Engine out practice

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