Seneca Propeller Feathering

[bLizZuE]

At cruise power, in cruise flight. An engine experiences a loss of oil pressure.

Will the oil loss send the propeller into the high-pitch, low RPM, or feathered condition? Will the propeller reach 800 RPMs and activate the anti-feathering pins? Considering at a 75% cruise power setting, the RPM is somewhere between 2400-2600 RPM.

This has been a pretty one sided debate, however I'm interested to hear the collective opinion.

[TFaudree_ERAU]

No. It would go to a fine pitch, high rpm position. What you are describing is an auto-feather system. The Seneca does not have such a system.

[minitour]

Originally Posted by TFaudree_ERAU

No. It would go to a fine pitch, high rpm position.

What?

When I flew the Seneca II, it was like any other piston twin I have flown. Oil pressure forces the prop to a high rpm position, removing that oil pressure allows the prop to go to a low RPM position.

The piston singles that I've flown function the way you describe. Loss of oil pressure forces the prop to high RPM.

Would the prop feather itself? I don't believe so. Then again, I don't really think it would go below about 1000 RPM either.

-mini

[juxtapilot]

Originally Posted by TFaudree_ERAU

No. It would go to a fine pitch, high rpm position. What you are describing is an auto-feather system. The Seneca does not have such a system.

Huh?

Originally Posted by minitour

What?

When I flew the Seneca II, it was like any other piston twin I have flown. Oil pressure forces the prop to a high rpm position, removing that oil pressure allows the prop to go to a low RPM position.

The piston singles that I've flown function the way you describe. Loss of oil pressure forces the prop to high RPM.

Would the prop feather itself? I don't believe so. Then again, I don't really think it would go below about 1000 RPM either.

-mini

The loss in oil pressure will move the prop into low pitch, (maybe feathered?) condition. The propeller will move past the 850 RPM stop because during flight you will be at a higher RPM.

[esa17]

Directly from the Seneca I POH:


Not a whole lot room for debate.

[TFaudree_ERAU]

Originally Posted by minitour

What?

When I flew the Seneca II, it was like any other piston twin I have flown. Oil pressure forces the prop to a high rpm position, removing that oil pressure allows the prop to go to a low RPM position.

The piston singles that I've flown function the way you describe. Loss of oil pressure forces the prop to high RPM.

Would the prop feather itself? I don't believe so. Then again, I don't really think it would go below about 1000 RPM either.

-mini

You're right. Brain fart. I was going down the road of "feathering". In my mind, feathering is what a King Air prop does when you shut it down. Simply going to a low RPM pitch does not constitute "feathering" in my opinion. It won't feather until you pull the big blue knob back.

[matt152]

Read the POH excerpt. Oil pressure is the only thing that keeps it from feathering. You don't have to pull the blue handle back if oil pressure is already lost. It will feather if you lose oil pressure.

[minitour]

Originally Posted by matt152

Read the POH excerpt. Oil pressure is the only thing that keeps it from feathering. You don't have to pull the blue handle back if oil pressure is already lost. It will feather if you lose oil pressure.

Do you have something other than what was posted above? The image from the book that is posted above reads that nitrogen pushes the prop toward the feather or low RPM position...not into feather. The word "toward" makes a big difference.

-mini

[matt152]

Originally Posted by minitour

Do you have something other than what was posted above? The image from the book that is posted above reads that nitrogen pushes the prop toward the feather or low RPM position...not into feather. The word "toward" makes a big difference.

-mini

What would keep it from being pushed to feather other than a loss of oil pressure? The oil pressure is acting against the nitrogen charge. The only thing is the feathering lock provided the prop is below 800.

It also says oil pressure sends the prop "toward" high RPM.

[matt152]

Airplane Flying Handbook, page 12-3:

"In contrast, the constant-speed propellers installed

on most multiengine airplanes are full feathering,
counterweighted, oil-pressure-to-decrease-pitch
designs. In this design, increased oil pressure from the
propeller governor drives the blade angle towards low
pitch, high r.p.m.—away from the feather blade angle.
In effect, the only thing that keeps these propellers
from feathering is a constant supply of high pressure
engine oil. This is a necessity to enable propeller feathering
in the event of a loss of oil pressure or a propeller

governor failure."

[TFaudree_ERAU]

Go fly a Seneca and pull the left engine mixture to idle cut off just as you climb through 50" AGL. Don't touch the prop lever.

Report back and let us know if that prop feathers.

[TFaudree_ERAU]

http://ntsb.gov/ntsb/brief.asp?ev_id...14X38942&key=1

Things to note:
1) Pilot shut off the mags by mistake
2) Prop did not feather on it's own

http://ntsb.gov/ntsb/brief.asp?ev_id...04X00062&key=1

Things to note
1) Right engine failed for unknown reasons
2) Prop did not feather on it's own
3) Aircraft landed short of runway
4) Pilot faulted for not following checklist, including feathering prop on inoperative engine
Why would a pilot be faulted for not feathering the prop if it was supposed to do it itself?

[matt152]

If the prop is windmilling, the engine is turning, the oil pump is still pumping. Oil pressure will stay up.

If you have a loss of oil pressure, i.e. oil pump failure, or total loss of oil, it should feather. The thing is designed to do this.

There was no loss of oil pressure in either of the cases you cited.

Just because the mixture is pulled does not mean you lose oil pressure if the prop is windmilling. You have to lose oil pressure for some other reason.

[esa17]

Originally Posted by TFaudree_ERAU

Things to note
1) Right engine failed for unknown reasons
2) Prop did not feather on it's own
3) Aircraft landed short of runway
4) Pilot faulted for not following checklist, including feathering prop on inoperative engine
Why would a pilot be faulted for not feathering the prop if it was supposed to do it itself?

The prop will automatically retard to the point just above the feather locking position when oil pressure is lost (approx 850rpm) but they do require pilot input to totally feather.

The most violent part of the engine shutdown above was the actual feathering because there was no oil pressure resisting the nitrogen. When I feathered the engine it yawed violently but make no mistake the engine was NOT at fine pitch. It was at a very low pitch.

[bLizZuE]

Originally Posted by TFaudree_ERAU

Go fly a Seneca and pull the left engine mixture to idle cut off just as you climb through 50" AGL. Don't touch the prop lever.

Report back and let us know if that prop feathers.

This is not the scenario in question.

[matt152]

Originally Posted by esa17

The prop will automatically retard to the point just above the feather locking position when oil pressure is lost (approx 850rpm) but they do require pilot input to totally feather.

I am not sure what these pictures are illustrating. How did you simulate a loss of oil pressure?

[bLizZuE]

I'm guessing by all the oil running off the engine nacelle, that it wasn't simulated.

[matt152]

Jeez, I didn't even see that. Was pressure completely lost? Well, I guess experience has spoken.

What aircraft was that?

[esa17]

Originally Posted by matt152

I am not sure what these pictures are illustrating. How did you simulate a loss of oil pressure?

By blowing two softball sized holes in the engine case:


I'm a very through instructor.

[matt152]

Originally Posted by esa17

By blowing two softball sized holes in the engine case: I'm a very through instructor.

[Inverted]

Originally Posted by matt152

If the prop is windmilling, the engine is turning, the oil pump is still pumping. Oil pressure will stay up.

Not if oil pressure loss was the issue to begin with.

I am doing my multi add on as we speak flying a Seneca. When we dump an engine on purpose by shutting fuel down, oil pressure loss is a direct result, it might not go to zero but a windmilling engine wont be producing large quantities of pressure. It does NOT auto feather. you have to physically pull it back into feather. Whether its nitro or there still needs to be enough oil pressure to feather I do not know because I havent read the POH in depth quite yet.

[matt152]

Originally Posted by Inverted

Not if oil pressure loss was the issue to begin with.

I know. This was the point of the OP. Killing the engine with the fuel selector or mixture is different from a running engine that experiences a loss of oil pressure.

[shdw]

Originally Posted by esa17

By blowing two softball sized holes in the engine case:
I'm a very through instructor.

Did you do that with a 12 gauge or pre planted explosives?

[esa17]

Originally Posted by shdw

Did you do that with a 12 gauge or pre planted explosives?

Two words:
Underpants Gnomes. Turns out phase 2 is destroying engines.

[minitour]

Originally Posted by esa17

The prop will automatically retard to the point just above the feather locking position when oil pressure is lost (approx 850rpm) but they do require pilot input to totally feather.

I'll defer to the guy that's actually experienced it. Everyone else can decide for themselves.

-mini