On the RAF Tutor, selecting RPM to ‘LOW’ I.e blue lever fully back, is an initial action in the forced landing drill. The glide performance is significantly better. We practice it during Practice Forced Landings, but the drill is to bring back to low, then keep your hand on the RPM lever until moving it back to full, before taking hand off and opening the throttle. This is to avoid the danger of attempting to go around with the RPM still set low.
I’ve tried this a couple of times during PFLs (obviously with a functioning engine at idle) and the change in glide performance is indeed quite remarkable. What would worry me in a real total engine failure is that I wouldn’t know when the prop would revert to the default ‘fine’ position. I guess that may well come as an unpleasant surprise when you least need it. @Pilot_DAR – and insight into this?
I much thank you for your high quality inputs.
I think I would try to pull back the blue lever, at least it is part of my mental check-list. Actually, when performing a dead-stick landing exercice, with engine at idle and propeller at full RPM, you feel the breaking effect, and high rate of descent.
I clearly lack of some basics knowledge related to mechanical aspects, when thinking about going back to high RPM while the engine is out 
I agree with Jason about side slip, very efficient, all the more I cannot extend the gear :-D
Could someone explain to me why, being at low RPM, the propeller would finally return to fine position / high RPM ? It could actually completely kill your plans if at the wrong moment.
Balliol wrote:
This is to avoid the danger of attempting to go around with the RPM still set low.
In my brain the keyword is “over torque”. Concretely, what would happen if opening the throttle wide open, while the RPM is full back ?
PetitCessnaVoyageur wrote:
Could someone explain to me why, being at low RPM, the propeller would finally return to fine position / high RPM ? It could actually completely kill your plans if at the wrong moment.
Quite. The thing is that in most (all?) SEPs the default prop blade position is in ‘fine’ as that’s where you have max power. This is achieved via the prop governor. More on the topic here: http://www.nashvillecfi.com/commercial/propeller.html and here:http://www.askacfi.com/14393/constant-speed-prop.htm
172driver wrote:
The thing is that in most (all?) SEPs the default prop blade position is in ‘fine’ as that’s where you have max power.
Most, not all. Aerobatic props are a good example: in that case the reasoning is that when you momentarily lose oil pressure doing aerobatics, you don’t want to overspeed the engine. Some props fitted to radial engines apparently also fail coase. Mine is unusual in that it fails in place, which is ‘interesting’ if you happen to be at 40 kts with red line rpm and need to continue the takeoff. I’ve done that a couple of times.
PetitCessnaVoyageur wrote:
Concretely, what would happen if opening the throttle wide open, while the RPM is full back ?
The engine shakes like crazy and makes little power. It may start to detonate (ping). Same as ‘lugging’ your car engine in too high a gear climbing a hill.
Concretely, what would happen if opening the throttle wide open, while the RPM is full back ?
In reality nothing much except you won’t get anywhere near the max power – because the propeller cannot absorb the engine HP at the max rated (governor set) RPM with such a coarse blade pitch. With the prop lever all the way back you get something like 1500 RPM, I think. But I am not about to test it…
Technically you are likely to be operating the engine out of spec. For example on mine you have this:
where the cross-hatched region is not allowed. Speculation has it that it is due to over-stressing the front end of the crankshaft although IMHO if this broke the crank just like that, there would be an awful lot of propellers lying on the ground because probably everybody has visited that region at some stage 
You could exceed MP limits with RPM low and full throttle, and obviously power available would be extremely reduced!
Peter wrote:
With the prop lever all the way back you get something like 1500 RPM, I think. But I am not about to test it…
I did once, with a prop ‘stuck’ in coarse. As I described, it shakes and makes little power. I was able to decrease pitch eventually but until then could not open the throttle too much (due to vibration), or make enough power to climb. Much better when circling a desert landing strip, which is where I was. Otherwise, what you’d want to do in principle is unload the prop (push yoke forward to increase airspeed) and get the engine up to a useful rpm, while opening the throttle.
172driver wrote:
The thing is that in most (all?) SEPs the default prop blade position is in ‘fine’ as that’s where you have max power.
Yes, in most SEPs no oil pressure = full fine…..however the Mooney Rocket and Missile (SEP) conversions for example, have full-feathering props….meaning no oil pressure = feathered….
@Pilot_DAR wrote:
In my Lycoming O-360 powered aircraft, with an MTV-15 prop, the difference between a glide at full fine to a glide at full coarse is about 800 FPM. It glides at 1700 FPM in fine, and 900 FPM in full coarse, all other things being equal. in full coarse pitch, I can shut the engine down completely, and it still windmills, and I can reselect fine as I wish. A normal power off approach for me will be with full coarse pitch selected, and a move back to full fine at landing as convenient. The aerodynamic braking effect is noticeable as I do this. Thus, I can use the propeller for braking.
I am reading again the thread, and better understand your statements.
So, your use of pitch is as I thought initially.
The question, linked with others statements here, is: don’t you fear your propeller to go fine whereas you don’t expect it ?
Besides, how can you still manage pitch whereas the engine is out, i.e. the oil pressure fell off ?
Is it due to the design of your propeller ?
As you suggested, I gonna open my POH, and look for the informations I missed.
