Seneca Propeller Feathering

matt152 said:
If the prop is windmilling, the engine is turning, the oil pump is still pumping. Oil pressure will stay up.
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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.
 
esa17 said:
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.
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I'll defer to the guy that's actually experienced it. Everyone else can decide for themselves.

-mini
 
esa17 said:
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.
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:yeahthat:

Loss of oil pressure is loss of oil pressure. It doesn't matter if you blow the cylinders out the sides of the cowls or simply just pull the mixture. The prop is only going to go so far (just above feather).

This whole scenario is very simple to test. What happens to the prop when you shut the engine down on the ramp? If a loss of oil pressure allowed the prop to feather, don't you think it would feather every time you shut it down?
 
ctab5060X said:
This whole scenario is very simple to test. What happens to the prop when you shut the engine down on the ramp? If a loss of oil pressure allowed the prop to feather, don't you think it would feather every time you shut it down?
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Of course not. The locks prevent it from doing so. Duh. :insane:

-mini
 
minitour said:
Of course not. The locks prevent it from doing so. Duh. :insane:

-mini
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Yeah, I know... but I am talking in terms of what the prop will do pitch wise with a loss of oil pressure. Unless something is broken, a prop is not going to feather without input... on the ground or in the air.

The only time I have had a prop to feather on shutdown was the night the guts of the prop hub decided to shatter and the locks failed to engage. Otherwise, every other time I have had to shut one down, I had to feather the prop.


I also agree with esa17... the most violent part is the actual feathering.
 
ctab5060X said:
Yeah, I know... but I am talking in terms of what the prop will do pitch wise with a loss of oil pressure. Unless something is broken, a prop is not going to feather without input... on the ground or in the air.
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Seneca POH, "Feathering Procedure":

Loss of centrifugal force due to slowing RPM will actuate a stop pin that keeps the propeller from feathering each time the engine is stopped on the ground.

The reason you pull the blue knob all the way back is to dump the oil pressure from the prop hub when you have an engine failure. The engine is still being turned by a windmilling prop which is providing oil pressure through the oil pump. If you have COMPLETELY lost oil pressure the prop should feather.

Or Maybe Piper got it wrong in the POH.
 
From the Hartzell propellers owner's manual:

If oil pressure is lost during operation, the propeller will feather. Feathering occurs because the air charge, spring, and blade counterweights are no longer opposed by hudraulic oil pressure. The air charge, spring and blade counterweights are then free to increase blade pitch to the feathering (high pitch) stop.

Normal in-flight feathering of these propellers is accomplished when the pilot retards the propeller pitch control past the feather detent. This allows control oil to drain from the cylinder and return to the engine sump. The engine can then be shut down.
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Inverted said:
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.
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Cutting fuel off to the engine causes insignificant loss of oil pressure, if any.

Keep in mind the ONLY force keeping the propeller FROM the feather position is oil pressure. Aerodynamic twisting force, counterweights, the nitrogen charge and spring all send the propeller TO the feather position. It is this reason that any significant or complete loss of oil pressure, the propeller will feather. Regardless of the position of the propeller lever. *edit- as long as engine RPM is above 800 or 950(depending on system) and the anti-feathering lock has not engaged.
 
matt152 said:
If you have COMPLETELY lost oil pressure the prop should feather.
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bLizZuE said:
THIS is the question.
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bLizZuE said:
It is this reason that any significant or complete loss of oil pressure, the propeller will feather. Regardless of the position of the propeller lever.
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So which one is it? Complete loss or significant loss? I'd say in the case of the 310, it was certainly significant and likely a complete loss. The prop didn't feather.

High pitch stop pins?
 
TFaudree_ERAU said:
So which one is it? Complete loss or significant loss? I'd say in the case of the 310, it was certainly significant and likely a complete loss. The prop didn't feather.
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I'm not convinced of that. You can have an oil leak and still have oil pressure.

That the prop did not feather suggests there WAS still oil pressure.
 
TFaudree_ERAU said:
So which one is it? Complete loss or significant loss? I'd say in the case of the 310, it was certainly significant and likely a complete loss. The prop didn't feather.

High pitch stop pins?
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To clarify, a significant loss of oil pressure will send the prop towards feather. A complete loss of oil pressure will completely feather the propeller.
 
matt152 said:
This is the feather position. I don't believe there is such a thing as "high pitch stop pins."
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From an NTSB report for a fatal accident in a BE58
The left engine's propeller cycled normally with shop air pressure from the start lock position to the low pitch stop position. The feathering spring moved the 3 blades into the feather position when the high speed stop was removed. The pitch-change cylinder was sectioned to expose its interior and associated components. The feathering spring was intact and unremarkable. The hard plastic or nylon spring retainer cup was sectioned. Indent and score or drag markings were observed on its interior wall. The indent markings, located on the forward end of the retainer matched the contour of the high pitch stop weights. These marks measured about 0.567 and 0.847-inches. The marks showed the position of the propeller would be at, or very close to, the feather position.
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Would the bold occur when they moved the prop lever to feather, assuming it was mounted to an airplane and not a test stand?
 
matt152 said:
Reference the subject of this thread. We're talking about a Seneca.
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For the sake of discussion, answer the question. You seem to be the expert on the subject, so I'd like to learn more. I have about 30 hours in piston twins, so I've forgotten most of what I learned 5 years ago.
 
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