Extended Glide...

[pierre smith]

Gary. my -10 will glide 400 FPM better with the prop control pulled all the way back...900 FPM vs 500 FPM. It really is amazing how much drag is reduced.

Best,

 

[smokyray]

It depends...

Gary,

During glide testing with my HR2 I experimented with both fine and full coarse pitch settings for glide. The glide numbers differ greatly between the two, the coarse pitch being nearly identical to my FP numbers on the RVX. However comma, they could be misleading as when most CS props lose oil pressure during engine failure, the hub springs push them to fine pitch. Therefore figure worst case with a CS prop post engine failure unless the WW can go to coarse pitch with no oil pressure.

V/R
Smokey
www.fly-4-life.com

 

[NickAir]

Oil pressure

Gary,

During glide testing with my HR2 I experimented with both fine and full coarse pitch settings for glide. The glide numbers differ greatly between the two, the coarse pitch being nearly identical to my FP numbers on the RVX. However comma, they could be misleading as when most CS props lose oil pressure during engine failure, the hub springs push them to fine pitch. Therefore figure worst case with a CS prop post engine failure unless the WW can go to coarse pitch with no oil pressure.

V/R
Smokey
www.fly-4-life.com

Is this true with the Hartzel C/S?

 

[Bill Dicus]

extended glide

IIRC the Hartzell goes to fine pitch and MT CS prop to coarse pitch. If there is no oil pressure the engine might be seized and drag of a stopped prop is much less. I have no figures for RV's.

 

[Kevin Horton]

IIRC the Hartzell goes to fine pitch and MT CS prop to coarse pitch. If there is no oil pressure the engine might be seized and drag of a stopped prop is much less. I have no figures for RV's.

Actually, it depends on whether you have an aerobatic prop or not. A non-aerobatic prop will go to fine pitch if oil pressure is lost. An aerobatic prop has counterweights and springs that help it go to coarse pitch if oil pressure is lost.

Both Hartzell and MT make both types of props, so you cannot generalize behaviour by manufacturer.

 

[gereed75]

I have played with my WW 200 RV with the red knob pulled. It will change pitch with just a windmilling prop. Not sure if it goes full coarse, but it does change, and glide improves.

I assumed that there was enough oil pressure during windmilling to get it to change pitch. I will do some checking to see a few things:

1) How much oil pressure is being produced as a dead (undamaged) engine windmills.

2) What is the RPM difference between full fine and full coarse when windmilling.

3) What is the difference in descent rate between the two for my 6.

I've always known it is better at full coarse, but I practice and compute at full fine, figuring with a dead engine with a jug blown off or some other problem you might not be able to effect prop pitch (as Smokey suggests). Maybe you get more lucky and it seizes and stops the prop with the best glide of all, but I practice at fine pitch - worst case.

I'll let you all know if I get a chance to get some real numbers. If I see numbers as good as Pierre, that would be a sweet ace in the hole!!

PS - Just to confirm FYI, the standard WW is on a McCauley hub, is not counterweighted and does go to fine pitch with no oil pressure.

 

[Finley Atherton]

Gary,

During glide testing with my HR2 I experimented with both fine and full coarse pitch settings for glide. The glide numbers differ greatly between the two, the coarse pitch being nearly identical to my FP numbers on the RVX. However comma, they could be misleading as when most CS props lose oil pressure during engine failure, the hub springs push them to fine pitch. Therefore figure worst case with a CS prop post engine failure unless the WW can go to coarse pitch with no oil pressure.

V/R
Smokey
www.fly-4-life.com

My Hartzell will stay coarse (although I don't know if it is full coarse) with a windmilling dead engine. These are figures I collected some time ago.

At 70 kts with the mixture at idle cut-off and prop control full in:
Oil pressure 55 psi
RPM 1350

At 70 kts with the mixture at idle cut-off and the prop control fully out (coarse):
Oil pressure 50 psi
RPM 900.

My windmilling dead engine glide performance is much better with the prop set coarse rather than fine.

Fin 9A
0-320, 9:1 compression ratio