[TThurston]

Please excuse me if I'm confused.

But I wonder about the difference between a constant speed prop and fixed pitch prop if my engine dies and I need to glide to a landing. I know some twin props are auto-feathering if the engine dies. What happens on a single with a dead engine (and no oil pressure)? Will the constant speed prop give me more or less drag than a fixed pitch prop?

 

[asav8tor]

To answer your questions,

(1) Goes to flat pitch with no oil pressure

(2) More drag with a C/S at flat pitch vs fixed pitch

HOWEVER,

Your oil pressure does not go to zero with a windmilling prop if you have oil and everything is intact to pump oil.

There has been different opinions tossed around on what happens so here is what I did. Climb up to 5,000 ft and pull the red knob all the way back. Now while gliding with a dead engine I noted "Normal" oil pressure. I could move the prop control back and a very significant drag reduction. Push it forward very significant increase in drag. You could very well use this to control your energy state in a forced landing situation. Just remember it works backwards..... FWD to slow down, AFT to speed up. I tried it at different IAS; the effect is more pronounced at 130 vs 90.

 

[RVjim]

Prop for best glide with a dead engine

A fixed pitch CRUISE propeller or a counterweighted blade CS propeller. (With the loss of oil pressure, the CS counterweighted blades go to high pitch.)

I have routinely flown my RV-3 with both a fixed pitch cruise propeller and a CS propeller out of Camarillo Airport. (Camarillo Airport has a 3,000' displaced threshold. Pattern altitude is 800? AGL.)

With the CS propeller set at 2600 RPM downwind abeam the displaced threshold using full flaps at pattern altitude, I would pull the throttle to idle and immediately turn onto the base leg (nose way down). I would land in the first 500 feet of the runway.

With the fixed pitch propeller abeam the displaced threshold using full flaps at pattern altitude, I would pull the throttle to idle and fly the length of the displaced threshold and back to get to the same landing point on the runway. At least 5,000? farther than with the standard CS propeller.

I routinely fly my RV-6A out of Oxnard Airport. (Oxnard Airport has a 1,000? displaced threshold. Pattern altitude is 1,000? AGL)

With the standard CS propeller set at 2600 RPM downwind abeam the displaced threshold using full flaps at pattern altitude, I had to add power to have enough airspeed too flare for the landing. Without adding power, I think I can make the runway if I only use 20 degrees of flaps.

Regards,
Jim Ayers