stresses on the cylinders
due to the different growth between the hot and cold surfaces.

But you already knew that and were just being difficult, eh?

KB

Kyle Boatright wrote:
> "Matt Whiting" > wrote in message
> ...
>> Jay Honeck wrote:
>>>> The issue with shock cooling isn't the rate of cooling per se, but
>>>> rather stress induced by differential cooling.
>>> Actually, I think it is the rate of cooling *and* the differential
>>> cooling -- if it exists at all. Like you, I am skeptical -- but am I
>>> willing to bet $25K on it? Nope.
>> How does the rate affect things? I have a masters in structural
>> engineering and work for a materials company so don't be afraid to get
>> technical. :-)
>>
>> Matt
>
> By implication, a fast cooling rate would cause *more* differential cooling,
> since the cylinders cool from the fins inward. The faster the cooling, the
> higher the delta-T between the internal and external surfaces of the
> cylinders. The higher the delta, the more internal stresses on the cylinders
> due to the different growth between the hot and cold surfaces.
>
> But you already knew that and were just being difficult, eh?

It is a subtle point maybe, but an important one. It isn't the rate of
cooling that matters. It is a difference in rate between two locations.
Faster cooling doesn't necessarily a greater differential, it all
depends on how the cooling is done.

In some materials and at some temperatures, the rate of cooling can
change the fundamental material properties. That is a different issue
than what is involved with engines.

Matt

Morgans wrote:
> "Matt Whiting" > wrote
>
>> The issue with shock cooling isn't the rate of cooling per se, but rather
>> stress induced by differential cooling. Most engines see far higher
>> temperature differentials during start-up than they do during cooldown.
>> Jay, have you timed your engine heat up rate? It would be interesting to
>> watch how fast your engine heats up from say a 50 degree cold start and
>> then compare that to the cool-down rate when you pull the throttle for
>> engine out practice. I'm assuming this would be fairly trivial with your
>> engine analyzer.
>
> I'm pretty sure that the rate of heating of the metal of the head is not
> the big issue, according to the shock cooling proponents.
>
> Instead, it is the heads (and cylinders) cooling more rapidly than the
> pistons, and the hot pistons (not able to be cooled as rapidly) against the
> cooler cylinders (the cylinders do not have heat instrumentation, so the
> closest thing they can do is to measure is the head temperatures) causing a
> reduction in the tolerances between the piston and the cylinder walls, thus
> causing possible scuffing and abnormal wear.
>
> At least that is my take on what they say.

It seems to me that upon engine start the pistons would heat up much
faster than the cylinders causing the same net affect as cooling down
the cylinders faster once hot. Either way the pistons are hotter than
the cylinders.


Matt

Morgans wrote:
> "Morgans" wrote
>
>> At least that is my take on what they say.
>
> I should have added that the cylinders heating up faster, on start up,
> than the pistons would increase the tolerances, and thus cause no scuffing.

Why would the cylinders heat up faster? Only the very top of the
cylinder is in constant contact with the combustion heat whereas the top
of the piston is entirely in contact. As you go down the cylinder away
from the head, the cylinder spends less and less time in contact with
the combustion heat and thus will be cooler.

Matt

Jay Honeck wrote:

>
> For you aircraft owners who do this regularly, how slowly do you
> retard the throttle to prevent shock cooling? (I know -- does shock
> cooling really exist? For purposes of this discussion, I'll pretend
> that it does.)


I don't believe it exists so I'll go from a low cruise power setting of
say 20-21" and 2300 rpm to throttle fully retarded in 3-5 seconds.



>
> Given that the power reduction must be incredibly gradual, do you feel
> that this exercise is realistic?


Doing it your way? No.




There really is no chance to
> simulate how you must "suddenly" find best glide speed (after your
> engine has presumably just crapped out), since you're gradually
> reducing your speed along with your power. Or do you put the plane
> into a shallow dive as you reduce power, so as not to lose airspeed?


Your just going to have to be content that you are unwilling to
realisticly practice this. Find yourself a friends private dirt strip
field and start 5-7 miles away at 3000 AGL and land on it without
touching the power after you have gone to idle. Another thing I do all
the time is pull the power to idle on the downwind and land without
touching the power.

"Matt Whiting" > wrote
>
> Why would the cylinders heat up faster? Only the very top of the cylinder
> is in constant contact with the combustion heat whereas the top of the
> piston is entirely in contact. As you go down the cylinder away from the
> head, the cylinder spends less and less time in contact with the
> combustion heat and thus will be cooler.

Perhaps they would not. I was going simply on the converse.

My thought is that the cold oil shooting on the piston, and a relatively
weak combustion would keep the piston cooler.
--
Jim in NC

Stefan,

> Evidently, Lycoming knows how to build engines
>

Oh? The AD record seems to indicate otherwise.

--
Thomas Borchert (EDDH)

Matt Whiting > wrote in news:foeQi.309$2n4.18956
@news1.epix.net:

> Stefan wrote:
>> Matt Whiting schrieb:
>>
>>> And Lycoming benefits if your engine lasts fewer hours.
>>
>> So avoiding shock cooling actually lowers its life span? Wow.
>
> You have no evidence that following Lycoming's recommendations avoids
> the mythical shock cooling demon or that it lengthens engine life. My
> experience is that the engines that are run the hardest also last the
> longest. I'm basing this on everything from chainsaws to lawnmowers
to
> motorcycles to cars to trucks to off-road heavy equipment (dozers,
> skidders, etc.) to airplanes (trainers, air taxi operations, cargo).
>
> I'm personally not convinced that Lycoming's recommendations lengthen
> engine life.
>
> Matt



Shock cooling isn't mythical. It's a fact. It's a physical law.

Any component subject to heating is subject to this law. If you take a
piece of metal and heat it rapidly on one side, that side will expand
more rapidly than the other. This gradient of temp will cause a
difference in physical size one side to the other. The elastic stress
induced by this is cyclically compounded and the resultant locked stress
points that build up in the material, particularly if it's a brittle
material like cast iron, will eventually fail, given time.
The speed at which these stresses are imposed are critical. Speed
because if you introduce the heat gradually (decrease the speed of the
overall temp change), it's given a chance to get to the other side and
expand the other side at a rate not quite so dramatically different as
the side the heat is applied to. Simple eh?
The quicker you insert heat on one side of the material, the greater the
load on the opposite side and the more likely minor damage events
(cracks on a near molecular leve) are occuring. These tiny bits of
damage will become stress risers for the next time th ematerial is
loaded and the cracks will continue to expand until a failure of the
component occurs.


I think Lycoming probably figured most of this out in the 1920s,
Continental even earlier.

However, if it's anectodal evidence that is required...
I've worked for recip operators where this was a daily problem. In
glider tugs, for instance, jug failures were common. Operations had to
be tailered to minimise the strain, and these adopted procedures worked.
I've also flown big recips and they also required careful management to
avoid blowing the top of a jug off. The emphasis is always on minimising
the speed at which th etemps change.
Jets are no different. Blades ae subject ot enoromous thermal stresses,
and all of the procedures laid down by the manufacturers are designed to
extend engine life as much as possible. Everything from engine startup,
through warmup times to takeoff (admittedly not all manufacturers have
done this over the years and there are other reasons for this) to
reduced power for climb to care in reduction of power at top of descent
are all used to this end.


Other bugbears of the punished engine are micro-seizures and excessive
friction due to reduced or even sometimes increased, clearances due to
rapid temp changes.

If the aircraft is being manuevered violently along with rapid power
changes, you can add precession to the damage being caused.In
aerobatics, obviously.
That is why, even though the pilot must be prompt with his power
changes to maintain control of his speed, it is accepted that it is best
practice to make these changes as smoothly and deliberately as possible
whilst still meeting the demands of aircraft control.
But even relatively mild manuevering combined with rapid throttle
changes will induce the same stresses to a lesser degree and are
therefore undesirable.

None of this is new info , of course. I have engine operating manuals
from the 1930s that address all of these issues and modern manuals
remain pretty much the same. These principles were understood long
before that. Interestingly though, I have a workshop manual for a 1933
Le Blond that talks about corrosion on the inside of a hollow crank,
it's causes and prevention, all of which could directly apply to that
debacle with lycomings. Seems some lessons have been forgotten!
The manufaturers have no interest in misleading anyone into screwing
their engines up to increase their profits. They rely on their
reputations as builders of reliable engines to increase their sales.
An engine that never makes it to TBO would be a liability to them..
Want to increase your engine life and reliability? Don't bash your
throttle around.

For real improvement in addition to these suggestions, install a pre-
oiler and oil heater. Your bottom end will last forever and the top will
be much improved as well. If you're operating on condition you might get
double the TBO overall or more! A really good filter is essential for
longevity as well.Get an STC for one if there's not one readily
available for your airplane..



Bertie

Stefan > wrote in
:

> Matt Barrow schrieb:
>
>>>> Thomas offers data and evidence, Lycoming offers anecdote and
>>>> legend.
>>> Lycoming offers running engines. Thomas offers words.
>
>> Try something other than "Argument from Authority", such as EVIDENCE.
>
> Evidently, Lycoming knows how to build engines. Evidently, Lycoming
> has a lot of experience by looking at used engines while overhawling
> them. I don't know how many engines Thomas has built or overhauled. I
> don't even know where his data comes from and how it was collected.
>
>> Or, if you can show that Lycoming HAS NOT been shown to frequently be
>> FOS,
>
> No idea what a FOS should be. Please write in a language I understand.
>
>> then you can make their case.
>
> I'm not making anyone's case. In fact, I couldn't care less, as I'm
> happy enough to operate a liquid cooled engine with 21th century
> technology.
>


Actually, that engine is 19th century technology with some cute and badly
thought out curliecues added.


Bertie

Stefan,

And two more thoughts:

> Evidently, Lycoming knows how to build engines.

Which doesn't directly mean anything with regard to operating them.

> Evidently, Lycoming has
> a lot of experience by looking at used engines while overhawling them.

Which, again, doesn't directly say much about why they need overhauling.
That cracked cylinder head doesn't come with a sign next to the crack
reading "I was caused by shock cooling".

--
Thomas Borchert (EDDH)

Bertie the Bunyip wrote:
> Matt Whiting > wrote in news:foeQi.309$2n4.18956
> @news1.epix.net:
>
>> Stefan wrote:
>>> Matt Whiting schrieb:
>>>
>>>> And Lycoming benefits if your engine lasts fewer hours.
>>> So avoiding shock cooling actually lowers its life span? Wow.
>> You have no evidence that following Lycoming's recommendations avoids
>> the mythical shock cooling demon or that it lengthens engine life. My
>> experience is that the engines that are run the hardest also last the
>> longest. I'm basing this on everything from chainsaws to lawnmowers
> to
>> motorcycles to cars to trucks to off-road heavy equipment (dozers,
>> skidders, etc.) to airplanes (trainers, air taxi operations, cargo).
>>
>> I'm personally not convinced that Lycoming's recommendations lengthen
>> engine life.
>>
>> Matt
>
>
>
> Shock cooling isn't mythical. It's a fact. It's a physical law.

A physical law, eh? I've had 8 years of engineering school and haven't
seen this law. Can you provide a reference to the law of shock cooling?
I searched for the "law of shock cooling" in Google and came up empty...


> Any component subject to heating is subject to this law. If you take a
> piece of metal and heat it rapidly on one side, that side will expand
> more rapidly than the other. This gradient of temp will cause a
> difference in physical size one side to the other. The elastic stress
> induced by this is cyclically compounded and the resultant locked stress
> points that build up in the material, particularly if it's a brittle
> material like cast iron, will eventually fail, given time.
> The speed at which these stresses are imposed are critical. Speed
> because if you introduce the heat gradually (decrease the speed of the
> overall temp change), it's given a chance to get to the other side and
> expand the other side at a rate not quite so dramatically different as
> the side the heat is applied to. Simple eh?
> The quicker you insert heat on one side of the material, the greater the
> load on the opposite side and the more likely minor damage events
> (cracks on a near molecular leve) are occuring. These tiny bits of
> damage will become stress risers for the next time th ematerial is
> loaded and the cracks will continue to expand until a failure of the
> component occurs.

Yes, I'm well aware of thermal expansion and its affects. When an
engine is pulled to idle, the cylinders and heads are getting cooled
from both sides, the outside via airflow and the inside via airflow
through the engine. The far greater differential is under full throttle
during the first take-off when the engine has not yet reached thermal
equilibrium and you are heating it intensely on the inside and cooling
it on the outside.

If people wanted to talk about shock heating, then I'd be much more
willing to believe them and this fits the physics a lot better in my
opinion. Shock cooling is much less an issue from both a physics
perspective and an experience perspective.

Matt

Matt Whiting > wrote in
:

> Bertie the Bunyip wrote:
>> Matt Whiting > wrote in news:foeQi.309$2n4.18956
>> @news1.epix.net:
>>
>>> Stefan wrote:
>>>> Matt Whiting schrieb:
>>>>
>>>>> And Lycoming benefits if your engine lasts fewer hours.
>>>> So avoiding shock cooling actually lowers its life span? Wow.
>>> You have no evidence that following Lycoming's recommendations
>>> avoids the mythical shock cooling demon or that it lengthens engine
>>> life. My experience is that the engines that are run the hardest
>>> also last the longest. I'm basing this on everything from chainsaws
>>> to lawnmowers
>> to
>>> motorcycles to cars to trucks to off-road heavy equipment (dozers,
>>> skidders, etc.) to airplanes (trainers, air taxi operations, cargo).
>>>
>>> I'm personally not convinced that Lycoming's recommendations
>>> lengthen engine life.
>>>
>>> Matt
>>
>>
>>
>> Shock cooling isn't mythical. It's a fact. It's a physical law.
>
> A physical law, eh? I've had 8 years of engineering school and
> haven't seen this law. Can you provide a reference to the law of
> shock cooling?
> I searched for the "law of shock cooling" in Google and came up
> empty...
>
>
>> Any component subject to heating is subject to this law. If you take
>> a piece of metal and heat it rapidly on one side, that side will
>> expand more rapidly than the other. This gradient of temp will cause
>> a difference in physical size one side to the other. The elastic
>> stress induced by this is cyclically compounded and the resultant
>> locked stress points that build up in the material, particularly if
>> it's a brittle material like cast iron, will eventually fail, given
>> time. The speed at which these stresses are imposed are critical.
>> Speed because if you introduce the heat gradually (decrease the speed
>> of the overall temp change), it's given a chance to get to the other
>> side and expand the other side at a rate not quite so dramatically
>> different as the side the heat is applied to. Simple eh?
>> The quicker you insert heat on one side of the material, the greater
>> the load on the opposite side and the more likely minor damage events
>> (cracks on a near molecular leve) are occuring. These tiny bits of
>> damage will become stress risers for the next time th ematerial is
>> loaded and the cracks will continue to expand until a failure of the
>> component occurs.
>
> Yes, I'm well aware of thermal expansion and its affects. When an
> engine is pulled to idle, the cylinders and heads are getting cooled
> from both sides, the outside via airflow and the inside via airflow
> through the engine. The far greater differential is under full
> throttle during the first take-off when the engine has not yet reached
> thermal equilibrium and you are heating it intensely on the inside and
> cooling it on the outside.
>
> If people wanted to talk about shock heating, then I'd be much more
> willing to believe them and this fits the physics a lot better in my
> opinion. Shock cooling is much less an issue from both a physics
> perspective and an experience perspective.
>

It's the same either way. Cooling and heating are two sides of th esame
coin. It takes time to disapate heat and it's not so much the passage of
heat from one area to another (or the disappation, it's irrelevant) but
the speed at which the cooling or heating is taking place and thus the
gradient across the material.
In short, you take a frozen lump of metal and apply a torch to one side
you have a problem.
Take a cherry red pice of metal and put some ice on side and you have
the same problem (more or less, and disregading crystalisation)


Bertie

On Oct 13, 8:55 pm, Matt Whiting > wrote:

> It seems to me that upon engine start the pistons would heat up much
> faster than the cylinders causing the same net affect as cooling down
> the cylinders faster once hot. Either way the pistons are hotter than
> the cylinders.
>
> Matt

At idle or low power settings there is little heat generated. So
little, in fact, that it can take forever to get the CHT warm enough
to carry out the runup when the temps here are -15 or 20°C. The
cylinder has plenty of time to warm up. It's the sudden removal of the
heat source when the atmosphere is really cold that problems might
arise. In Canada we have to think about it a little more than the
pilot in Arizona. Pistons are aluminum and expand at twice the rate of
the steel cylinders, clearances get small during operational temps,
and shrinking a cylinder quickly around a hot piston is asking for
scuffing or seizure.
We run six Lycs in flight training ops. They usually reach TBO
in good condition. They get a lot of rapid throttle movement, even
though I constantly make noises about not abusing the engines. In my
opinion, opening the throttle too fast can do more damage than closing
it too quickly. Cylinder pressures can get high enough with rapid
throttle movement to cause detonation, however briefly, and cracking
of various parts might occur. A pilot who bangs the throttle open is
applying high manifold pressures to an engine at very low RPM, the
definitive extreme oversquare situation.
Closing it quickly in flight will cause afterfiring (lean
mixtures that often don't fire in the cylinder, igniting instead in
the hot muffler). Cracking of exhaust components is a risk there, and
we find that often enough.
Our students get plenty of forced-approach practice. The engine
is throttled back in two or three or four seconds. Transport Canada
tells us that some practice forced landings (PFLs) end in the real
thing when the carb ices up during the glide. The syllabus calls for
an application of power for a few seconds every 1000' of altitude loss
to clear the engine, but since the exhaust system is cool in the
glide, it can take much more than a few seconds to clear any ice
accretion and the engine might not respond when necessary.
For those lucky ones with injection, carb ice is not a problem,
but most of us are stuck with carbs and need to be thinking, when we
check the weather before the flight, about what the atmosphere is up
to. We wouldn't dive into unknown waters without making sure there
weren't hidden rocks or sharks around, and we shouldn't launch without
knowing the temp and dewpoint spread, right?

Dan

Newps schrieb:

> The engine manufacturers are about the last place I'd look for engine
> management techniques.

Interesting point of view. Please explain.

Newps schrieb:

> Lycoming and Continental offer no science whatsoever to back up their
> recommendations. There are several companies that can show you hard
> scientific data to disprove what the engine manufacturers claim.

Which are those companies and where do I find those data?

Stefan writes:

> Interesting point of view. Please explain.

There is a potential conflict of interest in that an engine that lasts a long
time delays a replacement sale. However, other factors come into play, such
as liability, reputation and customer goodwill, and so on, so it's not clear
that a manufacturer wouldn't provide good advice.

On Oct 14, 6:59 am, Matt Whiting > wrote:

> Yes, I'm well aware of thermal expansion and its affects. When an
> engine is pulled to idle, the cylinders and heads are getting cooled
> from both sides, the outside via airflow and the inside via airflow
> through the engine.

Except that, with the throttle closed, there is almost no
airflow through the engine.

Dan

Stefan,

> Which are those companies and where do I find those data?
>

One is: http://www.gami.com

See:
http://www.gami.com/gamitcmdefault.html
http://www.avweb.com/news/pelican/182544-1.html
http://www.engineteststand.com/
http://www.advancedpilot.com/

--
Thomas Borchert (EDDH)

"Newps" > wrote in message
. ..
> Stefan wrote:
>> Matt Barrow schrieb:
>>
>>> Thomas offers data and evidence, Lycoming offers anecdote and legend.
>>
>> Lycoming offers running engines. Thomas offers words.
>
>
> Lycoming and Continental offer no science whatsoever to back up their
> recommendations. There are several companies that can show you hard
> scientific data to disprove what the engine manufacturers claim.

Somewhere in John Deakins' "Engine Series" articles on AvWeb, there's a
nice graph that Deakins captured from his engine analyzer that duplicates
the conditions that manufacturers' claim to produce "Shock Cooling". It
pretty well debunks the claim. IIRC, he produced both total and immediate
shutdown of the engine as well as gradual power reduction.

IMONSHO, the manufacturers are covering their asses for poor design and
components.
--
Matt Barrow
Performance Homes, LLC.
Cheyenne, WY

Mxsmanic > wrote in
:

> Stefan writes:
>
>> Interesting point of view. Please explain.
>
> There is a potential conflict of interest in that an engine that lasts
> a long time delays a replacement sale. However, other factors come
> into play, such as liability, reputation and customer goodwill, and so
> on, so it's not clear that a manufacturer wouldn't provide good
> advice.
>

You have no idea what you're talking about,

You don't fly and you never will.


Bertie

On Oct 14, 4:13 am, Bertie the Bunyip > wrote:
> Matt Whiting > wrote in news:foeQi.309$2n4.18956
> @news1.epix.net:
>
>
>
>
>
>
>
> > Stefan wrote:
> >> Matt Whiting schrieb:
>
> >>> And Lycoming benefits if your engine lasts fewer hours.
>
> >> So avoiding shock cooling actually lowers its life span? Wow.
>
> > You have no evidence that following Lycoming's recommendations avoids
> > the mythical shock cooling demon or that it lengthens engine life. My
> > experience is that the engines that are run the hardest also last the
> > longest. I'm basing this on everything from chainsaws to lawnmowers
> to
> > motorcycles to cars to trucks to off-road heavy equipment (dozers,
> > skidders, etc.) to airplanes (trainers, air taxi operations, cargo).
>
> > I'm personally not convinced that Lycoming's recommendations lengthen
> > engine life.
>
> > Matt
>
> Shock cooling isn't mythical. It's a fact. It's a physical law.
>
> Any component subject to heating is subject to this law. If you take a
> piece of metal and heat it rapidly on one side, that side will expand
> more rapidly than the other. This gradient of temp will cause a
> difference in physical size one side to the other. The elastic stress
> induced by this is cyclically compounded and the resultant locked stress
> points that build up in the material, particularly if it's a brittle
> material like cast iron, will eventually fail, given time.
> The speed at which these stresses are imposed are critical. Speed
> because if you introduce the heat gradually (decrease the speed of the
> overall temp change), it's given a chance to get to the other side and
> expand the other side at a rate not quite so dramatically different as
> the side the heat is applied to. Simple eh?
> The quicker you insert heat on one side of the material, the greater the
> load on the opposite side and the more likely minor damage events
> (cracks on a near molecular leve) are occuring. These tiny bits of
> damage will become stress risers for the next time th ematerial is
> loaded and the cracks will continue to expand until a failure of the
> component occurs.
>
> I think Lycoming probably figured most of this out in the 1920s,
> Continental even earlier.
>
> However, if it's anectodal evidence that is required...
> I've worked for recip operators where this was a daily problem. In
> glider tugs, for instance, jug failures were common. Operations had to
> be tailered to minimise the strain, and these adopted procedures worked.
> I've also flown big recips and they also required careful management to
> avoid blowing the top of a jug off. The emphasis is always on minimising
> the speed at which th etemps change.
> Jets are no different. Blades ae subject ot enoromous thermal stresses,
> and all of the procedures laid down by the manufacturers are designed to
> extend engine life as much as possible. Everything from engine startup,
> through warmup times to takeoff (admittedly not all manufacturers have
> done this over the years and there are other reasons for this) to
> reduced power for climb to care in reduction of power at top of descent
> are all used to this end.
>
> Other bugbears of the punished engine are micro-seizures and excessive
> friction due to reduced or even sometimes increased, clearances due to
> rapid temp changes.
>
> If the aircraft is being manuevered violently along with rapid power
> changes, you can add precession to the damage being caused.In
> aerobatics, obviously.
> That is why, even though the pilot must be prompt with his power
> changes to maintain control of his speed, it is accepted that it is best
> practice to make these changes as smoothly and deliberately as possible
> whilst still meeting the demands of aircraft control.
> But even relatively mild manuevering combined with rapid throttle
> changes will induce the same stresses to a lesser degree and are
> therefore undesirable.
>
> None of this is new info , of course. I have engine operating manuals
> from the 1930s that address all of these issues and modern manuals
> remain pretty much the same. These principles were understood long
> before that. Interestingly though, I have a workshop manual for a 1933
> Le Blond that talks about corrosion on the inside of a hollow crank,
> it's causes and prevention, all of which could directly apply to that
> debacle with lycomings. Seems some lessons have been forgotten!
> The manufaturers have no interest in misleading anyone into screwing
> their engines up to increase their profits. They rely on their
> reputations as builders of reliable engines to increase their sales.
> An engine that never makes it to TBO would be a liability to them..
> Want to increase your engine life and reliability? Don't bash your
> throttle around.
>
> For real improvement in addition to these suggestions, install a pre-
> oiler and oil heater. Your bottom end will last forever and the top will
> be much improved as well. If you're operating on condition you might get
> double the TBO overall or more! A really good filter is essential for
> longevity as well.Get an STC for one if there's not one readily
> available for your airplane..
>
> Bertie- Hide quoted text -
>
> - Show quoted text -

In this instance I agree with Bertie the Bunyip except for the simple
fact that,,,, If Lycoming and Continental and the FAA knew that a pre-
oiler and and oil heater would extent the life and safety of an
internal combustion engine as much as you claim it will, all of them
would have been made them mandatory 59 years ago. As a former racer I
totally agree to the idea of a pre-oiler and warm oil at start up, to
the idea the bottom end will last " forever", well, good luck on that.
Thank god my aircraft engine is water cooled.. No chance of shock
cooling for me.... As a post note Fall flying here in Jackson Hole Wy.
is spectacular. 27f sittin on the ramp, 18f at altitude, leaf colors,
breathtaking... Snow up high, Almost better then sex..I love the
mountains. !!!!!!!!!!!!!!!!!!!!!!


Ben
www.haaspowerair.com

" > wrote in
ps.com:

> On Oct 14, 4:13 am, Bertie the Bunyip > wrote:
>> Matt Whiting > wrote in news:foeQi.309$2n4.18956
>> @news1.epix.net:
>>
>>
>>
>>
>>
>>
>>
>> > Stefan wrote:
>> >> Matt Whiting schrieb:
>>
>> >>> And Lycoming benefits if your engine lasts fewer hours.
>>
>> >> So avoiding shock cooling actually lowers its life span? Wow.
>>
>> > You have no evidence that following Lycoming's recommendations
avoids
>> > the mythical shock cooling demon or that it lengthens engine life.
My
>> > experience is that the engines that are run the hardest also last
the
>> > longest. I'm basing this on everything from chainsaws to
lawnmowers
>> to
>> > motorcycles to cars to trucks to off-road heavy equipment (dozers,
>> > skidders, etc.) to airplanes (trainers, air taxi operations,
cargo).
>>
>> > I'm personally not convinced that Lycoming's recommendations
lengthen
>> > engine life.
>>
>> > Matt
>>
>> Shock cooling isn't mythical. It's a fact. It's a physical law.
>>
>> Any component subject to heating is subject to this law. If you take
a
>> piece of metal and heat it rapidly on one side, that side will expand
>> more rapidly than the other. This gradient of temp will cause a
>> difference in physical size one side to the other. The elastic stress
>> induced by this is cyclically compounded and the resultant locked
stress
>> points that build up in the material, particularly if it's a brittle
>> material like cast iron, will eventually fail, given time.
>> The speed at which these stresses are imposed are critical. Speed
>> because if you introduce the heat gradually (decrease the speed of
the
>> overall temp change), it's given a chance to get to the other side
and
>> expand the other side at a rate not quite so dramatically different
as
>> the side the heat is applied to. Simple eh?
>> The quicker you insert heat on one side of the material, the greater
the
>> load on the opposite side and the more likely minor damage events
>> (cracks on a near molecular leve) are occuring. These tiny bits of
>> damage will become stress risers for the next time th ematerial is
>> loaded and the cracks will continue to expand until a failure of the
>> component occurs.
>>
>> I think Lycoming probably figured most of this out in the 1920s,
>> Continental even earlier.
>>
>> However, if it's anectodal evidence that is required...
>> I've worked for recip operators where this was a daily problem. In
>> glider tugs, for instance, jug failures were common. Operations had
to
>> be tailered to minimise the strain, and these adopted procedures
worked.
>> I've also flown big recips and they also required careful management
to
>> avoid blowing the top of a jug off. The emphasis is always on
minimising
>> the speed at which th etemps change.
>> Jets are no different. Blades ae subject ot enoromous thermal
stresses,
>> and all of the procedures laid down by the manufacturers are designed
to
>> extend engine life as much as possible. Everything from engine
startup,
>> through warmup times to takeoff (admittedly not all manufacturers
have
>> done this over the years and there are other reasons for this) to
>> reduced power for climb to care in reduction of power at top of
descent
>> are all used to this end.
>>
>> Other bugbears of the punished engine are micro-seizures and
excessive
>> friction due to reduced or even sometimes increased, clearances due
to
>> rapid temp changes.
>>
>> If the aircraft is being manuevered violently along with rapid power
>> changes, you can add precession to the damage being caused.In
>> aerobatics, obviously.
>> That is why, even though the pilot must be prompt with his power
>> changes to maintain control of his speed, it is accepted that it is
best
>> practice to make these changes as smoothly and deliberately as
possible
>> whilst still meeting the demands of aircraft control.
>> But even relatively mild manuevering combined with rapid throttle
>> changes will induce the same stresses to a lesser degree and are
>> therefore undesirable.
>>
>> None of this is new info , of course. I have engine operating manuals
>> from the 1930s that address all of these issues and modern manuals
>> remain pretty much the same. These principles were understood long
>> before that. Interestingly though, I have a workshop manual for a
1933
>> Le Blond that talks about corrosion on the inside of a hollow crank,
>> it's causes and prevention, all of which could directly apply to that
>> debacle with lycomings. Seems some lessons have been forgotten!
>> The manufaturers have no interest in misleading anyone into screwing
>> their engines up to increase their profits. They rely on their
>> reputations as builders of reliable engines to increase their sales.
>> An engine that never makes it to TBO would be a liability to them..
>> Want to increase your engine life and reliability? Don't bash your
>> throttle around.
>>
>> For real improvement in addition to these suggestions, install a pre-
>> oiler and oil heater. Your bottom end will last forever and the top
will
>> be much improved as well. If you're operating on condition you might
get
>> double the TBO overall or more! A really good filter is essential for
>> longevity as well.Get an STC for one if there's not one readily
>> available for your airplane..
>>
>> Bertie- Hide quoted text -
>>
>> - Show quoted text -
>
> In this instance I agree with Bertie the Bunyip except for the simple
> fact that,,,, If Lycoming and Continental and the FAA knew that a pre-
> oiler and and oil heater would extent the life and safety of an
> internal combustion engine as much as you claim it will, all of them
> would have been made them mandatory 59 years ago. As a former racer I
> totally agree to the idea of a pre-oiler and warm oil at start up, to
> the idea the bottom end will last " forever", well, good luck on that.


just a flippant remark. didn't think anyone would take it seriously!


Seriously, though, they will increase engine life considerably.

Bertie

Stefan wrote:
> Newps schrieb:
>
>> The engine manufacturers are about the last place I'd look for engine
>> management techniques.
>
> Interesting point of view. Please explain.


Lean of peak. In the face of overwhelming evidence both engine
manufacturers flat out state that LOP is harmful to your engine.
Continental has slightly relented as they publish some LOP settings for
their 550 engines. But try and engage anyone in that company in
meaningful discourse on LOP ops and you get blank stares. They
absolutely refuse. LOP not only saves gas but is tremendously easier on
the engine.

On Oct 14, 3:22 pm, " > wrote:

> In this instance I agree with Bertie the Bunyip except for the simple
> fact that,,,, If Lycoming and Continental and the FAA knew that a pre-
> oiler and and oil heater would extent the life and safety of an
> internal combustion engine as much as you claim it will, all of them
> would have been made them mandatory 59 years ago.


They could extend the life, but won't make the engine fail-
proof. They add weight and complexity and further fail points.

I have a homebuilt with an old A-65. These old engines and their
brethren (A-75, A-80, C-75, C-85, C-90) all had a reputation for
losing oil pump prime when left sitting for long periods. The oil pump
is machined into the accessory cover and has an aluminum plate bolted
down over it, with minimal clearance over the pump gears. This plate
is supposed to seal tightly against the machined case surface, and I
always used a little sealant on it to discourage the leakage of all
the oil out of it when sitting, but most do leak, even with sealant,
and if the pump is dry enough the pressure won't come up or it'll be
delayed. The crankshaft and its bearings suffer accordingly, and this
spring I had to take mine apart and have the crank ground. The front
rod journal gets it the worst, being narrow, heavily loaded and
farthest from the pump.
I used to do what some other small Continental operators have
to do: take the temp probe out of the filter screen and pump some oil
into the filter, where it would fall into the pump and prime it. It
got so I didn't even bother starting the thing first to see if
pressure would build. Too chancy.
I finally got fed up and machined a little manual preoiler pump
from aluminum, a few fittings, O-rings, small springs and bearing
balls, and installed it. Homebuilts are wonderful that way. Now I open
a small valve, pump the preoiler about 20 strokes, close the valve and
start the engine. The oil pressure comes up instantly. The 20 strokes
fills the entire oil system and primes the pump, too. I expect that
crank to last awhile, now.

Dan

Bertie the Bunyip wrote:
> Matt Whiting > wrote in
> :
>
>> Bertie the Bunyip wrote:
>>> Matt Whiting > wrote in news:foeQi.309$2n4.18956
>>> @news1.epix.net:
>>>
>>>> Stefan wrote:
>>>>> Matt Whiting schrieb:
>>>>>
>>>>>> And Lycoming benefits if your engine lasts fewer hours.
>>>>> So avoiding shock cooling actually lowers its life span? Wow.
>>>> You have no evidence that following Lycoming's recommendations
>>>> avoids the mythical shock cooling demon or that it lengthens engine
>>>> life. My experience is that the engines that are run the hardest
>>>> also last the longest. I'm basing this on everything from chainsaws
>>>> to lawnmowers
>>> to
>>>> motorcycles to cars to trucks to off-road heavy equipment (dozers,
>>>> skidders, etc.) to airplanes (trainers, air taxi operations, cargo).
>>>>
>>>> I'm personally not convinced that Lycoming's recommendations
>>>> lengthen engine life.
>>>>
>>>> Matt
>>>
>>>
>>> Shock cooling isn't mythical. It's a fact. It's a physical law.
>> A physical law, eh? I've had 8 years of engineering school and
>> haven't seen this law. Can you provide a reference to the law of
>> shock cooling?
>> I searched for the "law of shock cooling" in Google and came up
>> empty...
>>
>>
>>> Any component subject to heating is subject to this law. If you take
>>> a piece of metal and heat it rapidly on one side, that side will
>>> expand more rapidly than the other. This gradient of temp will cause
>>> a difference in physical size one side to the other. The elastic
>>> stress induced by this is cyclically compounded and the resultant
>>> locked stress points that build up in the material, particularly if
>>> it's a brittle material like cast iron, will eventually fail, given
>>> time. The speed at which these stresses are imposed are critical.
>>> Speed because if you introduce the heat gradually (decrease the speed
>>> of the overall temp change), it's given a chance to get to the other
>>> side and expand the other side at a rate not quite so dramatically
>>> different as the side the heat is applied to. Simple eh?
>>> The quicker you insert heat on one side of the material, the greater
>>> the load on the opposite side and the more likely minor damage events
>>> (cracks on a near molecular leve) are occuring. These tiny bits of
>>> damage will become stress risers for the next time th ematerial is
>>> loaded and the cracks will continue to expand until a failure of the
>>> component occurs.
>> Yes, I'm well aware of thermal expansion and its affects. When an
>> engine is pulled to idle, the cylinders and heads are getting cooled
>> from both sides, the outside via airflow and the inside via airflow
>> through the engine. The far greater differential is under full
>> throttle during the first take-off when the engine has not yet reached
>> thermal equilibrium and you are heating it intensely on the inside and
>> cooling it on the outside.
>>
>> If people wanted to talk about shock heating, then I'd be much more
>> willing to believe them and this fits the physics a lot better in my
>> opinion. Shock cooling is much less an issue from both a physics
>> perspective and an experience perspective.
>>
>
> It's the same either way. Cooling and heating are two sides of th esame
> coin. It takes time to disapate heat and it's not so much the passage of
> heat from one area to another (or the disappation, it's irrelevant) but
> the speed at which the cooling or heating is taking place and thus the
> gradient across the material.
> In short, you take a frozen lump of metal and apply a torch to one side
> you have a problem.
> Take a cherry red pice of metal and put some ice on side and you have
> the same problem (more or less, and disregading crystalisation)

It is the same if the same delta T is present, but my point is that it
is easier to heat something quickly than cool it quickly. Even at 250
C, you are only 523 degrees above absolute zero. So, this the absolute
largest delta T you can induce for cooling, and it is very hard to get
absolute zero, so you are more likely to have a cool temp closer to 0 C
yielding a delta T of only 250 degrees.

On the hot side things are more open-ended. It isn't too hard to get
450 C exhaust gas temperatures. For an engine that is started at say 20
C ambient temperature, you now have a delta T of 430 degrees which is
much greater than the 250 likely on the cooling side of the cycle.

That is one reason why I suspect that "shock heating" is more likely to
be an issue than "shock cooling." I suspect you can induce a higher
delta T during a full-throttle initial climb than you can during an idle
descent from a cruise power setting.

Matt

wrote:
> On Oct 14, 6:59 am, Matt Whiting > wrote:
>
>> Yes, I'm well aware of thermal expansion and its affects. When an
>> engine is pulled to idle, the cylinders and heads are getting cooled
>> from both sides, the outside via airflow and the inside via airflow
>> through the engine.
>
> Except that, with the throttle closed, there is almost no
> airflow through the engine.
>
> Dan
>

True, but there is some and there is still some fuel going through which
is vaporized and removes heat as well.

Matt

On Oct 14, 3:31 pm, Bertie the Bunyip > wrote:
> " > wrote oups.com:
>
>
>
>
>
>
>
> > On Oct 14, 4:13 am, Bertie the Bunyip > wrote:
> >> Matt Whiting > wrote in news:foeQi.309$2n4.18956
> >> @news1.epix.net:
>
> >> > Stefan wrote:
> >> >> Matt Whiting schrieb:
>
> >> >>> And Lycoming benefits if your engine lasts fewer hours.
>
> >> >> So avoiding shock cooling actually lowers its life span? Wow.
>
> >> > You have no evidence that following Lycoming's recommendations
> avoids
> >> > the mythical shock cooling demon or that it lengthens engine life.
> My
> >> > experience is that the engines that are run the hardest also last
> the
> >> > longest. I'm basing this on everything from chainsaws to
> lawnmowers
> >> to
> >> > motorcycles to cars to trucks to off-road heavy equipment (dozers,
> >> > skidders, etc.) to airplanes (trainers, air taxi operations,
> cargo).
>
> >> > I'm personally not convinced that Lycoming's recommendations
> lengthen
> >> > engine life.
>
> >> > Matt
>
> >> Shock cooling isn't mythical. It's a fact. It's a physical law.
>
> >> Any component subject to heating is subject to this law. If you take
> a
> >> piece of metal and heat it rapidly on one side, that side will expand
> >> more rapidly than the other. This gradient of temp will cause a
> >> difference in physical size one side to the other. The elastic stress
> >> induced by this is cyclically compounded and the resultant locked
> stress
> >> points that build up in the material, particularly if it's a brittle
> >> material like cast iron, will eventually fail, given time.
> >> The speed at which these stresses are imposed are critical. Speed
> >> because if you introduce the heat gradually (decrease the speed of
> the
> >> overall temp change), it's given a chance to get to the other side
> and
> >> expand the other side at a rate not quite so dramatically different
> as
> >> the side the heat is applied to. Simple eh?
> >> The quicker you insert heat on one side of the material, the greater
> the
> >> load on the opposite side and the more likely minor damage events
> >> (cracks on a near molecular leve) are occuring. These tiny bits of
> >> damage will become stress risers for the next time th ematerial is
> >> loaded and the cracks will continue to expand until a failure of the
> >> component occurs.
>
> >> I think Lycoming probably figured most of this out in the 1920s,
> >> Continental even earlier.
>
> >> However, if it's anectodal evidence that is required...
> >> I've worked for recip operators where this was a daily problem. In
> >> glider tugs, for instance, jug failures were common. Operations had
> to
> >> be tailered to minimise the strain, and these adopted procedures
> worked.
> >> I've also flown big recips and they also required careful management
> to
> >> avoid blowing the top of a jug off. The emphasis is always on
> minimising
> >> the speed at which th etemps change.
> >> Jets are no different. Blades ae subject ot enoromous thermal
> stresses,
> >> and all of the procedures laid down by the manufacturers are designed
> to
> >> extend engine life as much as possible. Everything from engine
> startup,
> >> through warmup times to takeoff (admittedly not all manufacturers
> have
> >> done this over the years and there are other reasons for this) to
> >> reduced power for climb to care in reduction of power at top of
> descent
> >> are all used to this end.
>
> >> Other bugbears of the punished engine are micro-seizures and
> excessive
> >> friction due to reduced or even sometimes increased, clearances due
> to
> >> rapid temp changes.
>
> >> If the aircraft is being manuevered violently along with rapid power
> >> changes, you can add precession to the damage being caused.In
> >> aerobatics, obviously.
> >> That is why, even though the pilot must be prompt with his power
> >> changes to maintain control of his speed, it is accepted that it is
> best
> >> practice to make these changes as smoothly and deliberately as
> possible
> >> whilst still meeting the demands of aircraft control.
> >> But even relatively mild manuevering combined with rapid throttle
> >> changes will induce the same stresses to a lesser degree and are
> >> therefore undesirable.
>
> >> None of this is new info , of course. I have engine operating manuals
> >> from the 1930s that address all of these issues and modern manuals
> >> remain pretty much the same. These principles were understood long
> >> before that. Interestingly though, I have a workshop manual for a
> 1933
> >> Le Blond that talks about corrosion on the inside of a hollow crank,
> >> it's causes and prevention, all of which could directly apply to that
> >> debacle with lycomings. Seems some lessons have been forgotten!
> >> The manufaturers have no interest in misleading anyone into screwing
> >> their engines up to increase their profits. They rely on their
> >> reputations as builders of reliable engines to increase their sales.
> >> An engine that never makes it to TBO would be a liability to them..
> >> Want to increase your engine life and reliability? Don't bash your
> >> throttle around.
>
> >> For real improvement in addition to these suggestions, install a pre-
> >> oiler and oil heater. Your bottom end will last forever and the top
> will
> >> be much improved as well. If you're operating on condition you might
> get
> >> double the TBO overall or more! A really good filter is essential for
> >> longevity as well.Get an STC for one if there's not one readily
> >> available for your airplane..
>
> >> Bertie- Hide quoted text -
>
> >> - Show quoted text -
>
> > In this instance I agree with Bertie the Bunyip except for the simple
> > fact that,,,, If Lycoming and Continental and the FAA knew that a pre-
> > oiler and and oil heater would extent the life and safety of an
> > internal combustion engine as much as you claim it will, all of them
> > would have been made them mandatory 59 years ago. As a former racer I
> > totally agree to the idea of a pre-oiler and warm oil at start up, to
> > the idea the bottom end will last " forever", well, good luck on that.
>
> just a flippant remark. didn't think anyone would take it seriously!
>
> Seriously, though, they will increase engine life considerably.
>
> Bertie- Hide quoted text -
>
> - Show quoted text -

I agree 100%..

ya know I am kinda warming up to ol Bertie...

Ben.

Matt Whiting > wrote in
:

> Bertie the Bunyip wrote:
>> Matt Whiting > wrote in
>> :
>>
>>> Bertie the Bunyip wrote:
>>>> Matt Whiting > wrote in news:foeQi.309$2n4.18956
>>>> @news1.epix.net:
>>>>
>>>>> Stefan wrote:
>>>>>> Matt Whiting schrieb:
>>>>>>
>>>>>>> And Lycoming benefits if your engine lasts fewer hours.
>>>>>> So avoiding shock cooling actually lowers its life span? Wow.
>>>>> You have no evidence that following Lycoming's recommendations
>>>>> avoids the mythical shock cooling demon or that it lengthens
>>>>> engine life. My experience is that the engines that are run the
>>>>> hardest also last the longest. I'm basing this on everything from
>>>>> chainsaws to lawnmowers
>>>> to
>>>>> motorcycles to cars to trucks to off-road heavy equipment (dozers,
>>>>> skidders, etc.) to airplanes (trainers, air taxi operations,
>>>>> cargo).
>>>>>
>>>>> I'm personally not convinced that Lycoming's recommendations
>>>>> lengthen engine life.
>>>>>
>>>>> Matt
>>>>
>>>>
>>>> Shock cooling isn't mythical. It's a fact. It's a physical law.
>>> A physical law, eh? I've had 8 years of engineering school and
>>> haven't seen this law. Can you provide a reference to the law of
>>> shock cooling?
>>> I searched for the "law of shock cooling" in Google and came up
>>> empty...
>>>
>>>
>>>> Any component subject to heating is subject to this law. If you
>>>> take a piece of metal and heat it rapidly on one side, that side
>>>> will expand more rapidly than the other. This gradient of temp will
>>>> cause a difference in physical size one side to the other. The
>>>> elastic stress induced by this is cyclically compounded and the
>>>> resultant locked stress points that build up in the material,
>>>> particularly if it's a brittle material like cast iron, will
>>>> eventually fail, given time. The speed at which these stresses are
>>>> imposed are critical. Speed because if you introduce the heat
>>>> gradually (decrease the speed of the overall temp change), it's
>>>> given a chance to get to the other side and expand the other side
>>>> at a rate not quite so dramatically different as the side the heat
>>>> is applied to. Simple eh? The quicker you insert heat on one side
>>>> of the material, the greater the load on the opposite side and the
>>>> more likely minor damage events (cracks on a near molecular leve)
>>>> are occuring. These tiny bits of damage will become stress risers
>>>> for the next time th ematerial is loaded and the cracks will
>>>> continue to expand until a failure of the component occurs.
>>> Yes, I'm well aware of thermal expansion and its affects. When an
>>> engine is pulled to idle, the cylinders and heads are getting cooled
>>> from both sides, the outside via airflow and the inside via airflow
>>> through the engine. The far greater differential is under full
>>> throttle during the first take-off when the engine has not yet
>>> reached thermal equilibrium and you are heating it intensely on the
>>> inside and cooling it on the outside.
>>>
>>> If people wanted to talk about shock heating, then I'd be much more
>>> willing to believe them and this fits the physics a lot better in my
>>> opinion. Shock cooling is much less an issue from both a physics
>>> perspective and an experience perspective.
>>>
>>
>> It's the same either way. Cooling and heating are two sides of th
>> esame coin. It takes time to disapate heat and it's not so much the
>> passage of heat from one area to another (or the disappation, it's
>> irrelevant) but the speed at which the cooling or heating is taking
>> place and thus the gradient across the material.
>> In short, you take a frozen lump of metal and apply a torch to one
>> side you have a problem.
>> Take a cherry red pice of metal and put some ice on side and you have
>> the same problem (more or less, and disregading crystalisation)
>
> It is the same if the same delta T is present, but my point is that it
> is easier to heat something quickly than cool it quickly. Even at 250
> C, you are only 523 degrees above absolute zero. So, this the
> absolute largest delta T you can induce for cooling, and it is very
> hard to get absolute zero, so you are more likely to have a cool temp
> closer to 0 C yielding a delta T of only 250 degrees.
>
> On the hot side things are more open-ended. It isn't too hard to get
> 450 C exhaust gas temperatures. For an engine that is started at say
> 20 C ambient temperature, you now have a delta T of 430 degrees which
> is much greater than the 250 likely on the cooling side of the cycle.
>
> That is one reason why I suspect that "shock heating" is more likely
> to be an issue than "shock cooling." I suspect you can induce a
> higher delta T during a full-throttle initial climb than you can
> during an idle descent from a cruise power setting.
>

Right, I'm with you now. yeah, I can buy that. Froma strictly clinical
viewpoint it absolutely makes sense. My experience with damage says
otherwise, though I can offer no explanation why that should be the
case. Years ago I towed gliders with Bird-dogs and we cracked a lot of
cylinders when we just closed the throttle after release. When we moved
to gradual reduction to ultimately 1500 RPM the problem disappeared
completely. Later, when I flew big pistons,the procedures for cooling
down the cylinders on the way down. You were almost gaurunteed a crack
if you yanked the taps closed. Can't see how we went from cold to hot
any more than you would just starting up and taking off.
I've just bought an aerobatic airplane with a Lycoming. We're not
expecing to get to TBO with the engine because we'll be doing aerobaics
with it, but of course we're prepared to live with that.
I suppose the point I'm making is that even if shick cooling is over-
rated, it certainly does no harm to observe trad practices as if it did.

wrote in news:1192408304.403477.14100
@k35g2000prh.googlegroups.com:

> On Oct 14, 3:22 pm, " > wrote:
>
>> In this instance I agree with Bertie the Bunyip except for the simple
>> fact that,,,, If Lycoming and Continental and the FAA knew that a
pre-
>> oiler and and oil heater would extent the life and safety of an
>> internal combustion engine as much as you claim it will, all of them
>> would have been made them mandatory 59 years ago.
>
>
> They could extend the life, but won't make the engine fail-
> proof. They add weight and complexity and further fail points.
>
> I have a homebuilt with an old A-65. These old engines and their
> brethren (A-75, A-80, C-75, C-85, C-90) all had a reputation for
> losing oil pump prime when left sitting for long periods. The oil pump
> is machined into the accessory cover and has an aluminum plate bolted
> down over it, with minimal clearance over the pump gears. This plate
> is supposed to seal tightly against the machined case surface, and I
> always used a little sealant on it to discourage the leakage of all
> the oil out of it when sitting, but most do leak, even with sealant,
> and if the pump is dry enough the pressure won't come up or it'll be
> delayed. The crankshaft and its bearings suffer accordingly, and this
> spring I had to take mine apart and have the crank ground. The front
> rod journal gets it the worst, being narrow, heavily loaded and
> farthest from the pump.
> I used to do what some other small Continental operators have
> to do: take the temp probe out of the filter screen and pump some oil
> into the filter, where it would fall into the pump and prime it. It
> got so I didn't even bother starting the thing first to see if
> pressure would build. Too chancy.
> I finally got fed up and machined a little manual preoiler pump
> from aluminum, a few fittings, O-rings, small springs and bearing
> balls, and installed it. Homebuilts are wonderful that way. Now I open
> a small valve, pump the preoiler about 20 strokes, close the valve and
> start the engine. The oil pressure comes up instantly. The 20 strokes
> fills the entire oil system and primes the pump, too. I expect that
> crank to last awhile, now.
>

Wow! thought of doing that myself for my own A-65, but I've sold it
now. Do you have drawings for it? I've got a homebuilt. on the move and
it would be a most welcome addition to it!
In fact that sounds like something you should really send in to the
Experimenter or SA


Bertie

" > wrote in
oups.com:

> On Oct 14, 3:31 pm, Bertie the Bunyip > wrote:
>> " > wrote
>> oups.com:
>>
>>
>>
>>
>>
>>
>>
>> > On Oct 14, 4:13 am, Bertie the Bunyip > wrote:
>> >> Matt Whiting > wrote in news:foeQi.309$2n4.18956
>> >> @news1.epix.net:
>>
>> >> > Stefan wrote:
>> >> >> Matt Whiting schrieb:
>>
>> >> >>> And Lycoming benefits if your engine lasts fewer hours.
>>
>> >> >> So avoiding shock cooling actually lowers its life span? Wow.
>>
>> >> > You have no evidence that following Lycoming's recommendations
>> avoids
>> >> > the mythical shock cooling demon or that it lengthens engine
>> >> > life.
>> My
>> >> > experience is that the engines that are run the hardest also
>> >> > last
>> the
>> >> > longest. I'm basing this on everything from chainsaws to
>> lawnmowers
>> >> to
>> >> > motorcycles to cars to trucks to off-road heavy equipment
>> >> > (dozers, skidders, etc.) to airplanes (trainers, air taxi
>> >> > operations,
>> cargo).
>>
>> >> > I'm personally not convinced that Lycoming's recommendations
>> lengthen
>> >> > engine life.
>>
>> >> > Matt
>>
>> >> Shock cooling isn't mythical. It's a fact. It's a physical law.
>>
>> >> Any component subject to heating is subject to this law. If you
>> >> take
>> a
>> >> piece of metal and heat it rapidly on one side, that side will
>> >> expand more rapidly than the other. This gradient of temp will
>> >> cause a difference in physical size one side to the other. The
>> >> elastic stress induced by this is cyclically compounded and the
>> >> resultant locked
>> stress
>> >> points that build up in the material, particularly if it's a
>> >> brittle material like cast iron, will eventually fail, given time.
>> >> The speed at which these stresses are imposed are critical. Speed
>> >> because if you introduce the heat gradually (decrease the speed of
>> the
>> >> overall temp change), it's given a chance to get to the other side
>> and
>> >> expand the other side at a rate not quite so dramatically
>> >> different
>> as
>> >> the side the heat is applied to. Simple eh?
>> >> The quicker you insert heat on one side of the material, the
>> >> greater
>> the
>> >> load on the opposite side and the more likely minor damage events
>> >> (cracks on a near molecular leve) are occuring. These tiny bits of
>> >> damage will become stress risers for the next time th ematerial is
>> >> loaded and the cracks will continue to expand until a failure of
>> >> the component occurs.
>>
>> >> I think Lycoming probably figured most of this out in the 1920s,
>> >> Continental even earlier.
>>
>> >> However, if it's anectodal evidence that is required...
>> >> I've worked for recip operators where this was a daily problem. In
>> >> glider tugs, for instance, jug failures were common. Operations
>> >> had
>> to
>> >> be tailered to minimise the strain, and these adopted procedures
>> worked.
>> >> I've also flown big recips and they also required careful
>> >> management
>> to
>> >> avoid blowing the top of a jug off. The emphasis is always on
>> minimising
>> >> the speed at which th etemps change.
>> >> Jets are no different. Blades ae subject ot enoromous thermal
>> stresses,
>> >> and all of the procedures laid down by the manufacturers are
>> >> designed
>> to
>> >> extend engine life as much as possible. Everything from engine
>> startup,
>> >> through warmup times to takeoff (admittedly not all manufacturers
>> have
>> >> done this over the years and there are other reasons for this) to
>> >> reduced power for climb to care in reduction of power at top of
>> descent
>> >> are all used to this end.
>>
>> >> Other bugbears of the punished engine are micro-seizures and
>> excessive
>> >> friction due to reduced or even sometimes increased, clearances
>> >> due
>> to
>> >> rapid temp changes.
>>
>> >> If the aircraft is being manuevered violently along with rapid
>> >> power changes, you can add precession to the damage being
>> >> caused.In aerobatics, obviously.
>> >> That is why, even though the pilot must be prompt with his power
>> >> changes to maintain control of his speed, it is accepted that it
>> >> is
>> best
>> >> practice to make these changes as smoothly and deliberately as
>> possible
>> >> whilst still meeting the demands of aircraft control.
>> >> But even relatively mild manuevering combined with rapid throttle
>> >> changes will induce the same stresses to a lesser degree and are
>> >> therefore undesirable.
>>
>> >> None of this is new info , of course. I have engine operating
>> >> manuals from the 1930s that address all of these issues and modern
>> >> manuals remain pretty much the same. These principles were
>> >> understood long before that. Interestingly though, I have a
>> >> workshop manual for a
>> 1933
>> >> Le Blond that talks about corrosion on the inside of a hollow
>> >> crank, it's causes and prevention, all of which could directly
>> >> apply to that debacle with lycomings. Seems some lessons have been
>> >> forgotten! The manufaturers have no interest in misleading anyone
>> >> into screwing their engines up to increase their profits. They
>> >> rely on their reputations as builders of reliable engines to
>> >> increase their sales. An engine that never makes it to TBO would
>> >> be a liability to them.. Want to increase your engine life and
>> >> reliability? Don't bash your throttle around.
>>
>> >> For real improvement in addition to these suggestions, install a
>> >> pre- oiler and oil heater. Your bottom end will last forever and
>> >> the top
>> will
>> >> be much improved as well. If you're operating on condition you
>> >> might
>> get
>> >> double the TBO overall or more! A really good filter is essential
>> >> for longevity as well.Get an STC for one if there's not one
>> >> readily available for your airplane..
>>
>> >> Bertie- Hide quoted text -
>>
>> >> - Show quoted text -
>>
>> > In this instance I agree with Bertie the Bunyip except for the
>> > simple fact that,,,, If Lycoming and Continental and the FAA knew
>> > that a pre- oiler and and oil heater would extent the life and
>> > safety of an internal combustion engine as much as you claim it
>> > will, all of them would have been made them mandatory 59 years ago.
>> > As a former racer I totally agree to the idea of a pre-oiler and
>> > warm oil at start up, to the idea the bottom end will last "
>> > forever", well, good luck on that.
>>
>> just a flippant remark. didn't think anyone would take it seriously!
>>
>> Seriously, though, they will increase engine life considerably.
>>
>> Bertie- Hide quoted text -
>>
>> - Show quoted text -
>
> I agree 100%..
>
> ya know I am kinda warming up to ol Bertie...
>


Why wouldn't you? I'm as cuddly as hell.

Bertie

Bertie the Bunyip wrote:
> Matt Whiting > wrote in

>> It is the same if the same delta T is present, but my point is that it
>> is easier to heat something quickly than cool it quickly. Even at 250
>> C, you are only 523 degrees above absolute zero. So, this the
>> absolute largest delta T you can induce for cooling, and it is very
>> hard to get absolute zero, so you are more likely to have a cool temp
>> closer to 0 C yielding a delta T of only 250 degrees.
>>
>> On the hot side things are more open-ended. It isn't too hard to get
>> 450 C exhaust gas temperatures. For an engine that is started at say
>> 20 C ambient temperature, you now have a delta T of 430 degrees which
>> is much greater than the 250 likely on the cooling side of the cycle.
>>
>> That is one reason why I suspect that "shock heating" is more likely
>> to be an issue than "shock cooling." I suspect you can induce a
>> higher delta T during a full-throttle initial climb than you can
>> during an idle descent from a cruise power setting.
>>
>
> Right, I'm with you now. yeah, I can buy that. Froma strictly clinical
> viewpoint it absolutely makes sense. My experience with damage says
> otherwise, though I can offer no explanation why that should be the
> case. Years ago I towed gliders with Bird-dogs and we cracked a lot of
> cylinders when we just closed the throttle after release. When we moved
> to gradual reduction to ultimately 1500 RPM the problem disappeared
> completely. Later, when I flew big pistons,the procedures for cooling
> down the cylinders on the way down. You were almost gaurunteed a crack
> if you yanked the taps closed. Can't see how we went from cold to hot
> any more than you would just starting up and taking off.
> I've just bought an aerobatic airplane with a Lycoming. We're not
> expecing to get to TBO with the engine because we'll be doing aerobaics
> with it, but of course we're prepared to live with that.
> I suppose the point I'm making is that even if shick cooling is over-
> rated, it certainly does no harm to observe trad practices as if it did.

I suspect, as with most "real world" problems, that there is more in
play than delta T induced stress. Probably geometry and other factors.
Maybe having the thin fins on the outside vs. thick metal on the
inside is making a big difference in the stress profile.

I've not had experience with the larger engines or with radials.
However, my experience with O-470 and smaller engines is that shock
cooling just isn't an issue and many folks are paranoid for nothing.

Operating the engine as if shock cooling was an issue is probably not a
problem in most cases, but if it causes you, as it has with Jay, to not
practice essential emergency procedures, then I disagree that it causes
no harm. This may be very harmful should Jay experience an engine
failure for real.

Matt

Matt Whiting > wrote in
:

> Bertie the Bunyip wrote:
>> Matt Whiting > wrote in
>
>>> It is the same if the same delta T is present, but my point is that
>>> it is easier to heat something quickly than cool it quickly. Even
>>> at 250 C, you are only 523 degrees above absolute zero. So, this
>>> the absolute largest delta T you can induce for cooling, and it is
>>> very hard to get absolute zero, so you are more likely to have a
>>> cool temp closer to 0 C yielding a delta T of only 250 degrees.
>>>
>>> On the hot side things are more open-ended. It isn't too hard to
>>> get 450 C exhaust gas temperatures. For an engine that is started
>>> at say 20 C ambient temperature, you now have a delta T of 430
>>> degrees which is much greater than the 250 likely on the cooling
>>> side of the cycle.
>>>
>>> That is one reason why I suspect that "shock heating" is more likely
>>> to be an issue than "shock cooling." I suspect you can induce a
>>> higher delta T during a full-throttle initial climb than you can
>>> during an idle descent from a cruise power setting.
>>>
>>
>> Right, I'm with you now. yeah, I can buy that. Froma strictly
>> clinical viewpoint it absolutely makes sense. My experience with
>> damage says otherwise, though I can offer no explanation why that
>> should be the case. Years ago I towed gliders with Bird-dogs and we
>> cracked a lot of cylinders when we just closed the throttle after
>> release. When we moved to gradual reduction to ultimately 1500 RPM
>> the problem disappeared completely. Later, when I flew big
>> pistons,the procedures for cooling down the cylinders on the way
>> down. You were almost gaurunteed a crack if you yanked the taps
>> closed. Can't see how we went from cold to hot any more than you
>> would just starting up and taking off. I've just bought an aerobatic
>> airplane with a Lycoming. We're not expecing to get to TBO with the
>> engine because we'll be doing aerobaics with it, but of course we're
>> prepared to live with that. I suppose the point I'm making is that
>> even if shick cooling is over- rated, it certainly does no harm to
>> observe trad practices as if it did.
>
> I suspect, as with most "real world" problems, that there is more in
> play than delta T induced stress. Probably geometry and other
> factors.
> Maybe having the thin fins on the outside vs. thick metal on the
> inside is making a big difference in the stress profile.


I think that has more to do with the gradient along the cylinder as the
combustion chamber expands and the gasses cool. There's a lot more heat
produced up top, thus the intricate finning all over the head. In fact,
in the early days , it was improved casting techniques that alowed this
finning which in turn gave large horsepower boosts to the engines back
then. This was particulalry true in the 20s and thirties, but it still a
widely putsued goal today. the better the cooling, the more fire you can
make and the more fire..
I'll still hold to my original thoughts on it, though. I think the
difficulty in getting heat away from some parts as opposed to others
makes the temp gradient across the cylinder walls uneven in spots and
since I consider I've seen the proof of the pudding I can't shake the
habits of a lifetime as easily as al that!

>
> I've not had experience with the larger engines or with radials.
> However, my experience with O-470 and smaller engines is that shock
> cooling just isn't an issue and many folks are paranoid for nothing.

I'm not paranoid about it, I just don;t think it;s a myth.
>
> Operating the engine as if shock cooling was an issue is probably not
> a problem in most cases, but if it causes you, as it has with Jay, to
> not practice essential emergency procedures, then I disagree that it
> causes no harm. This may be very harmful should Jay experience an
> engine failure for real.
>


I agree and I don't subscribe to that stance in any way shape or form. I
was only picking a nit about shick cooling being a myth.
You have to do what you have to do in an airplane. You have to have some
respect for the engine, but you don;t have to go nuts!
UI mentioned earlier a place I worked did ab initio training in a J-3
(BTW, with no radios, starter or intercom) and, as you might imagine the
engine was up and down a lot.
Standard practice in airplanes like that is to chop the power on
downwind opposite the touchdown point and regualte your approach by
varying the size of your pattern from that point. Now, with some regard
towards rapid cooling we reduced to about 1200 rpm initially and then
chopped it a bit later.
Needless to say the students had very little trouble doing forced
landings when it came to that time in their training.
I've also taught just the same in Cherokees and Cessnas, although
teaching relatively recently within flying clubs I've had to go with the
flow because somewhere some asshole back in the '70s got it in his head
that since airliners do power stabilised approaches it;s a good idea in
a lightplane as well. "Makes the whole trianing experience more
professional" you know.
Now there's a new thread!


Oh, and the J-3? Last time I saw it it had over 4,000 hours on the
engine and hadn;t even had a top.
I think it;s stil flying, though hopefuly it's had a bit of work since
then. Poor old thing!


Bertie

> Oh, and the J-3? Last time I saw it it had over 4,000 hours on the
> engine and hadn;t even had a top.

Those things run forever. Of course, they've got no compression or
power to begin with, so you won't notice any further loss...

;-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay Honeck > wrote in news:1192454721.367225.108920
@i13g2000prf.googlegroups.com:

>> Oh, and the J-3? Last time I saw it it had over 4,000 hours on the
>> engine and hadn;t even had a top.
>
> Those things run forever. Of course, they've got no compression or
> power to begin with, so you won't notice any further loss...
>
> ;-)

There wasn't any further loss. I did the compression checks on it myself
sometimes, and they were still in the 70s then. We rented it out and we
couldn;t have done that if it wasn't sound.
the rest of the airplane, however, was a bit of a mess!
Still it held together the whole time I flew it. Mostly.

Bertie

Bertie the Bunyip > wrote:
>You have to do what you have to do in an airplane. You have to
>have some respect for the engine, but you don;t have to go nuts!
>UI mentioned earlier a place I worked did ab initio training in a J-3
>(BTW, with no radios, starter or intercom) and, as you might
>imagine the engine was up and down a lot. Standard practice in
>airplanes like that is to chop the power on downwind opposite the
>touchdown point and regualte your approach by varying the size
>of your pattern from that point. Now, with some regard towards
>rapid cooling we reduced to about 1200 rpm initially and then
>chopped it a bit later. Needless to say the students had very little
>trouble doing forced landings when it came to that time in their
>training.

That's the method my CFI used.

>I've also taught just the same in Cherokees and Cessnas, although
>teaching relatively recently within flying clubs I've had to go with
>the flow because somewhere some asshole back in the '70s got
>it in his head that since airliners do power stabilised approaches
>it;s a good idea in a lightplane as well. "Makes the whole trianing
>experience more professional" you know.
> Now there's a new thread!

I'll bite (re the new thread)...

In an accident here last year, two pilots (CFI and a student) flying an
A-36 from a local airline-pilot factory came over the fence at around
120 and bounced after their initial touchdown. The CFI finally attempted
to take control (too late) without announcing the exchange of controls
while the student applied power (presumably for a go-round). The plane
veered off the runway at high speed, across the ramp, miraculously
missed tied-down planes in the first couple of rows and then slammed
into a V-tail Bo tied-down on the ramp, completely cutting it up w/the
prop, ripping the chains out of the ground, pushing it into the middle
of the rows, and destroying it. The two pilots were shaken but fine, and
the A-36 had substantial damage but nothing like the V-tail.

After the accident, their excessive over-the-fence speed was discussed,
and it was said that the school does not teach airspeeds during
approaches -- since the students are largely airline-bound individuals,
they teach "descent-rate". Much discussion ensued in the following weeks
about teaching the proper approach *for the airplane you're in at the
time* vs teaching airliner approaches in small, single-engine aircraft.

Your comment caused me to do some Googling. This had some in interesting
stats for a limited accident database.

archive.aya.org/safety/levyhibbler200207.pdf

On Oct 15, 6:20 am, Bertie the Bunyip > wrote:

> Standard practice in airplanes like that is to chop the power on
> downwind opposite the touchdown point and regualte your approach by
> varying the size of your pattern from that point. Now, with some regard
> towards rapid cooling we reduced to about 1200 rpm initially and then
> chopped it a bit later.
> Needless to say the students had very little trouble doing forced
> landings when it came to that time in their training.
> I've also taught just the same in Cherokees and Cessnas, although
> teaching relatively recently within flying clubs I've had to go with the
> flow because somewhere some asshole back in the '70s got it in his head
> that since airliners do power stabilised approaches it;s a good idea in
> a lightplane as well. "Makes the whole trianing experience more
> professional" you know.
> Now there's a new thread!

That's what I was taught in the early '70s when I got my PPL.
When I went for the CPL in the '90s the whole syllabus had changed,
and so had the forced-approach proficiencies of the students and PPLs.
In the instructor refresher courses the forced approach comes up as
the most frequently failed item on both private and commercial flight
tests. The students simply don't know how to adjust glidepath using
nothing more than airspeed, with a slip thrown in if necessary. They
don't get the idea that they can glide farther if they drop the nose
and maintain best glide, drop it farther and go faster if they're
bucking a headwind, pull the nose up and sink if they're high, or get
into ground effect and skim along to the touchdown point if they're a
little short. If no fences are in the way, of course. I once did that
on an instructor checkride and the examiner told me that this was
acceptable. Your mileage may vary.

As far as the preoiler, I made no drawings. I was always an
eyeball engineer, with a basic preliminary sketch if necessary. I made
my living designing, building, rebuilding and inventing stuff for 12
years and this comes easily enough. Maybe, when I get back from a trip
to Africa for the next three weeks, I'll draw something up and submit
it.

Dan

Bertie:
> >> Oh, and the J-3? Last time I saw it it had over 4,000 hours on the
> >> engine and hadn;t even had a top.

Jay:
> > Those things run forever. Of course, they've got no compression or
> > power to begin with, so you won't notice any further loss...
> >
> > ;-)

Bertie:
> There wasn't any further loss. I did the compression checks on it myself
> sometimes, and they were still in the 70s then. We rented it out and we
> couldn;t have done that if it wasn't sound.
> the rest of the airplane, however, was a bit of a mess!
> Still it held together the whole time I flew it. Mostly.

How does that work with regard to the 100-hr and annual inspections for
a rental aircraft? When I worked at the flight school, our mechanics
said you can run an engine past TBO, but they won't sign off an annual
or 100-hr beyond the manufacturer's published TBO. Is signing it off
after TBO not a direct violation of mechanic regs but just a matter of
finding a mechanic willing to take the risk (ours wouldn't do it)?

Shirl > wrote in news:Xmnushal8y-
:

>
> I'll bite (re the new thread)...
>
> In an accident here last year, two pilots (CFI and a student) flying
an
> A-36 from a local airline-pilot factory came over the fence at around
> 120 and bounced after their initial touchdown. The CFI finally
attempted
> to take control (too late) without announcing the exchange of controls
> while the student applied power (presumably for a go-round). The plane
> veered off the runway at high speed, across the ramp, miraculously
> missed tied-down planes in the first couple of rows and then slammed
> into a V-tail Bo tied-down on the ramp, completely cutting it up w/the
> prop, ripping the chains out of the ground, pushing it into the middle
> of the rows, and destroying it. The two pilots were shaken but fine,
and
> the A-36 had substantial damage but nothing like the V-tail.
>
> After the accident, their excessive over-the-fence speed was
discussed,
> and it was said that the school does not teach airspeeds during
> approaches -- since the students are largely airline-bound
individuals,
> they teach "descent-rate". Much discussion ensued in the following
weeks
> about teaching the proper approach *for the airplane you're in at the
> time* vs teaching airliner approaches in small, single-engine
aircraft.
>
> Your comment caused me to do some Googling. This had some in
interesting
> stats for a limited accident database.
>
> archive.aya.org/safety/levyhibbler200207.pdf


Thank you!
And kudos to your instructor.

This is exactly the sort of crap I'm talking about. I fly lightplanes
and I also fly jets. I've flown five of your more poplualr sorts of jets
weighing anything up to 350,000 lbs.
they fly just like airplanes. The only tow things that are even half
true are the neccesisty for stabilised approaches, and even then you can
fudge it a bit, and the "kck it straight n a crosswind " thing. Which is
only the case for some airplanes and even then is widely misunderstood.
In the former instance, the main reason we get stabilised is because in
big swept wing airplanes, it can be hard to control the speed and rate
of descent fo ra couple of reasons. One, the swept wing has a very flat
drag curve, and two, the engines are sometimes slow to spool up (not so
much wiht newer engines) however, you can still do practice deadstick
landings all day in them if you want. They will do them, no problem. We
don't, though. however, n a light single, I think it's a very good idea
to at least keep it on the high side if nothing else and even better,
leave the final a deadstick every time. And yes, I've fown Bonanzas,
Commanches, all sorts. They are all better off doing approaches like
this, at least once you pass below the altitude where all other options
are closed off to you.
Even in light twins, guys tend to drag them in over the fence if the
field is anyways short. Completely unneccesary and very poor technique..

The "they don't put a wing down in a crosswind" thing is complete crap.
There are several jets you have to land wings level (and th ercoupe, of
course, shudder! ) and they are most of th efour engine thingies, the
727 and DC-9/MD80s
( very low wing and outboard flaps) and a couple of other for various
ground contact reasons.
However, corrct technique for this entails crossing the controls as you
would as if you had just done a slip to touchdown and maintaining it
though the landing roll. It feels awful when you do it first, but you
get the hang of it. If you land some of the long ones, like the 727 in a
max crosswind and the runway is narrow, you are acually out over the
edge of the runway as you touch down! You have to squeeze the nose
straight while it is still in the air whilst adding oppistie aileron.
Feels funny but works.
Everything else I've flown lands much better with a wing down and the
fuselage tracking straight down the runway. No question about it. In
fact the autoplit will cross the controls from about 300 feet down when
you're autolanding in most of them nowadays.


End rant.

Shirl > wrote in
:

> Bertie:
>> >> Oh, and the J-3? Last time I saw it it had over 4,000 hours on the
>> >> engine and hadn;t even had a top.
>
> Jay:
>> > Those things run forever. Of course, they've got no compression or
>> > power to begin with, so you won't notice any further loss...
>> >
>> > ;-)
>
> Bertie:
>> There wasn't any further loss. I did the compression checks on it
>> myself sometimes, and they were still in the 70s then. We rented it
>> out and we couldn;t have done that if it wasn't sound.
>> the rest of the airplane, however, was a bit of a mess!
>> Still it held together the whole time I flew it. Mostly.
>
> How does that work with regard to the 100-hr and annual inspections
> for a rental aircraft? When I worked at the flight school, our
> mechanics said you can run an engine past TBO, but they won't sign off
> an annual or 100-hr beyond the manufacturer's published TBO. Is
> signing it off after TBO not a direct violation of mechanic regs but
> just a matter of finding a mechanic willing to take the risk (ours
> wouldn't do it)?
>


Dunno nowadays. but then it was legal. I think it probably still is.
Our operation, though commercial, was part 91 and I'm not aware of any
changes in that rule.
Nowadays I'm only ever involved with club activity and that strictly on
condition. I'd tear down an antique engine every now and again myself,
though.They're too valuable to put a leg out of bed on.

Someone here will know for sure, though.

Interestingly, if you wanted to goto the boundaries of what's legal
commercailly, and someone will certainly correct me if I'm wrong, but
you could still buy an old OX-5, get a set of drawings and a dataplate
for something like a Waco9 or Alexander Eaglerock, build it, certify it
and then operate it out of a cow pasture with your commercial licence,
all legally. #

Oh yeah, no radio.

And why not?
If the operator knew what he was doing why not indeed?

Mind you , I'd get the OX-5 millerised first.


Bertie

wrote in news:1192457661.189109.80330
@e34g2000pro.googlegroups.com:

> On Oct 15, 6:20 am, Bertie the Bunyip > wrote:
>
>> Standard practice in airplanes like that is to chop the power on
>> downwind opposite the touchdown point and regualte your approach by
>> varying the size of your pattern from that point. Now, with some
regard
>> towards rapid cooling we reduced to about 1200 rpm initially and then
>> chopped it a bit later.
>> Needless to say the students had very little trouble doing forced
>> landings when it came to that time in their training.
>> I've also taught just the same in Cherokees and Cessnas, although
>> teaching relatively recently within flying clubs I've had to go with
the
>> flow because somewhere some asshole back in the '70s got it in his
head
>> that since airliners do power stabilised approaches it;s a good idea
in
>> a lightplane as well. "Makes the whole trianing experience more
>> professional" you know.
>> Now there's a new thread!
>
> That's what I was taught in the early '70s when I got my PPL.
> When I went for the CPL in the '90s the whole syllabus had changed,
> and so had the forced-approach proficiencies of the students and PPLs.
> In the instructor refresher courses the forced approach comes up as
> the most frequently failed item on both private and commercial flight
> tests. The students simply don't know how to adjust glidepath using
> nothing more than airspeed, with a slip thrown in if necessary. They
> don't get the idea that they can glide farther if they drop the nose
> and maintain best glide, drop it farther and go faster if they're
> bucking a headwind, pull the nose up and sink if they're high, or get
> into ground effect and skim along to the touchdown point if they're a
> little short. If no fences are in the way, of course. I once did that
> on an instructor checkride and the examiner told me that this was
> acceptable. Your mileage may vary.
>

Sounds OK to me!
I ad the privelage of siting in the back of a cherokee while a guy ws
getting a currenc check recently. The instructor (also a desgnated
examiner) gave him a forced landing into a disused airfield. He didn't
do too good a job of it in the first try, so some instruction ensued.

The examiner wouldn't allow him to slip because he reckons they are
dangerous with the flaps out and that he should wiggle the ailerons back
and forth to lose height. He didn't even want him to slip clean.

Jesus wept.


This examiner had had a fright in a 172 (this was an archer anyway) and
did not alow anyone to slip with flaps out.
While I am firmly in the camp that says some cessnas can get a litle
fuzzy in pitch with full flaps, this is just stupidity incarnate.

> As far as the preoiler, I made no drawings. I was always an
> eyeball engineer, with a basic preliminary sketch if necessary. I made
> my living designing, building, rebuilding and inventing stuff for 12
> years and this comes easily enough. Maybe, when I get back from a trip
> to Africa for the next three weeks, I'll draw something up and submit
> it.
>

Good man!
I'll make one if you do!

Bertie>

Shirl wrote:
>
>In an accident here last year, two pilots (CFI and a student) flying an
>A-36 from a local airline-pilot factory came over the fence at around
>120 and bounced after their initial touchdown. The CFI finally attempted
>to take control (too late) without announcing the exchange of controls
>while the student applied power (presumably for a go-round).

Hey Shirl,

You must be at KCHD. I remember that accident. It missed my plane by
about 100 yds. and missed a buddy's Warrior by just a few feet. The 300
yds. of skid marks (off the runway, through the grass, over the taxiway,
through the grass and then across nearly 100 yds. of ramp) were most
impressive. I wouldn't have believed it if I hadn't seen it with my own eyes.


John Galban=====>N4BQ (PA28-180)

--
Message posted via http://www.aviationkb.com

Shirl:
> >In an accident here last year, two pilots (CFI and a student) flying an
> >A-36 from a local airline-pilot factory came over the fence at around
> >120 and bounced after their initial touchdown. The CFI finally attempted
> >to take control (too late) without announcing the exchange of controls
> >while the student applied power (presumably for a go-round).

"JGalban via AviationKB.com" <u32749@uwe> wrote:
> You must be at KCHD. I remember that accident. It missed my plane by
> about 100 yds. and missed a buddy's Warrior by just a few feet. The 300
> yds. of skid marks (off the runway, through the grass, over the taxiway,
> through the grass and then across nearly 100 yds. of ramp) were most
> impressive. I wouldn't have believed it if I hadn't seen it with my own eyes.

Yes, John, I'm at KCHD. And yes, it was impressive and surprising how
they missed so many other planes in very close proximity. The poor Bo
that was destroyed is still parked there, even after the ramp has been
repaved! We've wondered what's up with that? no insurance?

"Bertie the Bunyip" > wrote

> Seriously, though, they will increase engine life considerably.

'Specially for the guy that is only flying his plane 50 or 100 hours per
year.
--
Jim in NC

Shirl wrote:
>.
>
> The poor Bo
>that was destroyed is still parked there, even after the ramp has been
>repaved! We've wondered what's up with that? no insurance?

I spoke with the owners when I helped them move the wreckage around during
the repaving (that was interesting!). Apparently, they are not happy with
the settlement being offered by the school's insurance company, so they're
holding out and considering suing. Until it's all settled, they have to
keep the wreckage.

John Galban=====>N4BQ (PA28-180)

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums.aspx/aviation/200710/1

Matt: At least in my experience shock cooling did exist. I flew sky divers
in a Skylane and had taken over after another pilot who would climb hard and
chop the throttle and descend to the ground. There were frequent low hour
Top Over hauls, and cracked cylinders. When I began flying the bird the
owner asked me to be aware of cooling it down to fast. My method was to
climb to the drop and then close the cowl flaps, carry 15" MP and spiral
tightly down. It stopped the low hour top overhauls.
My descent rate could be pretty high and the engine was kept relatively
warm.

Stu Fields
Experimental Helo Magazine.
"Matt Whiting" > wrote in message
...
> Bertie the Bunyip wrote:
>> Matt Whiting > wrote in
>
>>> It is the same if the same delta T is present, but my point is that it
>>> is easier to heat something quickly than cool it quickly. Even at 250
>>> C, you are only 523 degrees above absolute zero. So, this the
>>> absolute largest delta T you can induce for cooling, and it is very
>>> hard to get absolute zero, so you are more likely to have a cool temp
>>> closer to 0 C yielding a delta T of only 250 degrees.
>>>
>>> On the hot side things are more open-ended. It isn't too hard to get
>>> 450 C exhaust gas temperatures. For an engine that is started at say
>>> 20 C ambient temperature, you now have a delta T of 430 degrees which
>>> is much greater than the 250 likely on the cooling side of the cycle.
>>>
>>> That is one reason why I suspect that "shock heating" is more likely
>>> to be an issue than "shock cooling." I suspect you can induce a
>>> higher delta T during a full-throttle initial climb than you can
>>> during an idle descent from a cruise power setting.
>>>
>>
>> Right, I'm with you now. yeah, I can buy that. Froma strictly clinical
>> viewpoint it absolutely makes sense. My experience with damage says
>> otherwise, though I can offer no explanation why that should be the case.
>> Years ago I towed gliders with Bird-dogs and we cracked a lot of
>> cylinders when we just closed the throttle after release. When we moved
>> to gradual reduction to ultimately 1500 RPM the problem disappeared
>> completely. Later, when I flew big pistons,the procedures for cooling
>> down the cylinders on the way down. You were almost gaurunteed a crack if
>> you yanked the taps closed. Can't see how we went from cold to hot any
>> more than you would just starting up and taking off. I've just bought an
>> aerobatic airplane with a Lycoming. We're not expecing to get to TBO with
>> the engine because we'll be doing aerobaics with it, but of course we're
>> prepared to live with that.
>> I suppose the point I'm making is that even if shick cooling is over-
>> rated, it certainly does no harm to observe trad practices as if it did.
>
> I suspect, as with most "real world" problems, that there is more in play
> than delta T induced stress. Probably geometry and other factors. Maybe
> having the thin fins on the outside vs. thick metal on the inside is
> making a big difference in the stress profile.
>
> I've not had experience with the larger engines or with radials. However,
> my experience with O-470 and smaller engines is that shock cooling just
> isn't an issue and many folks are paranoid for nothing.
>
> Operating the engine as if shock cooling was an issue is probably not a
> problem in most cases, but if it causes you, as it has with Jay, to not
> practice essential emergency procedures, then I disagree that it causes no
> harm. This may be very harmful should Jay experience an engine failure
> for real.
>
> Matt

"JGalban via AviationKB.com" <u32749@uwe> wrote:
> I spoke with the owners when I helped them move the wreckage
> around during the repaving (that was interesting!). Apparently,
> they are not happy with the settlement being offered by the
> school's insurance company, so they're holding out and
> considering suing. Until it's all settled, they have to keep the
> wreckage.

What a nightmare! I was not aware that plane was with a school. Which
school was it, do you know? Oh well, everyone stops there to look at it!
;-)

On Oct 15, 8:49 am, Bertie the Bunyip > wrote:
>
> The examiner wouldn't allow him to slip because he reckons they are
> dangerous with the flaps out and that he should wiggle the ailerons back
> and forth to lose height. He didn't even want him to slip clean.
>
> Jesus wept.
>
> This examiner had had a fright in a 172 (this was an archer anyway) and
> did not alow anyone to slip with flaps out.
> While I am firmly in the camp that says some cessnas can get a litle
> fuzzy in pitch with full flaps, this is just stupidity incarnate.

Shoot. We do slips with full flaps all the time in 172s, have
done so for years, and never had a scare. I wonder if that "Avoid
Slips With Flaps Extended" applied to some earlier models? I'll have
to check the TCDS sometime.

Dan

In article . com>,
wrote:

> On Oct 15, 8:49 am, Bertie the Bunyip > wrote:
> >
> > The examiner wouldn't allow him to slip because he reckons they are
> > dangerous with the flaps out and that he should wiggle the ailerons back
> > and forth to lose height. He didn't even want him to slip clean.
> >
> > Jesus wept.
> >
> > This examiner had had a fright in a 172 (this was an archer anyway) and
> > did not alow anyone to slip with flaps out.
> > While I am firmly in the camp that says some cessnas can get a litle
> > fuzzy in pitch with full flaps, this is just stupidity incarnate.
>
> Shoot. We do slips with full flaps all the time in 172s, have
> done so for years, and never had a scare. I wonder if that "Avoid
> Slips With Flaps Extended" applied to some earlier models? I'll have
> to check the TCDS sometime.

It affected at least some 172s.

Back when dinosaurs still roamed the taxiways...well, around 1971, a
couple of the instructors who worked for the FBO for which I was a very
lowly minion were wondering why the sole 172 was placarded against slips
with full flaps. (We operated mostly Pipers, various Cherokees and a
Navajo, and this one slightly elderly 172, I don't recall which year it
was.)

So they went out one morning, got plenty of cushion between themselves
and the ground, set the 172 into a landing configuration with full
flaps, and slipped it.

It shook a bit and then went inverted on them. They recovered and came
back home.

It may have only done that in some specific CG configurations, but they
were satisfied, and didn't wonder any longer.

Didn't do it again, either.

wrote in news:1192492570.300275.289550
@i38g2000prf.googlegroups.com:

> On Oct 15, 8:49 am, Bertie the Bunyip > wrote:
>>
>> The examiner wouldn't allow him to slip because he reckons they are
>> dangerous with the flaps out and that he should wiggle the ailerons back
>> and forth to lose height. He didn't even want him to slip clean.
>>
>> Jesus wept.
>>
>> This examiner had had a fright in a 172 (this was an archer anyway) and
>> did not alow anyone to slip with flaps out.
>> While I am firmly in the camp that says some cessnas can get a litle
>> fuzzy in pitch with full flaps, this is just stupidity incarnate.
>
> Shoot. We do slips with full flaps all the time in 172s, have
> done so for years, and never had a scare. I wonder if that "Avoid
> Slips With Flaps Extended" applied to some earlier models? I'll have
> to check the TCDS sometime.
>
> Dan
>
>

Dunno. the manual in a 172 makes reference to a possibility of degraded
elevator control, but I think it's only a bit of a nod, really.
The Bird dog suffers from this ailment big time, though. it has,
essentially, the 172's wing, but the flaps go to 60 degrees. I can tell you
first hand that blanking of both the rudder and elevator are a very real
characteristic of that airplane if you slip it ith full flaps. I did it
once close to the ground and never even thought about it again..

Ernest Christley > wrote in news:47142123$0$32479
:

> Bertie the Bunyip wrote:
>
>>>> It's the same either way. Cooling and heating are two sides of th
>>>> esame coin. It takes time to disapate heat and it's not so much the
>>>> passage of heat from one area to another (or the disappation, it's
>>>> irrelevant) but the speed at which the cooling or heating is taking
>>>> place and thus the gradient across the material.
>>>> In short, you take a frozen lump of metal and apply a torch to one
>>>> side you have a problem.
>>>> Take a cherry red pice of metal and put some ice on side and you have
>>>> the same problem (more or less, and disregading crystalisation)
>>> It is the same if the same delta T is present, but my point is that it
>>> is easier to heat something quickly than cool it quickly. Even at 250
>>> C, you are only 523 degrees above absolute zero. So, this the
>>> absolute largest delta T you can induce for cooling, and it is very
>>> hard to get absolute zero, so you are more likely to have a cool temp
>>> closer to 0 C yielding a delta T of only 250 degrees.
>>>
>>> On the hot side things are more open-ended. It isn't too hard to get
>>> 450 C exhaust gas temperatures. For an engine that is started at say
>>> 20 C ambient temperature, you now have a delta T of 430 degrees which
>>> is much greater than the 250 likely on the cooling side of the cycle.
>>>
>
> With the heating, you only have the few hundred CFM of air passing
> through the engine to heat it. With the cooling, you have all of the
> great outdoors to do the trick. To tie it into your anology, you have a
> butane lighter to heat the metal, and the Atlantic Ocean to cool it.
>

Kind of besides th point. you coudl say the same thing about an oxy
acetylene setup and we all know what that will do to a bit of metal.


Bertie

"Morgans" > wrote in news:LdUQi.347$SQ2.280
@newsfe12.lga:

>
> "Bertie the Bunyip" > wrote
>
>> Seriously, though, they will increase engine life considerably.
>
> 'Specially for the guy that is only flying his plane 50 or 100 hours per
> year.

Yes, absolutely.

Bertie

On Oct 16, 12:43 am, Bertie the Bunyip > wrote:
> wrote in news:1192492570.300275.289550
> @i38g2000prf.googlegroups.com:
>
>
>
> > On Oct 15, 8:49 am, Bertie the Bunyip > wrote:
>
> >> The examiner wouldn't allow him to slip because he reckons they are
> >> dangerous with the flaps out and that he should wiggle the ailerons back
> >> and forth to lose height. He didn't even want him to slip clean.
>
> >> Jesus wept.
>
> >> This examiner had had a fright in a 172 (this was an archer anyway) and
> >> did not alow anyone to slip with flaps out.
> >> While I am firmly in the camp that says some cessnas can get a litle
> >> fuzzy in pitch with full flaps, this is just stupidity incarnate.
>
> > Shoot. We do slips with full flaps all the time in 172s, have
> > done so for years, and never had a scare. I wonder if that "Avoid
> > Slips With Flaps Extended" applied to some earlier models? I'll have
> > to check the TCDS sometime.
>
> > Dan
>
> Dunno. the manual in a 172 makes reference to a possibility of degraded
> elevator control, but I think it's only a bit of a nod, really.
> The Bird dog suffers from this ailment big time, though. it has,
> essentially, the 172's wing, but the flaps go to 60 degrees. I can tell you
> first hand that blanking of both the rudder and elevator are a very real
> characteristic of that airplane if you slip it ith full flaps. I did it
> once close to the ground and never even thought about it again..

Here's what the Type Certificate Data Sheet says:
.................................................. ...................................

D. On flap handle, Models 172 through 172E

(1) "Flaps - Pull to extend
Takeoff Retract 0°
1st notch 10°
Landing 0° - 40°

(2) "Avoid slips with flaps down."

E. Near flap indicator Models 172F (electric flaps) through 17271034,
excluding 17270050)

"Avoid slips with flaps extended."
.................................................. .........................................

The applicable models, 172 through 172F, were built between
1956 and 1964 ('65 model?). There's no mention of the slip with flaps
thing for later models. I wonder if the addition of the back window
changed the airflow enough to keep the elevator flying?

Dan

Souns about right. The Bird dog's reaction was anything but mild, but with
60 degrees of flap it's not surprising really. Teh 172 this DE claims to
have had problems with was a relatively late one, but I could have been
anything that caused it. Some turbulence or maybe his mimagination coupled
with the horrow stories about it.

Seems if one must use full flaps AND slip in landing, I would say the
approach was an abortion that lived. I prefer slips to flaps as you can
instantly remove a slip but the same can't be said for flaps...

Just MY personal opinion...not trying to slam anybody.

Scott


Bob Moore wrote:
> Bertie the Bunyip wrote
>
>>This examiner had had a fright in a 172 and
>>did not alow anyone to slip with flaps out.
>>While I am firmly in the camp that says some
>>cessnas can get a litle fuzzy in pitch with
>>full flaps, this is just stupidity incarnate.
>
>
> About once-a-year I post the following excerpt from "Cessna, Wings for
> the World", a book by William D. Thompson.
>
> Bill Thompson is an Aeronautical engineer from Purdue University and
> worked for Cessna Aircraft Company for 28 years as an engineering test
> pilot and later as the Manager of Flight Test & Aerodynamics.
>
> -------------------------------------------------------------------
> "With the advent of the large slotted flaps in the C-170, C-180, and C-
> 172 we encountered a nose down pitch in forward slips with the wing
> flaps deflected. In some cases it was severe enough to lift the pilot
> against his seat belt if he was slow in checking the motion. For this
> reason a caution note was placed in most of the owner's manuals under
> "Landings" reading "Slips should be avoided with flap settings greater
> than 30° due to a downward pitch encountered under certain combinations
> of airspeed, side-slip angle, and center of gravity loadings". Since
> wing-low drift correction in cross-wind landings is normally performed
> with a minimum flap setting (for better rudder control) this limitation
> did not apply to that maneuver. The cause of the pitching motion is the
> transition of a strong wing downwash over the tail in straight flight to
> a lessened downwash angle over part of the horizontal tail caused by the
> influence of a relative "upwash increment" from the upturned aileron in
> slipping flight. Although not stated in the owner's manuals, we
> privately encouraged flight instructors to explore these effects at high
> altitude, and to pass on the information to their students. This
> phenomenon was elusive and sometimes hard to duplicate, but it was
> thought that a pilot should be aware of its existence and know how to
> counter-act it if it occurs close to the ground.
> When the larger dorsal fin was adopted in the 1972 C-172L, this side-
> slip pitch phenomenon was eliminated, but the cautionary placard was
> retained. In the higher-powered C-172P and C-R172 the placard was
> applicable to a mild pitch "pumping" motion resulting from flap
> outboard-end vortex impingement on the horizontal tail at some
> combinations of side-slip angle, power, and airspeed."
> --------------------------------------------------------------------
> 1959 C-172
> Notice that this prohibition appears in Section III, Operating Details
> of the C-172Owner's Manual and NOT in Section IV, Operating Limitations.
> It is NOT an FAA limitation. Sounds more like "Lawyer" talk to me.
>
> "LANDING
> Normal landings are made power off with any flap setting. Slips are
> prohibited in full flap approaches because of a downward pitch
> encountered under certain combinations of airspeed and sideslip angle."
> ---------------------------------------------------------------------
>
> I wear my "Slips with Flaps" T-Shirt proudly!
>
> Bob Moore
> 12 years instructing in Skyhawks

--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

On Oct 16, 7:52 am, wrote:
> On Oct 16, 12:43 am, Bertie the Bunyip > wrote:
>
>
>
> > wrote in news:1192492570.300275.289550
> > @i38g2000prf.googlegroups.com:
>
> > > On Oct 15, 8:49 am, Bertie the Bunyip > wrote:
>
> > >> The examiner wouldn't allow him to slip because he reckons they are
> > >> dangerous with the flaps out and that he should wiggle the ailerons back
> > >> and forth to lose height. He didn't even want him to slip clean.
>
> > >> Jesus wept.
>
> > >> This examiner had had a fright in a 172 (this was an archer anyway) and
> > >> did not alow anyone to slip with flaps out.
> > >> While I am firmly in the camp that says some cessnas can get a litle
> > >> fuzzy in pitch with full flaps, this is just stupidity incarnate.
>
> > > Shoot. We do slips with full flaps all the time in 172s, have
> > > done so for years, and never had a scare. I wonder if that "Avoid
> > > Slips With Flaps Extended" applied to some earlier models? I'll have
> > > to check the TCDS sometime.
>
> > > Dan
>
> > Dunno. the manual in a 172 makes reference to a possibility of degraded
> > elevator control, but I think it's only a bit of a nod, really.
> > The Bird dog suffers from this ailment big time, though. it has,
> > essentially, the 172's wing, but the flaps go to 60 degrees. I can tell you
> > first hand that blanking of both the rudder and elevator are a very real
> > characteristic of that airplane if you slip it ith full flaps. I did it
> > once close to the ground and never even thought about it again..
>
> Here's what the Type Certificate Data Sheet says:
> .................................................. ..................................
>
> D. On flap handle, Models 172 through 172E
>
> (1) "Flaps - Pull to extend
> Takeoff Retract 0°
> 1st notch 10°
> Landing 0° - 40°
>
> (2) "Avoid slips with flaps down."
>
> E. Near flap indicator Models 172F (electric flaps) through 17271034,
> excluding 17270050)
>
> "Avoid slips with flaps extended."
> .................................................. ........................................
>
> The applicable models, 172 through 172F, were built between
> 1956 and 1964 ('65 model?). There's no mention of the slip with flaps
> thing for later models. I wonder if the addition of the back window
> changed the airflow enough to keep the elevator flying?
>
> Dan

Wait a minute. I just noticed something, and it's not clear
from the way Cessna put it on the TCDS. It says under "E" that the
avoid slips thing applies to the 172F through 17271034. That serial
number is the end of the 1978 172 N production, so the warning applies
to a lot more that I though it did. I hope nobody's gone out and hurt
themselves, now.
But we still slip with full flaps.

Dan

On Oct 16, 11:25 am, Scott > wrote:
> Seems if one must use full flaps AND slip in landing, I would say the
> approach was an abortion that lived. I prefer slips to flaps as you can
> instantly remove a slip but the same can't be said for flaps...
>
> Just MY personal opinion...not trying to slam anybody.

Need to know how to do it for forced approaches. The stress
of an actual failure (I've had two) will make things difficult enough,
and slipping with flap might be the only way to get down soon enough
in the only field available.
I miss manual flaps. They were handy. You could dump them
right at touchdown and get weight on the mains for braking. Electric
flaps are so slow that they are passing through 20°, the max-lift/min
drag position, just when you want to brake, so it's better to leave
them alone. My old Auster had huge Zap flaps that lowered the stall by
a wide margin, and dumping them right at a minimum-speed touchdown
allowed full braking and stopping in unbelievably short spaces.

Dan

> wrote

I miss manual flaps. They were handy. You could dump them
right at touchdown and get weight on the mains for braking. Electric
flaps are so slow that they are passing through 20°, the max-lift/min
drag position, just when you want to brake, so it's better to leave
them alone. My old Auster had huge Zap flaps that lowered the stall by
a wide margin, and dumping them right at a minimum-speed touchdown
allowed full braking and stopping in unbelievably short spaces.

It would be nice if there was a manual release, something like the manual
release on an automatic garage door, then a spring and aerodynamic forces
could pull them back to "dumped."

Hey, something new to add to your design! <g>
--
Jim in NC

Shirl wrote:
>> I spoke with the owners when I helped them move the wreckage
>> around during the repaving (that was interesting!). Apparently,
>> they are not happy with the settlement being offered by the
>> school's insurance company, so they're holding out and
>> considering suing. Until it's all settled, they have to keep the
>> wreckage.
>
>What a nightmare! I was not aware that plane was with a school. Which
>school was it, do you know? Oh well, everyone stops there to look at it!
>;-)

I think we got our wires crossed. You mentioned above that out of control
plane was from one of the local airline pilot factories. That's the school
I'm talking about. It's the pilot factory's insurance that is offering a
settlement. The folks that own the chewed up Bo are holding out for a
better deal.

John Galban=====>N4BQ (PA28-180)

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums.aspx/aviation/200710/1

Newps wrote:

>>> The engine manufacturers are about the last place I'd look for engine
>>> management techniques.

>> Interesting point of view. Please explain.

> Lean of peak. In the face of overwhelming evidence both engine
> manufacturers flat out state that LOP is harmful to your engine.

Not true. Look at
http://www.lycoming.textron.com/support/troubleshooting/resources/SSP700A.pdf

In this paper, Lycoming explains very well why they think that lean of
peak operation works in some environments, but is a bad idea for the
average privat pilot, and why they stopped recommending it in the 60es.
Makes a lot of sense to me.

But you didn't answer my question: Why would the engine manufacturers be
about the last place you'd look for engine management techniques? I take
it that the POH is the last place you'd look for correct aircraft
operation techniques, too?

Thomas Borchert wrote:

>> Which are those companies and where do I find those data?
>>
>
> One is: http://www.gami.com
>
> See:
> http://www.gami.com/gamitcmdefault.html
> http://www.avweb.com/news/pelican/182544-1.html
> http://www.engineteststand.com/
> http://www.advancedpilot.com/


I somehow miss the claimed "hard scientific data". All I see is just
another a company which promotes its own gadgets.

"JGalban via AviationKB.com" <u32749@uwe> wrote:
> I think we got our wires crossed. You mentioned above that out of control
> plane was from one of the local airline pilot factories. That's the school
> I'm talking about. It's the pilot factory's insurance that is offering a
> settlement. The folks that own the chewed up Bo are holding out for a
> better deal.

Yeah, that finally dawned on me after I asked about the school. Chalk it
up to a senior moment!
;-)

Shirl

I think I would still use an agressive slip and then dump the full
flaps as close to touchdown as possible to be SURE you have the field
made. Of course, there will be a fly in the oitment if the forced
landing is due to smoke in the cockpit and you have those electric flaps...

$0.02 worth of free advice ;)

Scott

wrote:
> On Oct 16, 11:25 am, Scott > wrote:
>
>>Seems if one must use full flaps AND slip in landing, I would say the
>>approach was an abortion that lived. I prefer slips to flaps as you can
>>instantly remove a slip but the same can't be said for flaps...
>>
>>Just MY personal opinion...not trying to slam anybody.
>
>
> Need to know how to do it for forced approaches. The stress
> of an actual failure (I've had two) will make things difficult enough,
> and slipping with flap might be the only way to get down soon enough
> in the only field available.
> I miss manual flaps. They were handy. You could dump them
> right at touchdown and get weight on the mains for braking. Electric
> flaps are so slow that they are passing through 20°, the max-lift/min
> drag position, just when you want to brake, so it's better to leave
> them alone. My old Auster had huge Zap flaps that lowered the stall by
> a wide margin, and dumping them right at a minimum-speed touchdown
> allowed full braking and stopping in unbelievably short spaces.
>
> Dan
>

--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

Of course, that system would lead to dumps on short final at about 50
feet up on a nice day under other than emergency conditions (except for
the one just created)...

Scott


Morgans wrote:

> > wrote
>
> I miss manual flaps. They were handy. You could dump them
> right at touchdown and get weight on the mains for braking. Electric
> flaps are so slow that they are passing through 20°, the max-lift/min
> drag position, just when you want to brake, so it's better to leave
> them alone. My old Auster had huge Zap flaps that lowered the stall by
> a wide margin, and dumping them right at a minimum-speed touchdown
> allowed full braking and stopping in unbelievably short spaces.
>
> It would be nice if there was a manual release, something like the manual
> release on an automatic garage door, then a spring and aerodynamic forces
> could pull them back to "dumped."
>
> Hey, something new to add to your design! <g>

--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

Ernest Christley wrote:
> Bertie the Bunyip wrote:
>
>>>> It's the same either way. Cooling and heating are two sides of th
>>>> esame coin. It takes time to disapate heat and it's not so much the
>>>> passage of heat from one area to another (or the disappation, it's
>>>> irrelevant) but the speed at which the cooling or heating is taking
>>>> place and thus the gradient across the material. In short, you take
>>>> a frozen lump of metal and apply a torch to one
>>>> side you have a problem. Take a cherry red pice of metal and put
>>>> some ice on side and you have
>>>> the same problem (more or less, and disregading crystalisation)
>>> It is the same if the same delta T is present, but my point is that it
>>> is easier to heat something quickly than cool it quickly. Even at 250
>>> C, you are only 523 degrees above absolute zero. So, this the
>>> absolute largest delta T you can induce for cooling, and it is very
>>> hard to get absolute zero, so you are more likely to have a cool temp
>>> closer to 0 C yielding a delta T of only 250 degrees.
>>>
>>> On the hot side things are more open-ended. It isn't too hard to get
>>> 450 C exhaust gas temperatures. For an engine that is started at say
>>> 20 C ambient temperature, you now have a delta T of 430 degrees which
>>> is much greater than the 250 likely on the cooling side of the cycle.
>>>
>
> With the heating, you only have the few hundred CFM of air passing
> through the engine to heat it. With the cooling, you have all of the
> great outdoors to do the trick. To tie it into your anology, you have a
> butane lighter to heat the metal, and the Atlantic Ocean to cool it.

The heat doesn't come from the air, but from the fuel.

Matt

Bertie the Bunyip wrote:
> Ernest Christley > wrote in news:47142123$0$32479
> :
>
>> Bertie the Bunyip wrote:
>>
>>>>> It's the same either way. Cooling and heating are two sides of th
>>>>> esame coin. It takes time to disapate heat and it's not so much the
>>>>> passage of heat from one area to another (or the disappation, it's
>>>>> irrelevant) but the speed at which the cooling or heating is taking
>>>>> place and thus the gradient across the material.
>>>>> In short, you take a frozen lump of metal and apply a torch to one
>>>>> side you have a problem.
>>>>> Take a cherry red pice of metal and put some ice on side and you have
>>>>> the same problem (more or less, and disregading crystalisation)
>>>> It is the same if the same delta T is present, but my point is that it
>>>> is easier to heat something quickly than cool it quickly. Even at 250
>>>> C, you are only 523 degrees above absolute zero. So, this the
>>>> absolute largest delta T you can induce for cooling, and it is very
>>>> hard to get absolute zero, so you are more likely to have a cool temp
>>>> closer to 0 C yielding a delta T of only 250 degrees.
>>>>
>>>> On the hot side things are more open-ended. It isn't too hard to get
>>>> 450 C exhaust gas temperatures. For an engine that is started at say
>>>> 20 C ambient temperature, you now have a delta T of 430 degrees which
>>>> is much greater than the 250 likely on the cooling side of the cycle.
>>>>
>> With the heating, you only have the few hundred CFM of air passing
>> through the engine to heat it. With the cooling, you have all of the
>> great outdoors to do the trick. To tie it into your anology, you have a
>> butane lighter to heat the metal, and the Atlantic Ocean to cool it.
>>
>
> Kind of besides th point. you coudl say the same thing about an oxy
> acetylene setup and we all know what that will do to a bit of metal.

Bertie, he thinks the heat comes from the air so trying to explain an
acetylene torch will be a real challenge! :-)

Matt

Steve Hix wrote:

> So they went out one morning, got plenty of cushion between themselves
> and the ground, set the 172 into a landing configuration with full
> flaps, and slipped it.
>
> It shook a bit and then went inverted on them. They recovered and came
> back home.

Got to love those urban legends!

Matt

"Bob Moore" > wrote in message
46.128...
> Bertie the Bunyip wrote
>> This examiner had had a fright in a 172 and
>> did not alow anyone to slip with flaps out.
>> While I am firmly in the camp that says some
>> cessnas can get a litle fuzzy in pitch with
>> full flaps, this is just stupidity incarnate.
>
> About once-a-year I post the following excerpt from "Cessna, Wings for
> the World", a book by William D. Thompson.
>
> Bill Thompson is an Aeronautical engineer from Purdue University and
> worked for Cessna Aircraft Company for 28 years as an engineering test
> pilot and later as the Manager of Flight Test & Aerodynamics.
>
> -------------------------------------------------------------------
> "With the advent of the large slotted flaps in the C-170, C-180, and C-
> 172 we encountered a nose down pitch in forward slips with the wing
> flaps deflected. In some cases it was severe enough to lift the pilot
> against his seat belt if he was slow in checking the motion. For this

great stuff snipped...


>
> I wear my "Slips with Flaps" T-Shirt proudly!
>
> Bob Moore
> 12 years instructing in Skyhawks



Thanks Bob.

Al G, 30 years instructing in Skyhawks

Stefan > wrote:
> Newps wrote:

> >>> The engine manufacturers are about the last place I'd look for engine
> >>> management techniques.

> >> Interesting point of view. Please explain.

> > Lean of peak. In the face of overwhelming evidence both engine
> > manufacturers flat out state that LOP is harmful to your engine.

> Not true. Look at
> http://www.lycoming.textron.com/support/troubleshooting/resources/SSP700A.pdf

> In this paper, Lycoming explains very well why they think that lean of
> peak operation works in some environments, but is a bad idea for the
> average privat pilot, and why they stopped recommending it in the 60es.
> Makes a lot of sense to me.

They didn't have engine analyzers for bug smashers in the 60's.

Everyone endorsing LOP operations bases the the mixture settings
on engine analyzer readings.

--
Jim Pennino

Remove .spam.sux to reply.

Matt Whiting > wrote in
:

> Bertie the Bunyip wrote:
>> Ernest Christley > wrote in
>> news:47142123$0$32479 :
>>
>>> Bertie the Bunyip wrote:
>>>
>>>>>> It's the same either way. Cooling and heating are two sides of th
>>>>>> esame coin. It takes time to disapate heat and it's not so much
>>>>>> the passage of heat from one area to another (or the disappation,
>>>>>> it's irrelevant) but the speed at which the cooling or heating is
>>>>>> taking place and thus the gradient across the material.
>>>>>> In short, you take a frozen lump of metal and apply a torch to
>>>>>> one side you have a problem.
>>>>>> Take a cherry red pice of metal and put some ice on side and you
>>>>>> have the same problem (more or less, and disregading
>>>>>> crystalisation)
>>>>> It is the same if the same delta T is present, but my point is
>>>>> that it is easier to heat something quickly than cool it quickly.
>>>>> Even at 250 C, you are only 523 degrees above absolute zero. So,
>>>>> this the absolute largest delta T you can induce for cooling, and
>>>>> it is very hard to get absolute zero, so you are more likely to
>>>>> have a cool temp closer to 0 C yielding a delta T of only 250
>>>>> degrees.
>>>>>
>>>>> On the hot side things are more open-ended. It isn't too hard to
>>>>> get 450 C exhaust gas temperatures. For an engine that is started
>>>>> at say 20 C ambient temperature, you now have a delta T of 430
>>>>> degrees which is much greater than the 250 likely on the cooling
>>>>> side of the cycle.
>>>>>
>>> With the heating, you only have the few hundred CFM of air passing
>>> through the engine to heat it. With the cooling, you have all of
>>> the great outdoors to do the trick. To tie it into your anology,
>>> you have a butane lighter to heat the metal, and the Atlantic Ocean
>>> to cool it.
>>>
>>
>> Kind of besides th point. you coudl say the same thing about an oxy
>> acetylene setup and we all know what that will do to a bit of metal.
>
> Bertie, he thinks the heat comes from the air so trying to explain an
> acetylene torch will be a real challenge! :-)
>

Mm, possibly..

but to be fair it is partly the air !

Bertie

"Bertie the Bunyip" > wrote

> but to be fair it is partly the air !

Only if you consider the oxy in the tank, as air.
--
Jim in NC

Ernest Christley > wrote in
:

> Matt Whiting wrote:
>> Ernest Christley wrote:
>>> Bertie the Bunyip wrote:
>>>
>>>>>> It's the same either way. Cooling and heating are two sides of th
>>>>>> esame coin. It takes time to disapate heat and it's not so much
>>>>>> the passage of heat from one area to another (or the disappation,
>>>>>> it's irrelevant) but the speed at which the cooling or heating is
>>>>>> taking place and thus the gradient across the material. In short,
>>>>>> you take a frozen lump of metal and apply a torch to one
>>>>>> side you have a problem. Take a cherry red pice of metal and put
>>>>>> some ice on side and you have
>>>>>> the same problem (more or less, and disregading crystalisation)
>>>>> It is the same if the same delta T is present, but my point is
>>>>> that it is easier to heat something quickly than cool it quickly.
>>>>> Even at 250 C, you are only 523 degrees above absolute zero. So,
>>>>> this the absolute largest delta T you can induce for cooling, and
>>>>> it is very hard to get absolute zero, so you are more likely to
>>>>> have a cool temp closer to 0 C yielding a delta T of only 250
>>>>> degrees.
>>>>>
>>>>> On the hot side things are more open-ended. It isn't too hard to
>>>>> get 450 C exhaust gas temperatures. For an engine that is started
>>>>> at say
>>>>> 20 C ambient temperature, you now have a delta T of 430 degrees
>>>>> which is much greater than the 250 likely on the cooling side of
>>>>> the cycle.
>>>>>
>>>
>>> With the heating, you only have the few hundred CFM of air passing
>>> through the engine to heat it. With the cooling, you have all of
>>> the great outdoors to do the trick. To tie it into your anology,
>>> you have a butane lighter to heat the metal, and the Atlantic Ocean
>>> to cool it.
>>
>> The heat doesn't come from the air, but from the fuel.
>>
>> Matt
>
> - Heat comes from the reaction of the fuel vapors with the oxygen in
> the air.
> - Once the fuel is vaporized, isn't it also part of the air.
>
> Semantics aside, the point is, you have a limited amount of BTU
> available from the fuel-air mixture. Since some of those BTU's are
> carried away even as the engine is warming up, the heating will be
> gradual. It will heat until a dynamic equilibrium is reached between
> the heat from combustion and the cooling from air flow. Hopefully at
> 350 degrees F or less.
>
> Pull the heating part of the equation out, and all you have is
> cooling.
> All the air around you is a really large heat sink to dump into.
> Push
> that engine through the air at 100mph, and the heat will come out
> FAST!!
>
> When you cut the power, you cut the heat, but the pistons are still
> moving. The cylinders cool quickly. They're exposed to the air, and
> have lots of vanes designed to give up that heat. The piston is
> insulated...by the cylinder, coatings of oil, etc. The cylinder
> shrinks, clamps the moving piston, and parts give up shortly
> thereafter.
> I'm not brave/fool (you pick) enough to test this, but the engine
> might never crack if you stopped the windmilling when you chop the
> power.
>
> Your welding torch example is not germane.


You have to pump pure
> oxygen into an acetylene flame to get welding temps. Acetylene gives
> up more BTUs that gasoline, and it won't work with normal atmosphere
> which is mostly nitrogen. You won't ever be able to reach the 6000
> degree max temp of a welding flame inside a normal combustion engine.
> Even then, try to weld a dirty piece of metal sometime. Even the
> thinnest coat of crud is enough to insulate the metal enough to make
> welding a frustrating experience.




That's beside the point.


Bertie
>

On Sun, 14 Oct 2007 10:13:15 +0000 (UTC), Bertie the Bunyip >
wrote:

>Matt Whiting > wrote in news:foeQi.309$2n4.18956
:
snippage
>> I'm personally not convinced that Lycoming's recommendations lengthen
>> engine life.
>>
>> Matt
>
>
more snippage
>I think Lycoming probably figured most of this out in the 1920s,
>Continental even earlier.
yet more snippage

Lycoming's more recent (than the 20's) recommendations for increased
longevity on turbo-supercharged engines were primarily based on the
short-lived PA31 "commuter"s which by coincidence had extremely
short-lived engines.

The companies that I allegedly maintained this type of aircraft for
followed these recommendations-that was how I originally allegedly
learned to operate them. And I'm not a "real pilot"-nor do I play one
on TV-just an alleged spannerbender.

We averaged probably 3 premature cylinder removals running 2 engines
to recommended TBO (not an option in a typical Pt135 op). E-guide
would be shot. Of course, by TBO, all the e-guides were shot, but only
a couple would wobble to the point of valve face burnage.

I have allegedly seen similiar engines that needed 6 cylinders removed
after 400-600 hours of operation according to airframe OEM (read
marketing department) performance charts. Hard to tell the owner of a
brand-spanking new Malibu Mirage that he better count on operating at
65%. Was absofreakinglutely hilarious to see how many of them useta be
in Rape-A-Plane with 600 hours and 6 new cylinders.

The you-need-an-engine-analyzer crowd in most cases has never had to
operate any airplane at a profit-nor have they had to try an teach
multiple crews simple and seemingly stupid operating procedures...

Anybody who thinks that "shock-cooling" is a pure "myth" has never
feathered/secured an operating radial engine and watched the CHT
needle drop. I personally have never seen one come up that fast on the
TO roll either.

You really need to get a few more biting comments into this thread,
I'm starting to get concerned about your health.

TC

"Bob Moore" wrote in message...
> I wear my "Slips with Flaps" T-Shirt proudly!
>

Mine's totally worn out, even though I only wore it to fly-in events. I
wonder if Tina will ever resurface and run another batch???

wrote in
:

> On Sun, 14 Oct 2007 10:13:15 +0000 (UTC), Bertie the Bunyip >
> wrote:
>
>>Matt Whiting > wrote in news:foeQi.309$2n4.18956
:
> snippage
>>> I'm personally not convinced that Lycoming's recommendations
lengthen
>>> engine life.
>>>
>>> Matt
>>
>>
> more snippage
>>I think Lycoming probably figured most of this out in the 1920s,
>>Continental even earlier.
> yet more snippage
>
> Lycoming's more recent (than the 20's) recommendations for increased
> longevity on turbo-supercharged engines were primarily based on the
> short-lived PA31 "commuter"s which by coincidence had extremely
> short-lived engines.
>
> The companies that I allegedly maintained this type of aircraft for
> followed these recommendations-that was how I originally allegedly
> learned to operate them. And I'm not a "real pilot"-nor do I play one
> on TV-just an alleged spannerbender.
>
> We averaged probably 3 premature cylinder removals running 2 engines
> to recommended TBO (not an option in a typical Pt135 op). E-guide
> would be shot. Of course, by TBO, all the e-guides were shot, but only
> a couple would wobble to the point of valve face burnage.
>
> I have allegedly seen similiar engines that needed 6 cylinders removed
> after 400-600 hours of operation according to airframe OEM (read
> marketing department) performance charts. Hard to tell the owner of a
> brand-spanking new Malibu Mirage that he better count on operating at
> 65%. Was absofreakinglutely hilarious to see how many of them useta be
> in Rape-A-Plane with 600 hours and 6 new cylinders.
>
> The you-need-an-engine-analyzer crowd in most cases has never had to
> operate any airplane at a profit-nor have they had to try an teach
> multiple crews simple and seemingly stupid operating procedures...
>
> Anybody who thinks that "shock-cooling" is a pure "myth" has never
> feathered/secured an operating radial engine and watched the CHT
> needle drop. I personally have never seen one come up that fast on the
> TO roll either.

Thenkew
>
> You really need to get a few more biting comments into this thread,
> I'm starting to get concerned about your health.
>


I'm tired. I've run out of Ginko.


Bertie
>

In article >,
Matt Whiting > wrote:

> Steve Hix wrote:
>
> > So they went out one morning, got plenty of cushion between themselves
> > and the ground, set the 172 into a landing configuration with full
> > flaps, and slipped it.
> >
> > It shook a bit and then went inverted on them. They recovered and came
> > back home.
>
> Got to love those urban legends!

I was sitting at the FBO front desk when Lynn and Fred went out to see
what would happen, and was there when they returned about a half hour
later.

They told me then what had happened, and agreed that they weren't
inclined to try it again with our 172. They weren't sufficiently
interested to see if it was affected one way or another by changing
payload, CG location, etc.

Not an urban legend, sorry if that disappoints you.

Matt Whiting wrote:
> Bertie the Bunyip wrote:
>> Matt Whiting > wrote in
>
>>> It is the same if the same delta T is present, but my point is that it
>>> is easier to heat something quickly than cool it quickly. Even at 250
>>> C, you are only 523 degrees above absolute zero. So, this the
>>> absolute largest delta T you can induce for cooling, and it is very
>>> hard to get absolute zero, so you are more likely to have a cool temp
>>> closer to 0 C yielding a delta T of only 250 degrees.
>>>
>>> On the hot side things are more open-ended. It isn't too hard to get
>>> 450 C exhaust gas temperatures. For an engine that is started at say
>>> 20 C ambient temperature, you now have a delta T of 430 degrees which
>>> is much greater than the 250 likely on the cooling side of the cycle.
>>>
>>> That is one reason why I suspect that "shock heating" is more likely
>>> to be an issue than "shock cooling." I suspect you can induce a
>>> higher delta T during a full-throttle initial climb than you can
>>> during an idle descent from a cruise power setting.
>>>
>>
>> Right, I'm with you now. yeah, I can buy that. Froma strictly clinical
>> viewpoint it absolutely makes sense. My experience with damage says
>> otherwise, though I can offer no explanation why that should be the
>> case. Years ago I towed gliders with Bird-dogs and we cracked a lot of
>> cylinders when we just closed the throttle after release. When we
>> moved to gradual reduction to ultimately 1500 RPM the problem
>> disappeared completely. Later, when I flew big pistons,the procedures
>> for cooling down the cylinders on the way down. You were almost
>> gaurunteed a crack if you yanked the taps closed. Can't see how we
>> went from cold to hot any more than you would just starting up and
>> taking off. I've just bought an aerobatic airplane with a Lycoming.
>> We're not expecing to get to TBO with the engine because we'll be
>> doing aerobaics with it, but of course we're prepared to live with that.
>> I suppose the point I'm making is that even if shick cooling is over-
>> rated, it certainly does no harm to observe trad practices as if it did.
>
> I suspect, as with most "real world" problems, that there is more in
> play than delta T induced stress. Probably geometry and other factors.
> Maybe having the thin fins on the outside vs. thick metal on the inside
> is making a big difference in the stress profile.
>
> I've not had experience with the larger engines or with radials.
> However, my experience with O-470 and smaller engines is that shock
> cooling just isn't an issue and many folks are paranoid for nothing.
>
> Operating the engine as if shock cooling was an issue is probably not a
> problem in most cases, but if it causes you, as it has with Jay, to not
> practice essential emergency procedures, then I disagree that it causes
> no harm. This may be very harmful should Jay experience an engine
> failure for real.
>
> Matt

Shock cooling damage is merely the effect of different rates of thermal
dimensional change between the aluminum cylinder head and the steel
valve seats and possibly between the head and the barrel where its
threaded on. When contracting, the head shrinks faster than the valve
seats and barrel and huge tension stresses are built up in the area of
the head between the valve and the nearest hole, which is usually the
spark plug. Most shock cooling damage is a crack between the exhaust
valve and the nearest plug hole.

It's not a problem when heating because the head expands faster than the
steel parts so the stress effects are reversed. This is why the
manufacturers have no problem with going from idle to full power as soon
as the engine will take it without stumbling. There is no such thing as
shock heating...

Shock cooling is generally a problem when at the extremes, going from
full power to idle. You won't get enough stress to cause damage going
from cruise power to idle, so for airplanes not used for towing, or
aerobatics or some flight training scenarios, it's not a problem.

John

"J.Kahn" > wrote in
:

> Matt Whiting wrote:
>> Bertie the Bunyip wrote:
>>> Matt Whiting > wrote in
>>
>>>> It is the same if the same delta T is present, but my point is that
>>>> it is easier to heat something quickly than cool it quickly. Even
>>>> at 250 C, you are only 523 degrees above absolute zero. So, this
>>>> the absolute largest delta T you can induce for cooling, and it is
>>>> very hard to get absolute zero, so you are more likely to have a
>>>> cool temp closer to 0 C yielding a delta T of only 250 degrees.
>>>>
>>>> On the hot side things are more open-ended. It isn't too hard to
>>>> get 450 C exhaust gas temperatures. For an engine that is started
>>>> at say 20 C ambient temperature, you now have a delta T of 430
>>>> degrees which is much greater than the 250 likely on the cooling
>>>> side of the cycle.
>>>>
>>>> That is one reason why I suspect that "shock heating" is more
>>>> likely to be an issue than "shock cooling." I suspect you can
>>>> induce a higher delta T during a full-throttle initial climb than
>>>> you can during an idle descent from a cruise power setting.
>>>>
>>>
>>> Right, I'm with you now. yeah, I can buy that. Froma strictly
>>> clinical viewpoint it absolutely makes sense. My experience with
>>> damage says otherwise, though I can offer no explanation why that
>>> should be the case. Years ago I towed gliders with Bird-dogs and we
>>> cracked a lot of cylinders when we just closed the throttle after
>>> release. When we moved to gradual reduction to ultimately 1500 RPM
>>> the problem disappeared completely. Later, when I flew big
>>> pistons,the procedures for cooling down the cylinders on the way
>>> down. You were almost gaurunteed a crack if you yanked the taps
>>> closed. Can't see how we went from cold to hot any more than you
>>> would just starting up and taking off. I've just bought an aerobatic
>>> airplane with a Lycoming. We're not expecing to get to TBO with the
>>> engine because we'll be doing aerobaics with it, but of course we're
>>> prepared to live with that. I suppose the point I'm making is that
>>> even if shick cooling is over- rated, it certainly does no harm to
>>> observe trad practices as if it did.
>>
>> I suspect, as with most "real world" problems, that there is more in
>> play than delta T induced stress. Probably geometry and other
>> factors.
>> Maybe having the thin fins on the outside vs. thick metal on the
>> inside
>> is making a big difference in the stress profile.
>>
>> I've not had experience with the larger engines or with radials.
>> However, my experience with O-470 and smaller engines is that shock
>> cooling just isn't an issue and many folks are paranoid for nothing.
>>
>> Operating the engine as if shock cooling was an issue is probably not
>> a problem in most cases, but if it causes you, as it has with Jay, to
>> not practice essential emergency procedures, then I disagree that it
>> causes no harm. This may be very harmful should Jay experience an
>> engine failure for real.
>>
>> Matt
>
> Shock cooling damage is merely the effect of different rates of
> thermal dimensional change between the aluminum cylinder head and the
> steel valve seats and possibly between the head and the barrel where
> its threaded on. When contracting, the head shrinks faster than the
> valve seats and barrel and huge tension stresses are built up in the
> area of the head between the valve and the nearest hole, which is
> usually the spark plug. Most shock cooling damage is a crack between
> the exhaust valve and the nearest plug hole.
>
> It's not a problem when heating because the head expands faster than
> the steel parts so the stress effects are reversed. This is why the
> manufacturers have no problem with going from idle to full power as
> soon as the engine will take it without stumbling. There is no such
> thing as shock heating...
>
> Shock cooling is generally a problem when at the extremes, going from
> full power to idle. You won't get enough stress to cause damage
> going from cruise power to idle, so for airplanes not used for towing,
> or aerobatics or some flight training scenarios, it's not a problem.
>


I can buy that..

Bertie
>

"J.Kahn" > wrote

> Shock cooling damage is merely the effect of different rates of thermal
> dimensional change between the aluminum cylinder head and the steel valve
> seats and possibly between the head and the barrel where its threaded on.
> When contracting, the head shrinks faster than the valve seats and barrel
> and huge tension stresses are built up in the area of the head between the
> valve and the nearest hole, which is usually the spark plug. Most shock
> cooling damage is a crack between the exhaust valve and the nearest plug
> hole.
>
> It's not a problem when heating because the head expands faster than the
> steel parts so the stress effects are reversed. This is why the
> manufacturers have no problem with going from idle to full power as soon
> as the engine will take it without stumbling. There is no such thing as
> shock heating...
>
> Shock cooling is generally a problem when at the extremes, going from full
> power to idle. You won't get enough stress to cause damage going from
> cruise power to idle, so for airplanes not used for towing, or aerobatics
> or some flight training scenarios, it's not a problem.

Yours is the first explanation that I can believe. Thanks.

I can also believe that cruise power to idle is not a huge problem, and that
perhaps it is even more true if the airspeed is kept down a bit, while the
power comes off.
--
Jim in NC

Steve Hix wrote:
> In article >,
> Matt Whiting > wrote:
>
>> Steve Hix wrote:
>>
>>> So they went out one morning, got plenty of cushion between themselves
>>> and the ground, set the 172 into a landing configuration with full
>>> flaps, and slipped it.
>>>
>>> It shook a bit and then went inverted on them. They recovered and came
>>> back home.
>> Got to love those urban legends!
>
> I was sitting at the FBO front desk when Lynn and Fred went out to see
> what would happen, and was there when they returned about a half hour
> later.
>
> They told me then what had happened, and agreed that they weren't
> inclined to try it again with our 172. They weren't sufficiently
> interested to see if it was affected one way or another by changing
> payload, CG location, etc.
>
> Not an urban legend, sorry if that disappoints you.

I don't for a second believe that a slip with flaps turned them over. I
suspect they STALLED it and went inverted, but that wasn't due to a slip
with flaps.

Matt

J.Kahn wrote:

> It's not a problem when heating because the head expands faster than the
> steel parts so the stress effects are reversed. This is why the
> manufacturers have no problem with going from idle to full power as soon
> as the engine will take it without stumbling. There is no such thing as
> shock heating...

What about the aluminum piston in the steel cylinder?

Matt

In article >,
Matt Whiting > wrote:

> Steve Hix wrote:
> > In article >,
> > Matt Whiting > wrote:
> >
> >> Steve Hix wrote:
> >>
> >>> So they went out one morning, got plenty of cushion between themselves
> >>> and the ground, set the 172 into a landing configuration with full
> >>> flaps, and slipped it.
> >>>
> >>> It shook a bit and then went inverted on them. They recovered and came
> >>> back home.
> >> Got to love those urban legends!
> >
> > I was sitting at the FBO front desk when Lynn and Fred went out to see
> > what would happen, and was there when they returned about a half hour
> > later.
> >
> > They told me then what had happened, and agreed that they weren't
> > inclined to try it again with our 172. They weren't sufficiently
> > interested to see if it was affected one way or another by changing
> > payload, CG location, etc.
> >
> > Not an urban legend, sorry if that disappoints you.
>
> I don't for a second believe that a slip with flaps turned them over. I
> suspect they STALLED it and went inverted, but that wasn't due to a slip
> with flaps.

Kewl. Believe whatever floats your boat.

They were both experienced CFIs, one with a good deal of A-26 and T-28
time. If they'd stalled it, I would think they'd said so.

Steve Hix wrote:
> In article >,
> Matt Whiting > wrote:
>
>
>>Steve Hix wrote:
>>
>>>In article >,
>>> Matt Whiting > wrote:
>>>
>>>
>>>>Steve Hix wrote:
>>>>
>>>>
>>>>>So they went out one morning, got plenty of cushion between themselves
>>>>>and the ground, set the 172 into a landing configuration with full
>>>>>flaps, and slipped it.
>>>>>
>>>>>It shook a bit and then went inverted on them. They recovered and came
>>>>>back home.
>>>>
>>>>Got to love those urban legends!
>>>
>>>I was sitting at the FBO front desk when Lynn and Fred went out to see
>>>what would happen, and was there when they returned about a half hour
>>>later.
>>>
>>>They told me then what had happened, and agreed that they weren't
>>>inclined to try it again with our 172. They weren't sufficiently
>>>interested to see if it was affected one way or another by changing
>>>payload, CG location, etc.
>>>
>>>Not an urban legend, sorry if that disappoints you.
>>
>>I don't for a second believe that a slip with flaps turned them over. I
>>suspect they STALLED it and went inverted, but that wasn't due to a slip
>>with flaps.
>
>
> Kewl. Believe whatever floats your boat.
>
> They were both experienced CFIs, one with a good deal of A-26 and T-28
> time. If they'd stalled it, I would think they'd said so.

It did not go inverted from slipping with flaps.

Matt Whiting > wrote in
:

> J.Kahn wrote:
>
>> It's not a problem when heating because the head expands faster than
>> the steel parts so the stress effects are reversed. This is why the
>> manufacturers have no problem with going from idle to full power as
>> soon as the engine will take it without stumbling. There is no such
>> thing as shock heating...
>
> What about the aluminum piston in the steel cylinder?
>

That can happen too! But the clearances are cgrater ther than it would be
in a valve stem or head to cylinder seat.

Bertie

Steve Hix wrote:
> In article >,
> Matt Whiting > wrote:
>
>> Steve Hix wrote:
>>> In article >,
>>> Matt Whiting > wrote:
>>>
>>>> Steve Hix wrote:
>>>>
>>>>> So they went out one morning, got plenty of cushion between themselves
>>>>> and the ground, set the 172 into a landing configuration with full
>>>>> flaps, and slipped it.
>>>>>
>>>>> It shook a bit and then went inverted on them. They recovered and came
>>>>> back home.
>>>> Got to love those urban legends!
>>> I was sitting at the FBO front desk when Lynn and Fred went out to see
>>> what would happen, and was there when they returned about a half hour
>>> later.
>>>
>>> They told me then what had happened, and agreed that they weren't
>>> inclined to try it again with our 172. They weren't sufficiently
>>> interested to see if it was affected one way or another by changing
>>> payload, CG location, etc.
>>>
>>> Not an urban legend, sorry if that disappoints you.
>> I don't for a second believe that a slip with flaps turned them over. I
>> suspect they STALLED it and went inverted, but that wasn't due to a slip
>> with flaps.
>
> Kewl. Believe whatever floats your boat.
>
> They were both experienced CFIs, one with a good deal of A-26 and T-28
> time. If they'd stalled it, I would think they'd said so.

Likewise, believe all of the urban legends you want.

Matt

On Fri, 19 Oct 2007 11:05:32 +0000 (UTC), Bertie the Bunyip >
wrote:

>Matt Whiting > wrote in
:
>
>> J.Kahn wrote:
>>
>>> It's not a problem when heating because the head expands faster than
>>> the steel parts so the stress effects are reversed. This is why the
>>> manufacturers have no problem with going from idle to full power as
>>> soon as the engine will take it without stumbling. There is no such
>>> thing as shock heating...
>>
>> What about the aluminum piston in the steel cylinder?
>>
>
>That can happen too! But the clearances are cgrater ther than it would be
>in a valve stem or head to cylinder seat.

If we had that kind of piston to cylinder clearance in an automotive
engine we'd think it was worn out. <:-)) At least in the "old days".

Roger (K8RI)

>
>Bertie

"Roger (K8RI)" > wrote in
:

> On Fri, 19 Oct 2007 11:05:32 +0000 (UTC), Bertie the Bunyip >
> wrote:
>
>>Matt Whiting > wrote in
:
>>
>>> J.Kahn wrote:
>>>
>>>> It's not a problem when heating because the head expands faster
>>>> than the steel parts so the stress effects are reversed. This is
>>>> why the manufacturers have no problem with going from idle to full
>>>> power as soon as the engine will take it without stumbling. There
>>>> is no such thing as shock heating...
>>>
>>> What about the aluminum piston in the steel cylinder?
>>>
>>
>>That can happen too! But the clearances are cgrater ther than it would
>>be in a valve stem or head to cylinder seat.
>
> If we had that kind of piston to cylinder clearance in an automotive
> engine we'd think it was worn out. <:-)) At least in the "old days".
>


Yes, some air cooled engines have tapered bores (when cold) to allow for
different rates of expansion in cylinder base-to-head so that it's
perfectly cylindrical when up to temp, but i don't know of any aircraft
engines that have that feature.



Bertie

Steve Hix wrote:
>
> Kewl. Believe whatever floats your boat.
>
> They were both experienced CFIs, one with a good deal of A-26 and T-28
> time. If they'd stalled it, I would think they'd said so.


Why belabor the painfully obvious?

In article >,
Matt Whiting > wrote:

> Steve Hix wrote:
> > In article >,
> > Matt Whiting > wrote:
> >
> >> Steve Hix wrote:
> >>> In article >,
> >>> Matt Whiting > wrote:
> >>>
> >>>> Steve Hix wrote:
> >>>>
> >>>>> So they went out one morning, got plenty of cushion between themselves
> >>>>> and the ground, set the 172 into a landing configuration with full
> >>>>> flaps, and slipped it.
> >>>>>
> >>>>> It shook a bit and then went inverted on them. They recovered and came
> >>>>> back home.
> >>>> Got to love those urban legends!
> >>> I was sitting at the FBO front desk when Lynn and Fred went out to see
> >>> what would happen, and was there when they returned about a half hour
> >>> later.
> >>>
> >>> They told me then what had happened, and agreed that they weren't
> >>> inclined to try it again with our 172. They weren't sufficiently
> >>> interested to see if it was affected one way or another by changing
> >>> payload, CG location, etc.
> >>>
> >>> Not an urban legend, sorry if that disappoints you.
> >> I don't for a second believe that a slip with flaps turned them over.

On second take, agreed.

> >> I suspect they STALLED it and went inverted, but that wasn't due to a slip
> >> with flaps.

Or a stall, alone.

On first pass, I read it as either/or, rather than combination.

> > Kewl. Believe whatever floats your boat.
> >
> > They were both experienced CFIs, one with a good deal of A-26 and T-28
> > time. If they'd stalled it, I would think they'd said so.
>
> Likewise, believe all of the urban legends you want.

Look, it was 30+ years ago. I was barely paying attention at the time,
and not knowing where either are today, I can't very well ask them for
more information.

Did whatever happen result solely from slipping with full flaps? I
really doubt it, unless they were at some extreme weight/CG limit (both
of them being average size, probably not).

So yeah, they likely did something else at the time that carried things
further. Stall alone? Doubt it. Slip with full flaps alone. Doubt it.

I still wouldn't want to play with something against which the aircraft
is placarded, not without a lot of cushion.

As for urban legend, you looking at the wrong guy. Spent too much time
studying physics/chemistry, and working in systems engineering for that.
(And doubly skeptical of conspiracy nonsense.)

And I apologize for blowing you off earlier; it's been a series of bad
months at work (I avoided the layoff, not everyone else in the group
did), and working 6 1/2 day weeks for 10 to 14 hrs/day for the last
month hasn't helped. Mea culpa.

Meanwhile, in Dec. I take off for what's going to turn out to be the
better part of four weeks vacation (else I start losing what's
accumulated), and after 31 years, get back into flying.

I may end up being civil by then.

"Bertie the Bunyip" > wrote

> Yes, some air cooled engines have tapered bores (when cold) to allow for
> different rates of expansion in cylinder base-to-head so that it's
> perfectly cylindrical when up to temp, but i don't know of any aircraft
> engines that have that feature.

Really? I thought that they did have a tighter bore at the top. I guess I
read wrong, or remember wrong.
--
Jim in NC

"Morgans" > wrote in
:

>
> "Bertie the Bunyip" > wrote
>
>> Yes, some air cooled engines have tapered bores (when cold) to allow
>> for different rates of expansion in cylinder base-to-head so that
>> it's perfectly cylindrical when up to temp, but i don't know of any
>> aircraft engines that have that feature.
>
> Really? I thought that they did have a tighter bore at the top. I
> guess I read wrong, or remember wrong.

Maybe. I didn't know that they did. It would make sense if they did, all
right. I don't do machining. I just run my fingers over the pretty parts
when they come out of the machine shop!

Bertie

Steve Hix wrote:

> And I apologize for blowing you off earlier; it's been a series of bad
> months at work (I avoided the layoff, not everyone else in the group
> did), and working 6 1/2 day weeks for 10 to 14 hrs/day for the last
> month hasn't helped. Mea culpa.
>
> Meanwhile, in Dec. I take off for what's going to turn out to be the
> better part of four weeks vacation (else I start losing what's
> accumulated), and after 31 years, get back into flying.
>
> I may end up being civil by then.

Steve, don't sweat it. I enjoy a good debate and rarely take offense at
anything and certainly took no offense at your comments as they were
quite civil.

Cheers,
Matt

>>> Yes, some air cooled engines have tapered bores (when cold) to allow
>>> for different rates of expansion in cylinder base-to-head so that
>>> it's perfectly cylindrical when up to temp, but i don't know of any
>>> aircraft engines that have that feature.
>>
>> Really? I thought that they did have a tighter bore at the top. I
>> guess I read wrong, or remember wrong.
>
> Maybe. I didn't know that they did. It would make sense if they did, all
> right. I don't do machining. I just run my fingers over the pretty parts
> when they come out of the machine shop!

This ought to be an easy question for someone in the group. Surely, there
is someone that does do machining on engines that hangs out here, that would
know for sure.

Anyone?
--
Jim in NC

On Oct 20, 4:41 am, "Morgans" > wrote:
> >>> Yes, some air cooled engines have tapered bores (when cold) to allow
> >>> for different rates of expansion in cylinder base-to-head so that
> >>> it's perfectly cylindrical when up to temp, but i don't know of any
> >>> aircraft engines that have that feature.
>
> >> Really? I thought that they did have a tighter bore at the top. I
> >> guess I read wrong, or remember wrong.
>
> > Maybe. I didn't know that they did. It would make sense if they did, all
> > right. I don't do machining. I just run my fingers over the pretty parts
> > when they come out of the machine shop!
>
> This ought to be an easy question for someone in the group. Surely, there
> is someone that does do machining on engines that hangs out here, that would
> know for sure.
>
> Anyone?
> --
> Jim in NC

Ok, First off don't call me Surely. <GGGG>.
The concept is question is called "choke bore" and the idea is the
bottom of the cylinder that's close to the case runs at a much lower
temp since combustion happens at the other end. The top end grows at a
greater rate because of this. In theory when the engine is up to temp
the cylinder ends up being pretty straight. I have the specs around
here somewhere but if I remember correctly the bore when cold is in
the .006-.008 smaller at the top. Boring one is usually done by using
a tool post grinder and performing the taper feature is a calculated
process. Honing one with a flex hone is straight forward and easy,
using a Sunnen CK-10 or a CV-616 takes ALOT more practice...

Ben
www.haaspowerair.com

" > wrote in
ups.com:

> On Oct 20, 4:41 am, "Morgans" > wrote:
>> >>> Yes, some air cooled engines have tapered bores (when cold) to
>> >>> allow for different rates of expansion in cylinder base-to-head
>> >>> so that it's perfectly cylindrical when up to temp, but i don't
>> >>> know of any aircraft engines that have that feature.
>>
>> >> Really? I thought that they did have a tighter bore at the top.
>> >> I guess I read wrong, or remember wrong.
>>
>> > Maybe. I didn't know that they did. It would make sense if they
>> > did, all right. I don't do machining. I just run my fingers over
>> > the pretty parts when they come out of the machine shop!
>>
>> This ought to be an easy question for someone in the group. Surely,
>> there is someone that does do machining on engines that hangs out
>> here, that would know for sure.
>>
>> Anyone?
>> --
>> Jim in NC
>
> Ok, First off don't call me Surely. <GGGG>.
> The concept is question is called "choke bore" and the idea is the
> bottom of the cylinder that's close to the case runs at a much lower
> temp since combustion happens at the other end. The top end grows at a
> greater rate because of this. In theory when the engine is up to temp
> the cylinder ends up being pretty straight. I have the specs around
> here somewhere but if I remember correctly the bore when cold is in
> the .006-.008 smaller at the top. Boring one is usually done by using
> a tool post grinder and performing the taper feature is a calculated
> process. Honing one with a flex hone is straight forward and easy,
> using a Sunnen CK-10 or a CV-616 takes ALOT more practice...

And I thought it was just my old model airplane engines and bikes that
had that feature. Who would have guessed a Lycoming could clamber to the
height of sophistication reached by Ohlsson and Rice?

Bertie
>

On Sat, 20 Oct 2007 12:31:57 +0000 (UTC), Bertie the Bunyip >
wrote:

snip

>And I thought it was just my old model airplane engines and bikes that
>had that feature. Who would have guessed a Lycoming could clamber to the
>height of sophistication reached by Ohlsson and Rice?
>
>Bertie

Been awhile since Continental spec'ed a choke bore, unsure if Lycoming
ever did (I've never come across one-does not mean it does not exist).

What is curious is that on the Conti's you could "straighten out" the
choke and be within service limits in most cases.

Factory new Lycoming cylinders can tend to be a little smaller at the
upper 1/4 of the bore, but that's because the head gets shrunk onto
the cylinder after it is initially machined & nitrided. Sorta
important to check min. ring gap up there when working with a new jug.

Again, it can be a straight bore and be within new & service limits.

TC

wrote in news:ec1lh3tqmfri1006j5c5nqsbho0g0mnidi@
4ax.com:

> On Sat, 20 Oct 2007 12:31:57 +0000 (UTC), Bertie the Bunyip >
> wrote:
>
> snip
>
>>And I thought it was just my old model airplane engines and bikes that
>>had that feature. Who would have guessed a Lycoming could clamber to the
>>height of sophistication reached by Ohlsson and Rice?
>>
>>Bertie
>
> Been awhile since Continental spec'ed a choke bore, unsure if Lycoming
> ever did (I've never come across one-does not mean it does not exist).
>
> What is curious is that on the Conti's you could "straighten out" the
> choke and be within service limits in most cases.
>
> Factory new Lycoming cylinders can tend to be a little smaller at the
> upper 1/4 of the bore, but that's because the head gets shrunk onto
> the cylinder after it is initially machined & nitrided. Sorta
> important to check min. ring gap up there when working with a new jug.
>
> Again, it can be a straight bore and be within new & service limits
>


Learn sumpin new every day!

Bertie
>

> wrote in message
ups.com...
On Oct 16, 12:43 am, Bertie the Bunyip > wrote:
> wrote in news:1192492570.300275.289550
> @i38g2000prf.googlegroups.com:
>
>
>
> > On Oct 15, 8:49 am, Bertie the Bunyip > wrote:
>
> >> The examiner wouldn't allow him to slip because he reckons they are
> >> dangerous with the flaps out and that he should wiggle the ailerons
> >> back
> >> and forth to lose height. He didn't even want him to slip clean.
>
> >> Jesus wept.
>
> >> This examiner had had a fright in a 172 (this was an archer anyway) and
> >> did not alow anyone to slip with flaps out.
> >> While I am firmly in the camp that says some cessnas can get a litle
> >> fuzzy in pitch with full flaps, this is just stupidity incarnate.
>
> > Shoot. We do slips with full flaps all the time in 172s, have
> > done so for years, and never had a scare. I wonder if that "Avoid
> > Slips With Flaps Extended" applied to some earlier models? I'll have
> > to check the TCDS sometime.
>
> > Dan
>
> Dunno. the manual in a 172 makes reference to a possibility of degraded
> elevator control, but I think it's only a bit of a nod, really.
> The Bird dog suffers from this ailment big time, though. it has,
> essentially, the 172's wing, but the flaps go to 60 degrees. I can tell
> you
> first hand that blanking of both the rudder and elevator are a very real
> characteristic of that airplane if you slip it ith full flaps. I did it
> once close to the ground and never even thought about it again..

Here's what the Type Certificate Data Sheet says:
.................................................. ..................................

D. On flap handle, Models 172 through 172E

(1) "Flaps - Pull to extend
Takeoff Retract 0°
1st notch 10°
Landing 0° - 40°

(2) "Avoid slips with flaps down."

E. Near flap indicator Models 172F (electric flaps) through 17271034,
excluding 17270050)

"Avoid slips with flaps extended."
.................................................. ........................................

The applicable models, 172 through 172F, were built between
1956 and 1964 ('65 model?). There's no mention of the slip with flaps
thing for later models. I wonder if the addition of the back window
changed the airflow enough to keep the elevator flying?

Dan

I believe that the advice against slips with (full) flaps ended when the
maximum flap extension changed from 40 to 30 degrees.

On the very early swept tail 172 (1959 model, IIRC) that I had some time in,
a slip with full flaps resulted in a buffet--but I don't recall that being
done with aft CG at any time that I was aboard.

Peter

"Scott" > wrote in message
.. .
> Of course, that system would lead to dumps on short final at about 50 feet
> up on a nice day under other than emergency conditions (except for the one
> just created)...
>
> Scott
>
There really is a big difference between dumping the flaps, and bringing
them quickly back to the point of greatest lift relative to added
drag--usually around 20 degrees. I've had instructors who insisted on
milking the flaps off, despite the contrary advice in the POH.

Peter

"Peter Dohm" > wrote in
:

>
> "Scott" > wrote in message
> .. .
>> Of course, that system would lead to dumps on short final at about 50
>> feet up on a nice day under other than emergency conditions (except
>> for the one just created)...
>>
>> Scott
>>
> There really is a big difference between dumping the flaps, and
> bringing them quickly back to the point of greatest lift relative to
> added drag--usually around 20 degrees. I've had instructors who
> insisted on milking the flaps off, despite the contrary advice in the
> POH.
>


Well, ultimately you will get the best rate of climb clean after you have
reached best limb speed, of course, but it's not al that significant at the
begining unless you have a big obstacle problem off in the distance, so
you're right, best flap position is usually around 20 or 15 or whatever is
handy!


Bertie

Ï "Bertie the Bunyip" > Ýãñáøå óôï ìÞíõìá
...
>
> Well, ultimately you will get the best rate of climb clean after you have
> reached best limb speed, of course, but it's not al that significant at
> the
> begining unless you have a big obstacle problem off in the distance, so
> you're right, best flap position is usually around 20 or 15 or whatever is
> handy! >
>
> Bertie


An old rule-of-thumb I remember has it that aligning the flap with a down
aileron gives you the best (most lift) flap position (assuming, i presume,
that the ailerons deflect to maximum effectiveness=lift).
FWIW, G.

"gpaleo" > wrote in
news:1192979491.466999@athprx03:

> Ï "Bertie the Bunyip" > Ýãñáøå óôï ìÞíõìá
> ...
>>
>> Well, ultimately you will get the best rate of climb clean after you
>> have reached best limb speed, of course, but it's not al that
>> significant at the
>> begining unless you have a big obstacle problem off in the distance,
>> so you're right, best flap position is usually around 20 or 15 or
>> whatever is handy! >
>>
>> Bertie
>
>
> An old rule-of-thumb I remember has it that aligning the flap with a
> down aileron gives you the best (most lift) flap position (assuming, i
> presume, that the ailerons deflect to maximum effectiveness=lift)

Never heard it but it sounds like a good bush piloty sort of thing to do.




Bertie
>
>

On Oct 21, 7:56 pm, Bertie the Bunyip > wrote:
> "gpaleo" > wrote innews:1192979491.466999@athprx03:
>
>
>
>
>
> > Ï "Bertie the Bunyip" > Ýãñáøå óôï ìÞíõìá
> ...
>
> >> Well, ultimately you will get the best rate of climb clean after you
> >> have reached best limb speed, of course, but it's not al that
> >> significant at the
> >> begining unless you have a big obstacle problem off in the distance,
> >> so you're right, best flap position is usually around 20 or 15 or
> >> whatever is handy! >
>
> >> Bertie
>
> > An old rule-of-thumb I remember has it that aligning the flap with a
> > down aileron gives you the best (most lift) flap position (assuming, i
> > presume, that the ailerons deflect to maximum effectiveness=lift)
>
> Never heard it but it sounds like a good bush piloty sort of thing to do.
>
> Bertie
>
>
>
> - Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -

Hence the reason why some of us fly planes that have flaperons instead
of flaps/ailerons..

" > wrote in
oups.com:

> On Oct 21, 7:56 pm, Bertie the Bunyip > wrote:
>> "gpaleo" > wrote
>> innews:1192979491.466999@athprx03:
>>
>>
>>
>>
>>
>> > Ï "Bertie the Bunyip" > Ýãñáøå óôï ìÞ
> íõìá
>> ...
>>
>> >> Well, ultimately you will get the best rate of climb clean after
>> >> you have reached best limb speed, of course, but it's not al that
>> >> significant at the
>> >> begining unless you have a big obstacle problem off in the
>> >> distance, so you're right, best flap position is usually around 20
>> >> or 15 or whatever is handy! >
>>
>> >> Bertie
>>
>> > An old rule-of-thumb I remember has it that aligning the flap with
>> > a down aileron gives you the best (most lift) flap position
>> > (assuming, i presume, that the ailerons deflect to maximum
>> > effectiveness=lift)
>>
>> Never heard it but it sounds like a good bush piloty sort of thing to
>> do.
>>
>> Bertie
>>
>>
>>
>> - Hide quoted text -
>>
>> - Show quoted text -- Hide quoted text -
>>
>> - Show quoted text -
>
> Hence the reason why some of us fly planes that have flaperons instead
> of flaps/ailerons..
>
>


Eh,OK.

Bertie

Big John > wrote in
:

>
> Bertie
>
> Did you read "Nobody believed that we walked away" that I posted about
> Bud Warrens crash near here in Houston?
>

Yes, I did. Very good.


> I probably should have used a different title but that is how the
> newspaper article in paper was headed.
>
> Good Pilot and very lucky.
>

Absolutely!


Bertie

In article >,
Bertie the Bunyip > wrote:

> > An old rule-of-thumb I remember has it that aligning the flap with a
> > down aileron gives you the best (most lift) flap position (assuming, i
> > presume, that the ailerons deflect to maximum effectiveness=lift)
>
> Never heard it but it sounds like a good bush piloty sort of thing to do.

My flight instructor, a former drug-smuggler, taught me that very
technique.

Dan Nafe wrote:

> In article >,
> Bertie the Bunyip > wrote:
>
>
>>>An old rule-of-thumb I remember has it that aligning the flap with a
>>>down aileron gives you the best (most lift) flap position (assuming, i
>>>presume, that the ailerons deflect to maximum effectiveness=lift)
>>
>>Never heard it but it sounds like a good bush piloty sort of thing to do.
>
>
> My flight instructor, a former drug-smuggler, taught me that very
> technique.


The most lift is always gained with the most flaps.

"Newps" > wrote in message
. ..
>
>
> Dan Nafe wrote:
>
>> In article >,
>> Bertie the Bunyip > wrote:
>>
>>
>>>>An old rule-of-thumb I remember has it that aligning the flap with a
>>>>down aileron gives you the best (most lift) flap position (assuming, i
>>>>presume, that the ailerons deflect to maximum effectiveness=lift)
>>>
>>>Never heard it but it sounds like a good bush piloty sort of thing to do.
>>
>>
>> My flight instructor, a former drug-smuggler, taught me that very
>> technique.
>
>
> The most lift is always gained with the most flaps.

I try to shy away from the use of the word "always". There are some
aircraft that use flaps for their induced drag. An example is a glider with
large span 90 degree flaps. As an owner of such a craft I can testify that
increased lift is not associated with flap setting greater then 40 degrees.
Setting beyond 45 definitely exist only for the drag they create.
(http://tinyurl.com/2w6fuk)

Wayne
HP-14 "6F"
http://www.soaridaho.com/Schreder

In article >,
Newps > wrote:

> Dan Nafe wrote:
>
> > In article >,
> > Bertie the Bunyip > wrote:
> >
> >
> >>>An old rule-of-thumb I remember has it that aligning the flap with a
> >>>down aileron gives you the best (most lift) flap position (assuming, i
> >>>presume, that the ailerons deflect to maximum effectiveness=lift)
> >>
> >>Never heard it but it sounds like a good bush piloty sort of thing to do.
> >
> >
> > My flight instructor, a former drug-smuggler, taught me that very
> > technique.
>
>
> The most lift is always gained with the most flaps.

Really?

Even if true, you sometimes end up picking up drag faster than increased
lift at extreme flap settings, depending on the aircraft.

Steve Hix wrote:


>>The most lift is always gained with the most flaps.
>
>
> Really?
>
> Even if true, you sometimes end up picking up drag faster than increased
> lift at extreme flap settings, depending on the aircraft.


On your typical Cessna 152, 172, 182 206, etc the most lift for the
least drag is approx 20 degrees. Flaps at 40 degrees gives you the most
lift but also more drag than at 20 degrees. Just depends on what you're
trying to accomplish. The first 20 years of Bonanza production there
wasn't a flap indicator in the aircraft, don't have one in mine. The
factory put a stripe that you could line up with the trailing edge of
the wing to get 20 degrees. Those disappear with the first paint job.

On Mon, 05 Nov 2007 16:53:42 -0700, Newps > wrote:

>
>
>Steve Hix wrote:
>
>
>>>The most lift is always gained with the most flaps.
>>
>>
>> Really?
>>
>> Even if true, you sometimes end up picking up drag faster than increased
>> lift at extreme flap settings, depending on the aircraft.
>
>
>On your typical Cessna 152, 172, 182 206, etc the most lift for the
>least drag is approx 20 degrees. Flaps at 40 degrees gives you the most
>lift but also more drag than at 20 degrees. Just depends on what you're
>trying to accomplish. The first 20 years of Bonanza production there
>wasn't a flap indicator in the aircraft, don't have one in mine. The


One thousand one...Onethousand two...onethousand threee...
Who needs marks or indicators?

Roger (K8RI)

>factory put a stripe that you could line up with the trailing edge of
>the wing to get 20 degrees. Those disappear with the first paint job.

> factory put a stripe that you could line up with the trailing edge of
> the wing to get 20 degrees. Those disappear with the first paint job.

I'll bet there's a Gummint regulation that sez you can't hide that stripe.
:)

Rich S.

In article >,
"Rich S." > wrote:

> > factory put a stripe that you could line up with the trailing edge of
> > the wing to get 20 degrees. Those disappear with the first paint job.
>
> I'll bet there's a Gummint regulation that sez you can't hide that stripe.
> :)
>
> Rich S.
>
>

I re-marked mine with a Sharpie.