Quote:
Originally Posted by flyingchicken
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.
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
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.