Practicing SFLs with a constant speed prop - how?

In article ,
wrote:



Whether or not the engine is "running" if the rpm is below this range,
moving the prop control has no effect on the pitch of the prop.


That's what I thought until I tried it on my 182. Idle power, trimmed
stable 80 mph glide with the prop control all the way forward. Pulled
the blue knob back and watched the airspeed increase about 5MPH...pushed
the blue knob in and I slowed again.

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html

With our Mooney F model at best glide speed when I pull the prop control all
the way back (max pitch), it saves me about 300 fpm while maintaining best
glide. With a minimum pitch, the blades are one big braking force.

"Dale" wrote in message
...
In article ,
wrote:



Whether or not the engine is "running" if the rpm is below this range,
moving the prop control has no effect on the pitch of the prop.


That's what I thought until I tried it on my 182. Idle power, trimmed
stable 80 mph glide with the prop control all the way forward. Pulled
the blue knob back and watched the airspeed increase about 5MPH...pushed
the blue knob in and I slowed again.

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html

I don't buy that. I can play with the prop at IDLE and zero knots and
get it to change RPM. My run-up is done at 1700 and the prop oil wash
exercise has a big effect.

Ed

On Mon, 12 Apr 2004 18:06:09 -0400, wrote:

On Mon, 12 Apr 2004 05:06:12 GMT, Ed wrote:

snip

In idle, with the prop at flat pitch, it feels too draggy and comes
down like a rock. With it at high pitch, it seems to have too
optimistic a glide ratio. What's the happy medium?

I'm a little confused by this portion of your question, and a couple
of the replies.

I have never actually messed around a bunch with airspeed/descent
rate/idle engine/prop rpm, but am pretty familiar with how a typical
pressure-to-increase pitch constant-speed prop/governor works.

Somewhere around 1600-1800 rpm, the prop governor ceases to output
enuff pressure to change/maintain the propeller pitch, and the
propeller goes to flat pitch. I've seen it on a gov bench, and on
approach-to-land.

Whether or not the engine is "running" if the rpm is below this range,
moving the prop control has no effect on the pitch of the prop.

TC

snip

I just want to clear this up. My home field (O17) - and just about
all those around it for 50nm are heavily wooded and surrounded by
pines reaching up about 50'.

Some of you guys are men to faith, obviously. I however, am not and
prefer to try to perfect the simulation rather than log glider time.
My goal is simply to set it up so the configuration for best glide or
min sink (depending on distance to the runway) so as to get a feel for
expected glide performance.

Thanks for all the various suggestions. It convinces me there is not
any one procedure past what the POH says about getting the motor
started again and then technique becomes the rule.

Ed (N119NC)

On Mon, 12 Apr 2004 16:21:39 -0700, "C J Campbell"
wrote:


"Ed" wrote in message
.. .
I'm fairly new to GA after a 19 year break flying jets. I routinely
fly a single engine experimental with a constant speed prop mounted on
a Lycoming IO-360.

2 QUESTIONS:

1. What's the proper setup to simulate the way the plane would glide
in case of an engine failure? I'm looking for pitch and possibly a
manifold pressure number here.

Unfortunately, it will be with the engine at idle at flat pitch. I will
explain why below.


2. It that motor quits, will it still rotate through the flying
airspeed envelope or can I expect it to stop rotation (assuming it's
not frozen due to a mechanical failure)?

In idle, with the prop at flat pitch, it feels too draggy and comes
down like a rock. With it at high pitch, it seems to have too
optimistic a glide ratio. What's the happy medium?


The prop pitch is maintained by oil pressure. Most single engine piston
installations set up the constant speed prop so that it will go to flat
pitch if oil pressure is lost (the exact opposite of turboprops and piston
twins). This is supposed to maximize your chances of restarting the engine,
but you pay for it with glide range. The propeller will continue to windmill
and create a lot of drag, but with the engine out you have little choice --
your oil pressure will be zero. It makes sense when you consider that most
'engine failures' are caused by fuel mismanagement. All you have to do is
switch tanks and with the windmilling prop your engine will start right up
again. You can make the propeller quit rotating by flying very slowly, but
that will not improve your glide.

Turboprops and piston twins set the prop to feather if oil pressure is lost.
These propellers will stop rotating almost immediately.

I don't live near a dry lake bed or I'd just shut it down and find
out. I have the proper airspeeds for max range and min sink out of
the POH but it does not quote any type of glide ratio.

You could just stay in the pattern and shut it down. It should start right
up again just by giving it some fuel.

In article . net, Dave S wrote:
One caveat.. this works fine as long as the prop continues to windmill..
if it DOESNT... they you have just turned a training situation into what
may be a bonafide emergency.

I believe Highflyer has a story about that in a Taylorcraft...which
lacked an electric starter, and the prop had stopped turning. Slope
soaring saved the day.

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

On Tue, 13 Apr 2004 05:49:10 GMT, "Roy Epperson"
wrote:

With our Mooney F model at best glide speed when I pull the prop control all
the way back (max pitch), it saves me about 300 fpm while maintaining best
glide. With a minimum pitch, the blades are one big braking force.

I'll gladly take your collective word for it from in-flight
observations.

Mine were limited to shoving the prop ahead turning final (in every
complex aircraft I've ever flown in) at approx 1200-1400 rpm (prop
control previously set to 2300 in cruise) with no change in engine
rpm/prop noise noted.

Have pulled mis-rigged PT6A props to "flat" on short final a couple of
times, have the stained shorts to prove it.

Before I posted, I called my gov shop buddy to make sure his views
coincided with what I remembered from hanging around in his shop. He
related same, that the gov bench doesn't indicate useable gov pressure
until around 1500-1600 rpm. As I recall, on most engines, the gov
drive turns at about 90% of the indicated rpm.

I stuff I work on now has a fixed-pitch first stage "prop", and I
ain't allowed to drive it, so I can't add anything further.

Regards;

TC

wrote in message
...
Mine were limited to shoving the prop ahead turning final (in every
complex aircraft I've ever flown in) at approx 1200-1400 rpm (prop
control previously set to 2300 in cruise) with no change in engine
rpm/prop noise noted.

That's a completely different situation. At that power setting, the engine
didn't have enough power to drive the prop at the selected RPM (2300), and
so the blades were already at flat pitch. Selecting high RPM would have had
no effect, since the governor was already trying to increase RPM, to its
limits (maximum flat pitch).

Next time, pull the prop to *minimum* RPM and see your glide angle decrease.

Have pulled mis-rigged PT6A props to "flat" on short final a couple of
times, have the stained shorts to prove it.

Not sure how that statement fits in to the discussion, but the PT6 governors
work differently from those found on most piston-engine singles.

Before I posted, I called my gov shop buddy to make sure his views
coincided with what I remembered from hanging around in his shop. He
related same, that the gov bench doesn't indicate useable gov pressure
until around 1500-1600 rpm.

You mentioned "gov pressure" in an earlier post, and I still don't
understand what you mean. The force to change the prop blade angle comes
from springs and oil pressure, not the governor itself. All the governor
does is adjust oil valves to control how the oil moves through the pitch
change mechanism.

In any case, as with the others, I've had no trouble at all reducing the
blade pitch even in low-RPM, idle-power situations. I have no reason to
expect I'd have any trouble in an actual engine failure, assuming the engine
continued to windmill and run the oil pump.

Pete

On Tue, 13 Apr 2004 16:15:11 -0700, "Peter Duniho"
wrote:

snip

Next time, pull the prop to *minimum* RPM and see your glide angle decrease.

It'll likely be years, I don't do GA anymore.

Have pulled mis-rigged PT6A props to "flat" on short final a couple of
times, have the stained shorts to prove it.

Not sure how that statement fits in to the discussion, but the PT6 governors
work differently from those found on most piston-engine singles.

Doesn't have anything to do with it, this is Usenet. You really owe to
yourself to try it once, though. It's similiar to tromping on a
non-ABS brake pedal at 40 mph. Gets your attention at 75 feet AGL with
the nose down coming-over-the-fence.

Before I posted, I called my gov shop buddy to make sure his views
coincided with what I remembered from hanging around in his shop. He
related same, that the gov bench doesn't indicate useable gov pressure
until around 1500-1600 rpm.

You mentioned "gov pressure" in an earlier post, and I still don't
understand what you mean. The force to change the prop blade angle comes
from springs and oil pressure, not the governor itself. All the governor
does is adjust oil valves to control how the oil moves through the pitch
change mechanism.

The base of a governor is another oil pump, stepping up engine oil
pressure to over 175 psi. Maximum pressure is limited by a
spring-loaded pop-off valve, just like the engine oil pump.

http://www.mccauley.textron.com/prop...g03govern.html

was the best picture I could find of it in a 30 second Google.

In any case, as with the others, I've had no trouble at all reducing the
blade pitch even in low-RPM, idle-power situations. I have no reason to
expect I'd have any trouble in an actual engine failure, assuming the engine
continued to windmill and run the oil pump.

Agreed, like I indicated in another post, the oil pump/governor
doesn't care what's turning it.

TC

wrote in message
...
Not sure how that statement fits in to the discussion, but the PT6
governors
work differently from those found on most piston-engine singles.

Doesn't have anything to do with it, this is Usenet.

Okay...just thought I'd ask.

The base of a governor is another oil pump, stepping up engine oil
pressure to over 175 psi. Maximum pressure is limited by a
spring-loaded pop-off valve, just like the engine oil pump.

Yes, but as far as I know, that pump will work just as well as the engine
pump. Also, even if for some reason that pump failed, my understanding is
that it would simply reduce the responsiveness of the governor. It wouldn't
cause it to stop working altogether. The engine-supplied oil pressure would
be sufficient.

Agreed, like I indicated in another post, the oil pump/governor
doesn't care what's turning it.

Well, color me confused then. I thought we started this thread with you
suggesting that if the engine has failed, resulting in low RPM, you wouldn't
be able to get the prop to the coarse pitch setting.

But, if you agree with what I said, so much the better.

Pete

"Peter Duniho" wrote in message ...
wrote in message
...
Not sure how that statement fits in to the discussion, but the PT6
governors
work differently from those found on most piston-engine singles.

Doesn't have anything to do with it, this is Usenet.

Okay...just thought I'd ask.

Not a problem.

The base of a governor is another oil pump, stepping up engine oil
pressure to over 175 psi. Maximum pressure is limited by a
spring-loaded pop-off valve, just like the engine oil pump.

Yes, but as far as I know, that pump will work just as well as the engine
pump. Also, even if for some reason that pump failed, my understanding is
that it would simply reduce the responsiveness of the governor. It wouldn't
cause it to stop working altogether. The engine-supplied oil pressure would
be sufficient.

I really would like to spend 24 hours in your world. Having spent 20+
years living in aviation, I'm still learning. IMHO it becomes quite
obvious from reading your posts that airplane ownership has somehow
mysteriously given you insight that mere mortals such as myself are
sorely lacking.

Where did you obtain the basis for this theory? I somehow doubt that
you've ever had to troubleshoot/repair a prop/governor gripe. If you
had, and had done your homework, you would have learned that one of
the first steps in troubleshooting is verifying adequate oil pressure
(also a crude method of determining adequate oil volume) to the prop
governor. Please bear in mind, in a lot of engine designs, the prop
governor is located at the tail end of the oil system, with a lot of
built-in leaks between the engine oil pump and the governor pad.

I find it rather funny that while the prop/governor will not function
properly without approximately 30-40 psi to "step-up" to over 175 psi,
you have determined that the governor oil pump (which initially you
apparently doubted even existed) is not a necessary piece of the
puzzle.

Speaking from direct observation, at higher power settings,
reduced/insufficient governor pressure delivered to the propeller dome
can limit the ability to reduce engine rpm in a pressure-to-increase
pitch system, and failure to obtain maximum rpm in a
pressure-to-decrease system.

Again, from direct observation, this can be caused by insufficient oil
supply to the gov pad (see above), excessive rotor-to-housing
clearance/physical gov oil pump damage, a fault in the oil pressure
relief valve, or in extreme cases, excessive clearances/oil loss
between the main crankshaft bearing and the crankshaft.

Agreed, like I indicated in another post, the oil pump/governor
doesn't care what's turning it.

Well, color me confused then. I thought we started this thread with you
suggesting that if the engine has failed, resulting in low RPM, you wouldn't
be able to get the prop to the coarse pitch setting.

That's entirely correct. I described my personal experiences
in-flight, related that they were somewhat limited to the subject, and
that I needed clarification. I also contacted two professional GA
pilots, and a guy that has been repairing/overhauling prop governors
for 20 years prior to posting.

After reading subsequent replies, I freely admitted that I was wrong.
Now I can factor that information into my personal database for future
reference. Seeking new knowledge/other experiences was one of the
primary reasons I climbed into the stinking swamp of GA on the
internet to begin with.

The other primary reason was to share my experiences and knowledge
with no intention of financial gain. Over the years in these forums,
my chosen profession has been repeatedly attacked, my personal
experience and intent questioned.

After spirited credentialled discourse with apparently clueless twits,
surprisingly enuff I began to receive private communications from
lurkers (and posters) who wanted me to maintain their aircraft. As
this was never my intention, I had to become the anonymous
self-proclaimed hairy mole on the ass that is rec.aviation.

You see, I learned a long, long time ago that arguing on the Internet
is like getting a gold medal in the Special Olympics. You (figure of
speech, by no means a personal attack)may have "won", but you (along
with all the other contestants) are still mentally-challenged.

But, if you agree with what I said, so much the better.

I share your joy;

TC