FP Prop that has stopped in-flight

[Bill Dicus]

We have tried this deliberately (over the airport) and been successful at restart and also inadvertently when the engine quit and stopped rotating in a flat spin. In a Pitts S-1S with FP metal prop had to dive to about 180 mph ias to start rotation. IIRC the Cessna 150 only took about 135. Our Pitts S-2A with CS Hartzell took almost 190 ias (200 hp Lyc). As they say, YMMV!

[bkthomps]

i think instead of inertia you guys mean momentum, no?

then again, i've been drinking

[Snowflake]

Originally Posted by bkthomps

i think instead of inertia you guys mean momentum, no?

Well, we're throwing the term inertia around kind of loosely... The concept of getting something moving again from a standstill is what I was getting at. Until the flywheel effect of the heavier prop takes over (which I doubt would kick in until it is turning), the forces working to get it started are the same... Just the air forces on the blades, balanced against the compression of the cylinder that it's stopped against. To get it to *start* turning is independent of the construction material.

The problem is that there are so many factors affecting each in-air restart that it is probably not realistic to conclude that wood props are easier to get started... Unless someone has two same diameter, same pitch, same shape propellors, one wood and one metal, and wants to do some tests.

[NickAir]

My -6 had a 0-320 w/Senenich metal prop. It would windmill down to 75 easy.

[Neal@F14]

Originally Posted by Kyle Boatright

The difference between an air restart of wood vs metal props is pretty substantial.

This has been my experience too. The metal Sensenich prop did an air-restart much more effortlessly, and at much lower airspeed than either of the Aymar-Demuth or Sterba wood props I've personally observed. O-320's on all three aircraft.

[Bad Sheila]

I suppose the consensus is that you keep the prop windmilling until all efforts of a re-start have failed. (Assuming you have altitude to play with) You then make the decision whether to stop the prop or not with the realization that you will lose some glide distance by slowing down enough to stop the prop? Comments?

[Bad Sheila]

I suppose the consensus is that you keep the prop windmilling until all efforts of a re-start have failed. (Assuming you have altitude to play with) You then make the decision whether to stop the prop or not with the realization that you will lose some glide distance by slowing down enough to stop the prop? Comments?

[mfshook62]

Another consideration that needs to be factored in to this discussion is density altitude.

[Snowflake]

Originally Posted by Neal@F14

This has been my experience too. The metal Sensenich prop did an air-restart much more effortlessly, and at much lower airspeed than either of the Aymar-Demuth or Sterba wood props I've personally observed. O-320's on all three aircraft.

What diameter and pitch were the wood and metal props? All identical?

Originally Posted by Bad Sheila

I suppose the consensus is that you keep the prop windmilling until all efforts of a re-start have failed. (Assuming you have altitude to play with) You then make the decision whether to stop the prop or not with the realization that you will lose some glide distance by slowing down enough to stop the prop? Comments?

At university we ran some simulation calculations to see what made the most sense in the case of an engine failure. I looked but I can't find my course notes right now... There is a loss of glide distance due to the exercise of stopping the prop, but above a certain altitude you can gain that loss back with the longer glide distance with a stopped prop. For a 100HP Cessna 150, I seem to recall that break point was in the low 1000's of feet, like 2000-3000'.

[Jerry Cochran]

I probably missed something, but what's wrong with just using the starter?

But, just like Brian. I've been drinking...