OK,
Here we go.....
We flew this afternoon to try and demonstrate the effects of windmilling in fine and coarse and to see if we could stop the prop and see what would happen.
Here is the safety related background - please Ladies and Gents, don't pass comment on how we did it, we briefed for a good 30 minutes regarding how, where what etc. Matt is a competent pilot, I am a check pilot and test schedule pilot on light airplanes, so here goes.
The demonstrations were done in our RV7, IO-360, MT 3 blade hydraulic prop.
We settled on a location overhead a disused 13,000' runway
We started at 7,000'
We cooled the motor prior to the exercise and warmed it for the climb
We had a hard deck set at 4,000' for termination of exercises
We briefed exercises, order and possible anomalies prior to the test
Gosh - got that out of the way, now here is the skinny !!!
Set around 75kts trimmed, around 10" of MP, fine pitch, switched the P-Mags off and the ignition, went to ICO, so no power from the motor. It windmilled and stayed trimmed at the speed and settled at around 1,000fpm descent. Repeated with fully coarse and it settled a bit more at 1,200fpm but then back to 1,000fpm.
At this point, cycling the prop gave a noticeable change. In fine, there was braking, in coarse, it felt as though there was less resistance.
Finally, we tried to stop the prop - Hahahaha
This is Prop 2 video
I tried at stall, hmmmm, I tried with flap, hmmmmm, I tried a bit of a whip stall, hmmmmm.
I could have stopped the prop but only by being brutal and covering the belly with oil - did that last week with exuberant aeros, not again
Conclusions.....
Well, over to you now - you have seen a demonstration, OK, it is a bit relaxed, we aimed to get both fine and coarse demonstrated which we did, we showed the effect of cycling fine to coarse with the motor in ICO.
If I had an engine failure, then yes, I would definitely pull the prop back, it may give me the extra 1/2 mile I need and while windmilling, if I needed more braking low down, it is an option.
A very interesting flight, we both enjoyed it, I think we have interpreted the OP question and feel free to contact off line if you wish to discuss
Mike and Matt
Vid Links
Prop 1
https://youtu.be/OLnEKdKt15M
Prop 2
https://youtu.be/CakLtPkQTIM