No question about that! My posts were just rebutting a common misconception about the reason why. That misconception being that high drag comes from the engine/gearbox, it doesn't it comes from the propeller, and it's very significant while wind milling in fine pitch.

In a light twin I've noticed 500fpm difference between closed throttle fine pitch and feathered. Remember that a prop needs to be unstalled with sufficient tip speed in order create massive drag, which is the situation on a typical engine out. If you can't feather then try to get it stopped if you need the glide.

Total agreement, everything including the improvement gained by stopping the engine IF feathering fails AND the prop wind milling in FINE. Caveat though is that stopping the engine with prop wind milling in FINE may not be safe and practical, even with power reduction on the remaining engine the respective VMC and Vs for the configuration may make this unwise.

Your assertion agrees with the data from the graph I posted and the engineering papers I so far found on the topic.

If the propeller was fitted with a sprag clutch, such that the propeller could windmill freely your assertion would still be correct, because it is the propeller that causes the drag, not the gearbox/engine.

Dangerous, foolish, and incorrect assertions on the part of the new guy.

I strongly recommend that any students reading disregard; his counsel could just get you killed.

Captain Beaker,
Can you provide some real world examples where your predictions would apply?
Because while the underlying physics might be sound, its rather academic, as it dosen't take into account the real world system interactions that makes your situation a transient state at best.

Makes a huge difference on a CE-208. You have to feather that thing, the glide distance chart requires it.

The graph shows 3 things:

1. Engine/Gearbox is not the cause of the drag, e.g. compare the scenario at say 30 degree pitch.

2. Flat pitch and wind milling creates very significant drag, the drag coefficient increases massively as the blade moves towards 0 degrees. This is entirely consistent with the need to feather in an aircraft cable of fine pitch. It is also consistent with safety devices needed to ensure blade angle remains outside the 'beta range' while in flight.

3. It's consistent with my own observations and the flight manual, for an aircraft fitted with a fixed pitch prop of approx 18degrees found in a C-172. i.e. wind-milling or stationary does not seem to have a very noticeable effect. It's consistent with the need to set low rpm on a constant speed single.

All of this is entirely consistent with every flight manual I have come across.

The original poster asked an interesting academic question, so maybe I provide some thoughtful input on that academic discussion. I haven't proposed anything contradictory to what you expect to find in the flight manual.

Couple of thoughts, just for fun :D

How come the propeller creates so much drag in the positive beta range, even when driven by the substantial torque of a turbine in flight idle?

While a helicopter is in auto-rotation, the blades free wheel because it is fitted with a sprag clutch. If we consider the blades to be a large windmilling prop rotated 90 degrees wouldn't the resistance from the engine be advantageous? ;)

Probably best I get my coat.:)

(Sigh).

Coarse vs. Course.

Sprague vs. Sprag.

A little knowledge is a dangerous thing.



http://i3.kym-cdn.com/photos/images/...40/656/f26.jpg

True, but you'd need to be very near stall to get a fixed-pitch prop to stop on a typical light ASEL. If the motor is damaged that might make it easier to stop.

Once stopped, you may be able to pitch for best glide without the prop spinning again, thereby enjoying reduced drag and increased glide range.

Would I try it? Maybe under some hypothetical situation where I was going to be gliding for a long time and needed every bit of range. You're going to waste some energy slowing the plane so you'd need a lot of altitude to get an ROI. Would I recommend it? No.

This is just another thing to be aware of. If I have altitude and need the performance/ glide, I'm stopping the prop. If there's a good place to land under me then Ill enjoy the extra drag. A Senneca crashed just short of its destination because the dead engine was turning.