CS prop and engine out procedure?

[mchesney]

Let me preface this by informing you that I'm a relatively new pilot and under 100 hrs. I recently bought into a shared ownership of a '70 177b... Love the plane! It has a CS prop which I'm getting comfortable with but was wondering what the best position would be for an engine out forced landing. The checklist and poh do not address this that I have found.

 

[Funkeruski]

I doubt you can adjust it if the engine is out.

 

[zaitcev]

My instructor said that at least on 200 hp Lycoming there's a gas accumulator that creates fake oil pressure just in such a case.

Edit: I went to look in section 4 of actual manual and it says: "At best gliding angle, with the engine windmilling, and the propeller control in full "decrease RPM," the aircraft will travel approximately 1.6 miles for each thousand feet of altitude". So the good people at Vero Beach seem to presume that windmilling creates enough oil pressure.

 

[timwinters]

I doubt you can adjust it if the engine is out.

Sure you can if a loss of oil wasn't the cause of the failure. At least that's the case in my 182. Engine out, prop windmilling, (for real, not pretend, BTDT), pull the prop and it's like getting kicked in the butt.

 

[jpower]

I'm not sure how the mechanics of it work (whether you'd be able to adjust it slowly with whatever you get out of the windmilling?), but assuming you could, I would think you'd want to adjust it to be in a low RPM setting. That positions the blades so they are more aligned with the airflow, meaning that there will be less drag.

I just got checked out in a 172 with what I've been told is an aggressive cruise prop, and that thing floats like none other. There aren't any other differences between it and any other 172 that I know of, so I assume (and the CFI tells me) that it's the prop.

Also, thinking about it, you'd want it in the low RPM setting, because that means that the air passing over the propeller has to do less work on the propeller, and the more air that tries to spin the propeller, the slower you'll go.

Edit: looks like other people who seem to know more what they're talking about posted while I had forgotten to hit "submit". Oops!

 

[skidoo]

For and experiment, is it safe to the engine to climb to say 6000 ft over the airport, pull the throttle and mixture to kill any power, establish best glide, determine the fpm loss rate, and then pull the prop to low rpm and note the change in fpm loss, then re-establish mixture and throttle?

 

[Tony_Scarpelli]

yes, you should know that as well as how many feet it takes to do a tear drop 180 d turn. My CFI had me do this in my Cherokee.

 

[ChitDisturber]

In most single engine pistons the prop will fail (as in loss of oil pressure, for whatever reason) forward/high rpm.

You need oil pressure on most SEP planes to overcome the centrifugal weights that pull it forward.

 

[kgruber]

For and experiment, is it safe to the engine to climb to say 6000 ft over the airport, pull the throttle and mixture to kill any power, establish best glide, determine the fpm loss rate, and then pull the prop to low rpm and note the change in fpm loss, then re-establish mixture and throttle?

You "could" do that. But it would be safer to leave the engine running. Forget pulling the mixture.

 

[ChitDisturber]

You "could" do that. But it would be safer to leave the engine running. Forget pulling the mixture.

It will be generating more oil pres running, thus nonrealistic on a running engine. I wouldnt really want to ICO it ether, especially with only 100tt

 

[hindsight2020]

You "could" do that. But it would be safer to leave the engine running. Forget pulling the mixture.

But that invalidates the test because the oil pressure created by combustion power, even idle, is substantial compared to that being created when the engine is merely windmilling under no combustion.

This is to do about nothing, one can probably safely assume you will NOT have enough oil pressure being created by the engine when dead and windmilling, to have any impact in the effort to counteract the spring that forces these propeller installations towards the high RPM position.
This is in contrast to turbine installations, where the propellers are sprung opposite to this. I.e they fail towards the feather position.

 

[MAKG1]

It's RPM alone that makes oil pressure. It doesn't matter whether combustion makes it spin or slipstream or Goonies or whatever. Just about every oil pump is mechanically driven either directly or indirectly to the crankshaft.

 

[poadeleted20]

My instructor said that at least on 200 hp Lycoming there's a gas accumulator that creates fake oil pressure just in such a case.

Good thing you went to the book to learn the truth.

Edit: I went to look in section 4 of actual manual and it says: "At best gliding angle, with the engine windmilling, and the propeller control in full "decrease RPM," the aircraft will travel approximately 1.6 miles for each thousand feet of altitude". So the good people at Vero Beach seem to presume that windmilling creates enough oil pressure.

That is correct, and typical of what to do with a c/s prop on a single engine airplane if the engine quits.

Of course, if you lose oil pressure, the prop is going to the low pitch stops (full high RPM/max drag) whether the engine is running or not, thanks to the lack of oil pressure to balance the force of the counterweights and precharge. This is the reverse of how twins are rigged (where the prop goes feathered if you lose oil pressure), but that's another story.

 

[poadeleted20]

For and experiment, is it safe to the engine to climb to say 6000 ft over the airport, pull the throttle and mixture to kill any power, establish best glide, determine the fpm loss rate, and then pull the prop to low rpm and note the change in fpm loss, then re-establish mixture and throttle?

It won't hurt the engine (at least, not as long as you don't screw it up and plant the airplane nose first in the dirt), but in the FAA's opinion, and in mine, it's not an acceptable training/testing practice (at least in singles). Some folks do it anyway, and every year there are a few accident reports when someone did that, screwed up the approach, and then couldn't get a restart fast enough. Choose wisely.

 

[kgruber]

But that invalidates the test because the oil pressure created by combustion power, even idle, is substantial compared to that being created when the engine is merely windmilling under no combustion.

This is to do about nothing, one can probably safely assume you will NOT have enough oil pressure being created by the engine when dead and windmilling, to have any impact in the effort to counteract the spring that forces these propeller installations towards the high RPM position.
This is in contrast to turbine installations, where the propellers are sprung opposite to this. I.e they fail towards the feather position.

I guess you didn't read his question. He asked if it were "safe." The answer is still no.

And not all turbine props automatically fail to feather.

 

[Tom-D]

When the engine quits fly the aircraft and forget the prop, fly the aircraft, the difference gained or lost, between full high blade angle and the lowest blade angle can be measured in inches.

The theory is good but in reality you are better off concentrating on air speed management, setting up the approach, and ensuring you and your pax can walk away from the accident site. Fidding with a prop knob is a waist of time, when time matters.

 

[Fearless Tower]

My thought on engine failure in a single is this: depending on the cause of the failure, you may or may not have the oil pressure to adjust the prop. So, from a training standpoint, I would train for the worst case (flat pitch- most drag). If you can put the plane where you want it in that condition, you will have the greatest chances for a successful outcome.

 

[Fearless Tower]

The theory is good but in reality you are better off concentrating on air speed management, setting up the approach, and ensuring you and your pax can walk away from the accident site. Fidding with a prop knob is a waist of time, when time matters.

Exactly.

 

[timwinters]

While we're on the topic of engine outs...

A "properly rigged" C152, 172, 182 will settle in very close to "best glide" when the trim is rolled full aft.

I was told about 10 years ago when I toured the Cessna plant in Independence, KS. This method worked on my 172 and it works on my 182.

I know people it doesn't work for. My only explanation..."properly rigged"...though I really have no idea why.

Test it on yours. If it works, it certainly saves A LOT of time when cockpit stress is high during an emergency. Just roll trim all the way back and go on to the next task.

 

[ronnieh]

Um, hindsight, the combustion has nothing to with oil pressure. It is proportional to crankshaft RPM.
And let me get this straight on the turbines. Just as the gear is coming up the fire goes out, you think the prop will feather (unless equipped with auto feather)? Really?

 

[coma24]

I've done these tests at idle with the Lancair and the difference in glide ratio is a lot more than trivial.

When my engine failed at 3000ft in IMC last year, I had the prop pulled back within a couple of seconds of it occurring. It sure wasn't "fiddling" or a waste of time. It reduced my rate of descent and bought me time. In a 200kt airplane, the difference between being engine out with prop full forward, and prop full back is like the difference between being on the freeway and shifting to neutral (prop back), or being in neutral and lightly applying the brake (prop forward). It's significant.

The only reason I pulled it back is because I've practiced it maybe 10-12 times in the pattern since I bought the plane, where my SOP for engine out practice is to pull the prop all the way back. You can fly an almost standard pattern from abeam the numbers (especially if you were at all fast on the downwind). Only once landing is more than assured do I start easing the prop forward, along with gear, flaps, etc. Then it becomes a veritable brick.

 

[Immelman]

If you're still getting oil pressure after the failure... ABSOLUTELY it makes a difference. In my mooney its a 30-40% reduction in sink rate. You can see your glide extend as the nose comes UP to maintain glide speed as the prop comes back to high pitch. I would absolutely suggest doing an experiment, maintaining best glide speed at idle power and noting the difference in sink rate and landing options with the prop at high vs low pitch.

Now would I go about all engine out practice this way? No. You don't know how your enigne will fail. Will things just sieze up? Will oil be lost? Who knows! I advocate practicing your power-off approaches and landings with the prop full forward for this reason. You'll train yourself for a more 'worst case' glide distance this way, which can be useful as you get closer to your landing spot. With that said, I think that pulling the prop to high pitch a very valuable tool in your gliding toolbox that just might help you make a better landing site should the unthinkable happen, and you do have sufficient oil pressure to control the prop.

 

[Tom-D]

I wonder if anyone has noticed that what happens to the prop will depend upon what prop / engine combination your dealing with?

What is CTM and how does that effect the blades when there is no controlling oil pressure?

How many single engine aircraft built under a production certificate has an accumulator to push the blade angle in either direction?

what happens when an old beech roby C/S prop do when it looses oil pressure?

 

[poadeleted20]

When the engine quits fly the aircraft and forget the prop, fly the aircraft, the difference gained or lost, between full high blade angle and the lowest blade angle can be measured in inches.

Inches of pitch, perhaps, but not glide range. The difference between max high and max low pitch is significant (on the order of 10%, IIRC), and it doesn't take half a second to pull that prop control full aft. Further, if oil pressure is lost, that's where it's going anyway in a piston single, thanks to centrifugal force/counterweights, etc., just like the props on twins are built to go feathered if oil pressure is lost.

 

[Tom-D]

Inches of pitch, perhaps, but not glide range. The difference between max high and max low pitch is significant (on the order of 10%, IIRC), and it doesn't take half a second to pull that prop control full aft. Further, if oil pressure is lost, that's where it's going anyway in a piston single, thanks to centrifugal force/counterweights, etc., just like the props on twins are built to go feathered if oil pressure is lost.

That may or may not be a good theory dependent upon where the governor valve is positioned and if the engine is rotating or not.

It is already on the low pitch stops and the engine is not rotating it isn't going any where, no matter what you do with the knob.

 

[MAKG1]

And what penalty do you suffer by pulling the prop in the unlikely event it stopped? Half a second in the engine out flow? You'll lose a lot more in the WTF period.

Pull the prop every time. It will either help or do nothing. On the other hand, indecision about whether to do it or not can be more significant.

 

[Sac Arrow]

Inches of pitch, perhaps, but not glide range. The difference between max high and max low pitch is significant (on the order of 10%, IIRC), and it doesn't take half a second to pull that prop control full aft. Further, if oil pressure is lost, that's where it's going anyway in a piston single, thanks to centrifugal force/counterweights, etc., just like the props on twins are built to go feathered if oil pressure is lost.

That may or may not be a good theory dependent upon where the governor valve is positioned and if the engine is rotating or not.

It is already on the low pitch stops and the engine is not rotating it isn't going any where, no matter what you do with the knob.

I think the real question is, do you get more range from a windmilling prop set to maximum pitch and so able to govern itself, or a stopped prop? I suppose the aircraft manufacturers (Piper Arrow in my case at least) have decided it's the former, as it's in my POH as well.

 

[Dan Thomas]

I think the real question is, do you get more range from a windmilling prop set to maximum pitch and so able to govern itself, or a stopped prop? I suppose the aircraft manufacturers (Piper Arrow in my case at least) have decided it's the former, as it's in my POH as well.

Getting the prop stopped takes time and altitude. The only time I ever stopped a prop deliberately (in flight) was in a 150, and I had the nose well up and the airspeed just above the stall before it finally stopped turning. If one had a true emergency, fooling around this way would cost more time than one can afford unless he's at a really big altitude, and it's also distracting.

So Piper doesn't suggest it. Nobody would unless feathering was an option.

Dan

 

[Sac Arrow]

Getting the prop stopped takes time and altitude. The only time I ever stopped a prop deliberately (in flight) was in a 150, and I had the nose well up and the airspeed just above the stall before it finally stopped turning. If one had a true emergency, fooling around this way would cost more time than one can afford unless he's at a really big altitude, and it's also distracting.

So Piper doesn't suggest it. Nobody would unless feathering was an option.

Dan

The Airplane Flying Handbook does....

 

[poadeleted20]

That may or may not be a good theory

It's not just theory -- it's engineering and physical laws fact.

dependent upon where the governor valve is positioned and if the engine is rotating or not.

Yes, if the engine fails catastrophically so the prop is frozen, that's another story, but of course in that case you don't have much choice about the matter. We're discussing what to do if you have the choice, and the choice is clear -- pull full aft for high pitch. If the situation is such that you can't control it, all you've wasted is about half a second, so it should still be procedure so you don't forget it in the vast majority of engine failure cases where it will help.

 

[poadeleted20]

I think the real question is, do you get more range from a windmilling prop set to maximum pitch and so able to govern itself, or a stopped prop? I suppose the aircraft manufacturers (Piper Arrow in my case at least) have decided it's the former, as it's in my POH as well.

Depends on your altitude at the time. Richard L. Collins wrote an article for Flying magazine some years back about trying this in a Cessna 182. He found that you lose a lot of altitude in the process of slowing to a low enough speed to cause the engine to stop windmilling and then dropping the nose to accelerate back to best glide speed. He discovered that in a C-182 above about 8000 AGL, the gain in glide range once the prop is stopped outweighs the loss during the process of stopping it, but below that altitude, you are better off leaving it windmilling at the max blade pitch/low RPM setting. This has been report by others repeating the experiment in other aircraft with very similar results.

 

[poadeleted20]

The Airplane Flying Handbook does....

A lot of others, too, when high enough, and well-supported in those circumstances by the available data. The altitude where it makes a difference in light singles appears to be somewhere around 7000-8000 AGL.

 

[Sac Arrow]

A lot of others, too, when high enough, and well-supported in those circumstances by the available data. The altitude where it makes a difference in light singles appears to be somewhere around 7000-8000 AGL.

Yes, but that wasn't the point I was making. I'm posing the question of whether you will get a better glide angle with a windmilling CS prop at full pitch vs a stopped prop.

 

[poadeleted20]

Yes, but that wasn't the point I was making. I'm posing the question of whether you will get a better glide angle with a windmilling CS prop at full pitch vs a stopped prop.

Stopped prop is better glide ratio once the prop is stopped.

 

[bbchien]

Tom D, and RBL are both right on this one.

If it's still windmilling when you have finished the list, put the prop lever in the low rpm position, you're not going to restart it any longer. But remember, the list includes all components of the diversion....new heading, selection of landing zone, etc. But you should not let this take longer than a few seconds.

TD's point is to do the divert and don't be flying AWAY from your field of intended landing, and to nail the airspeed. IF when you figure out where you're going, set up best glide and heading, and it's STILL windmilling, then pull the pitch control.

You do get a significantly longer horizontal glide with the pitch at coarse- but this is not significant compared to flying away from a perfectly good, reachable airport for a whole minute while you screw around, or screwing around a anything other tnan best glide.

The accident two summers ago in the Cessna 206 in lake Michigan, off Ludington, is a great example of a pilot who might have made it had he turned back at the FIRST sign of trouble, rather than after the last. He ditched 4 miles off Ludington and one of his party didn't make it. In the minute he hesitated, he lost 1000 (or a mile) and headed an additional two miles away, lengthening his flight path 4 whole miles.....

He might have made it to the beach.....

BTDT and walked away (Mooney M20), without any damage, early 90's, whole family aboard.

 

[poadeleted20]

That's all true, Bruce, but it's not an "either/or" situation. You can pull the prop back with one hand while turning the plane with the other so you don't go any farther away while increasing your glide range.

 

[bbchien]

Yup. That Alma ditch was a tragedy. If he had done EVERYTHING right, he had a chance.

Most GA single pilots, though, don't hack the "hot" moment so well. Like learning the hairpin turnback, if they haven't practiced recently, I'm rehearsing them from 2,000 feet rather than 1,000.....I'd like to live a few more decades.

I had an engineer ask me in the MIDDLE of a turnback drill, about the blue knob. The ball was out and the airspeed was slow, 45 degree banked turn, and I just shoved the yoke forward, stomped on the rudder and screamed at him, "LATER, fly the friggin bird!".

When we got down, I explained, "The prop is icing on the cake. Mostly you just want to eat cake, not dirt"

 

[dell30rb]

My thought on engine failure in a single is this: depending on the cause of the failure, you may or may not have the oil pressure to adjust the prop. So, from a training standpoint, I would train for the worst case (flat pitch- most drag). If you can put the plane where you want it in that condition, you will have the greatest chances for a successful outcome.

Agreed, and with more drag and a steeper approach, its easier to nail a power off landing

 

[Tom-D]

Yup. That Alma ditch was a tragedy. I he had done EVERYTHING right, he had a chance.

Most GA single pilots, though, don't hack the "hot" moment so well. Like learning the hairpin turnback, if they haven't practiced recently, I'm rehearsing them from 2,000 feet rather than 1,000.....I'd like to live a few more decades.

I had an engineer ask me in the MIDDLE of a turnback drill, about the blue knob. The ball was out and the airspeed was slow, 45 degree banked turn, and I just shoved the yoke forward, stomped on the rudder and screamed at him, "LATER, fly the friggin bird!".

When we got down, I explained, "The prop is icing on the cake. Mostly you just want to eat cake, not dirt"

I love it, gotta steal that for a signature line.

Does every one understand the " WHY " of pulling the prop back?

CTM= (Centrifugal twisting moment) occurs in every prop blade, it is by matter of design the blade is an airfoil, it has a center of lift just as every airfoil does. If that center of life is designed forward of the pivot point of the blade the CTM will force the blade up to the high bland angle producing a low RPM.

If that center of lift is behind the blade pivot point the CTM will force the blade to a lower blade angle and produce a high RPM.

Understanding that, we must also know that the normal control of the blade angle is done thru a hydraulic action caused by the engine oil pressure acting thru a propeller governor, using a slide and sleeve selector valve that will lock the propeller if the governor is not positioned in a propeller over speed condition which will open the passage of oil out of the piston/cylinder that moves the blade.

So, the bottom line here is this, it requires 2 actions to get the blade up to a high pitch position, Rotation of the engine to create CTM, and the opening of the Governor selector to allow oil to escape from the Prop.

 

[brcase]

A lot of others, too, when high enough, and well-supported in those circumstances by the available data. The altitude where it makes a difference in light singles appears to be somewhere around 7000-8000 AGL.

If you haven't practiced it in the airplane you are flying, don't try it in an emergency. Or at a minimum don't take more than about 20 seconds to try to stop it. Some airplanes it is nearly impossible to stop the prop in flight, and you better be proficent at slow flight.

If adding glide range or time will help, then pull the prop back it will significantly increase the glide ratio, if you don't have enough oil pressure to operate the prop then the engine probably isnt going to be turning very long anyway.
Some manufacturers recommend pulling the prop in an power failue emergency, Bellanca Viking is one I know of.

Brian