Engine Failure

E

EnRoute

New Member
Hey all. I fly a C-182 and C-206 for a local skydive outfit. We fly our airplanes a little unconventionally, on the edge, and certainly by the seat of our pants. Upon dropping our load, I pull the prop RPM out all the way and bomb down from altitude gradually reducing my MP as I go. Often times when hi on short final, I will push my prop in as it acts as a speed brake, otherwise will land with the prop still out (low RPM)
My question is this. In looking at the POH, under emergency procedures, engine failures to be specific, I would have expected to see a reduction of RPM to increase my glide distance. I did not however. Why is this? I suppose the only logical answer would be that once the engine quits, one is unable to move the prop.?? If this is the case, it would seem that if you have any warning while the engine is still running/sputtering, I would want to pull my RPM back as far as I could.
Anybody....Anybody....:bandit:
 
EnRoute said:
I would have expected to see a reduction of RPM to increase my glide distance. I did not however. Why is this? I suppose the only logical answer would be that once the engine quits, one is unable to move the prop.??
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Whether or not not you'd be able to move the prop depends on exactly how the engine failed. Regardless, Part 23 requires that the glide ratio be calculated with the prop at the minimum drag position. For the C182, I haven't seen a whole lot of difference between low pitch/high pitch for my glide ratio. Arrow, different story.
 
EnRoute said:
If this is the case, it would seem that if you have any warning while the engine is still running/sputtering, I would want to pull my RPM back as far as I could.
Anybody....Anybody....:bandit:
Click to expand...

Cue the shock cooling/running over square debate in 3...2...1...

Seriously though, I think your odds of restarting the engine are better at a high RPM setting (the prop is taking less 'bite' and easier for the wind to turn).

We typically try for high airspeed with a steep bank at moderate power to lose altitude after releasing gliders, which is similar to what jump planes do (up and down all day long).

I would guess your skydive operation has some type of SOP???
 
I would think it would be in there too, but you answered your own question.

With a single engine airplane the prop has springs driving it towards fine/low pitch and you use oil pressure to work against the springs to get a coarse/high pitch.

If the engine fails, you aren't going to have oil pressure so there's no way to move it to high pitch/low rpm unless you have a partial engine failure/loss of power, etc.

At least that's how I understand it.
 
TFaudree_ERAU said:
Why wouldn't you have oil pressure?
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I was thinking worse case scenario. Losing all of your oil, engine stops, no oil pressure.

Obviously as long as you keep the prop windmilling, you'll have a little oil pressure.

But if you have a catastrophic engine failure (engine seizes) and the prop isn't windmilling, you'll have no oil pressure, no?
 
N519AT said:
I was thinking worse case scenario. Losing all of your oil, engine stops, no oil pressure.

Obviously as long as you keep the prop windmilling, you'll have a little oil pressure.

But if you have a catastrophic engine failure (engine seizes) and the prop isn't windmilling, you'll have no oil pressure, no?
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I agree. I read your original comment to say that ALL "total" engine failures would result in zero oil pressure; total failure meaning the engine is no longer producing any power. There are so many different causes of a total engine failure, some of which will still allow the prop to windmill (fuel exhaustion/starvation for example).
 
N519AT said:
I was thinking worse case scenario. Losing all of your oil, engine stops, no oil pressure.

Obviously as long as you keep the prop windmilling, you'll have a little oil pressure.

But if you have a catastrophic engine failure (engine seizes) and the prop isn't windmilling, you'll have no oil pressure, no?
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If the engine seizes, do you really care what pitch the prop is in?
 
TFaudree_ERAU said:
I agree. I read your original comment to say that ALL "total" engine failures would result in zero oil pressure; total failure meaning the engine is no longer producing any power. There are so many different causes of a total engine failure, some of which will still allow the prop to windmill (fuel exhaustion/starvation for example).
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Ah, I see. I should have been more clear. After twelve hours of work on four hours of sleep, I'm lucky I'm even typing comprehensible sentences. :)

If the engine seizes, do you really care what pitch the prop is in?
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Well, obviously not, but I was just taking it to the extreme.
 
drunkenbeagle said:
As long as the prop is turning, there should be at least some oil pressure.
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But will it be enough oil pressure to fight against the spring?

Basically what all our mechanics have told me was, "well when you get your engine failure, pull the prop and report back." :cwm27:
 
Douglas said:
But will it be enough oil pressure to fight against the spring?

Basically what all our mechanics have told me was, "well when you get your engine failure, pull the prop and report back." :cwm27:
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That is what i was thinking. Not to mention the prop would kinda cycle between low and high pitches since it would slow down when put into a high pitch and then speed up at a lower pitch. Probably would find a happy medium realistically.
 
N18040 said:
If the engine seizes, do you really care what pitch the prop is in?
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Why yes, I really do care what position the prop is in when the engine seizes. I'd much rather have it seize in the min drag configuration but I also like pretty flowers and sunshine. Maybe I'm just optimistic.
 
Codyjp said:
Why yes, I really do care what position the prop is in when the engine seizes. I'd much rather have it seize in the min drag configuration
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A stopped prop is a pretty low drag configuration and it doesn't appear to be affected much by changes in blade angle. There is a schematic in Aerodynamics for Naval Aviators on page 149 that shows the drag on a stopped prop remains fairly constant until past the 30 degree position. The max blade angle on a C182 is 31 degrees. Remember that the drag on a windmilling prop is due to the reverse thrust being created, not the angle per se.

The drag for a windmilling prop is much, much higher for low blade angles, but drops rapidly with lower RPM (increased blade angles). The drag drops below that of the stopped prop once the blade angle increases past the 20 degree point.
 
tgrayson said:
A stopped prop is a pretty low drag configuration and it doesn't appear to be affected much by changes in blade angle. There is a schematic in Aerodynamics for Naval Aviators on page 149 that shows the drag on a stopped prop remains fairly constant until past the 30 degree position. The max blade angle on a C182 is 31 degrees. Remember that the drag on a windmilling prop is due to the reverse thrust being created, not the angle per se.

The drag for a windmilling prop is much, much higher for low blade angles, but drops rapidly with lower RPM (increased blade angles). The drag drops below that of the stopped prop once the blade angle increases past the 20 degree point.
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Please tell me you checked the page number and that you didn't have it memorized.
 
N519AT said:
With a single engine airplane the prop has springs driving it towards fine/low pitch and you use oil pressure to work against the springs to get a coarse/high pitch.
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Many cases and in the case of the OP this is true. Some SE airplanes- such as aerobatic airplanes- go to course pitch in the case of an engine failure. Next time you see an aerobatic airplane with a CS prop on the ramp look close at the prop position.
 
Blackhawk said:
Many cases and in the case of the OP this is true. Some SE airplanes- such as aerobatic airplanes- go to course pitch in the case of an engine failure. Next time you see an aerobatic airplane with a CS prop on the ramp look close at the prop position.
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