SonexBuilders.net

I was reading this and was wondering if a windmilling prop reverses direction?

"Q: What if I accidentally lean the engine to the point the engine quits while in flight, to bring the engine back to life do I just go full rich?

A: NO! If you lean the engine to the point where it has actually stopped firing, to richen the mixture will probably do nothing as the air speed over the injector spray bar has now become too slow to help even if you go full rich. The best way to bring the engine back to life is to promptly pull the throttle back to idle, if the prop is still wind milling this will immediately restart the engine, then apply full rich and increase power to desired levels. The engine will give plenty of warning that it’s getting towards an over lean state. It will start to run very rough when too lean. Leaning any further will see the engine starve of fuel and stop firing."

No way can you reverse a windmilling prop. You can stop it if you fly slowly enough.

That response seems to be for a fuel injected engine? In a carbureted engine the answer to the question is yes. The windmilling prop is still making a vaccum in the carburetor and firing the plugs, so enrichening the mixture adds fuel back to the mix and it runs.

In other words, a windmilling prop is essentially under the same conditions as when the starter motor is running. It's just the wind turning the crank instead of an electric motor.

My experience with the Aerovee on my Sonex has been that the propeller does not windmill once the engine stops firing. I have tried to restart it by diving fast enough to start it windmilling, but even at > 120mph it won't start turning. That's about as comfortable I felt diving with a stopped propeller. I stopped the engine using the mixture control from idle and restarted it the same as on the ground.

I once accidentally pulled the mixture full lean in flight and the engine quit. I immediately pushed the mixture forward and the engine restarted. The prop had not had time to stop turning.

Just to clarify, the scenario in the original post Q & A is from the Rotec Injector and it's mixture control is completely different than the Aero Carb/Injector…...