Single Engine Constant Speed Propellers

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ssoll7

Filing Flight Plan
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kiwen7
Why are most constant speed equipped single engine aircraft non-feathering?

My initial thought was that the engine might still be operating with a loss of governor oil pressure, so having the blades rotate to fine pitch by default ensures that you wouldn't lose the engine (which might theoretically still have normal oil pressure).

Could anyone speak further to that design philosophy? Given a total loss of engine oil pressure, wouldn't you increase glide range given the ability to feather the prop?
 
ssoll7 said:
Why are most constant speed equipped single engine aircraft non-feathering?

My initial thought was that the engine might still be operating with a loss of governor oil pressure, so having the blades rotate to fine pitch by default ensures that you wouldn't lose the engine (which might theoretically still have normal oil pressure).

Could anyone speak further to that design philosophy? Given a total loss of engine oil pressure, wouldn't you increase glide range given the ability to feather the prop?
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Your intuition is correct. You'd want the failure mode (of the propeller side of the equation) to be to fine pitch in a single engine application, in order to preserve thrust. In a multi engine application that opportunity cost is ameliorated by actual numerical redundancy, with the secondary benefit of significantly reducing drag for OEI ops.

The original Mooney Missile (perhaps the Rocket too?) conversion prescribed a feathering prop. It wasn't a popular retrofit, though I think in present circumstances I'd be more averse to it for the hen's tooth/unobtanioum nature of it when it comes to seeking replacement, than the feathering nature of the prop itself.
 
In the event of a Governor failure you want some pitch to keep the plane in the sky.
 
By my lights, it’s a question of cost, weight, complexity vs. marginal glide benefit. You’re going down, regardless. A little extra distance on a glide probably isn’t worth it.

Unlike in a twin, where you have a chance of staying airborne if you can reduce drag & get the plane cleaned up fast enough.
 
hindsight2020 said:
Your intuition is correct. You'd want the failure mode (of the propeller side of the equation) to be to fine pitch in a single engine application, in order to preserve thrust. In a multi engine application that opportunity cost is ameliorated by actual numerical redundancy, with the secondary benefit of significantly reducing drag for OEI ops.

The original Mooney Missile (perhaps the Rocket too?) conversion prescribed a feathering prop. It wasn't a popular retrofit, though I think in present circumstances I'd be more averse to it for the hen's tooth/unobtanioum nature of it when it comes to seeking replacement, than the feathering nature of the prop itself.
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Exactly right. This allows a single engine airplane to "Fail Operational". Twins fail to feather due to the risk caused by the drag of a non feathered prop. Many high performance aerobatic airplanes also have a fail to feather design like a twin, to avoid an overspeed situation that could cause total failure of the prop and possibly engine mounts.
 
Clip4 said:
The question was why most, does the single engine turbines represent 51% of the single engine airplanes with CS props?
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Because 100% of single engine turbines have CS props. The majority of the single engine piston fleet are Cessna 172s and PA-28s with fixed props.
 
Clip4 said:
The question was why most, does the single engine turbines represent 51% of the single engine airplanes with CS props?
Click to expand...

The point is that there is rationale on both sides so fixation on either side is irrational. There are pros/cons each side and I've had govr failures and engine failures in both set ups.

-Robert
 
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