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  #121  
Old 03-10-2009, 07:38 PM
L.Adamson's Avatar
L.Adamson L.Adamson is offline
 
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Quote:
Originally Posted by Kevin Taylor View Post
If your that concerned with drag I'm surprised you have a nosewheel!
Nosewheels are practical. If I wanted to be macho, I'd ride a Harley to the local bar...

L.Adamson

edit...........P/S, I'd go taildragger for an RV8 too. They look better, that way. It could sure use a C/S though. It's the weight and balance thing. Save more for a C/S!

Last edited by L.Adamson : 03-10-2009 at 07:40 PM.
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  #122  
Old 03-10-2009, 09:47 PM
Captain Avgas Captain Avgas is offline
 
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Location: Melbourne, Australia
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Default Maybe...but maybe not.

Quote:
Originally Posted by Steve Brown View Post
It is easier to slow with a CS prop, but the glide range is longer with a FP prop..... if the motor quits I'll have about 30% longer glide range.
I have heard that said before but I suspect it may not be true. I would not be surprised if in fact you could glide further with a CS prop.

If the engine quits and the prop stops spinning I doubt there would be any meaningful difference in the glide range between a CS and FP prop. Both should have very good glide range with the prop stopped.

If on the other hand (and this is the more common scenario) the prop keeps spinning (driven by the air) then there will always be sufficient oil pressure generated by the engine to drive the prop governor. In other words the pilot can pull the prop controller right out and the prop will go to full coarse. That will feel like you just released the brakes. At full coarse the CS prop may in fact have a coarser pitch than a FP cruise prop. If it does it should present less drag and therefore the aircraft should glide further (all other things being equal).
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RV7A
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  #123  
Old 03-10-2009, 10:12 PM
gasman gasman is offline
 
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Quote:
Originally Posted by Captain Avgas View Post
I have heard that said before but I suspect it may not be true. I would not be surprised if in fact you could glide further with a CS prop.

If on the other hand (and this is the more common scenario) the prop keeps spinning (driven by the air) then there will always be sufficient oil pressure generated by the engine to drive the prop governor. In other words the pilot can pull the prop controller right out and the prop will go to full coarse. That will feel like you just released the brakes. At full coarse the CS prop may in fact have a coarser pitch than a FP cruise prop. If it does it should present less drag and therefore the aircraft should glide further (all other things being equal).
So then, your on final during an emergency landing and you have the prop at full coarse with oil pressure from the engine windmilling, you have the airspeed pegged plus a little for good luck, and just then the spinning motor is slow enough that the oil pressure drops off and the prop goes flat. You just lost that 10 knots that kept you in the air. How do you deal with this?
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  #124  
Old 03-11-2009, 05:54 AM
Captain Avgas Captain Avgas is offline
 
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Quote:
Originally Posted by gasman View Post
So then, your on final during an emergency landing and you have the prop at full coarse with oil pressure from the engine windmilling, you have the airspeed pegged plus a little for good luck, and just then the spinning motor is slow enough that the oil pressure drops off and the prop goes flat. You just lost that 10 knots that kept you in the air. How do you deal with this?
From my experience I think you'll find that the windmilling prop will maintain enough engine oil pressure to make the prop governor effective right down to the stall. Slower than that obviously doesn't matter.

My advice to you (and other pilots) would be to test this out in your particular aircraft BEFORE you need to do an engine-out emergency landing.

Personally I have added the "Prop full coarse" as the last item on my engine out check list (in the event that the prop is still windmilling).

Believe me when I say that the difference in glide range between an engine out glide with a CS prop at cruise pitch compared with full coarse is REALLY dramatic. Kill your engine one day by leaning out to idle cut-off (at altitude) and try it out....it feels like you just jettisoned a drag parachute

There may be specific advantages to a FP prop (less cost, less maintenance, less weight) but the extra glide range argument is most likely a myth...if you understand that the prop controller is still functional if the prop is still windmilling. But the truth is that many pilots of CS aircraft don't realise that fact.
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  #125  
Old 03-11-2009, 06:06 AM
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pierre smith pierre smith is offline
 
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Default Only if you need it...

Quote:
Originally Posted by Captain Avgas View Post

.........Believe me when I say that the difference in glide range between an engine out glide with a CS prop at cruise pitch compared with full coarse is REALLY dramatic. .
....since there may be a suitable field right under you

Regards,
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  #126  
Old 03-11-2009, 07:14 PM
Captain Avgas Captain Avgas is offline
 
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Quote:
Originally Posted by pierre smith View Post
....since there may be a suitable field right under you

Regards,
Hi there Pierre. It's good to hear again from the man that did the 250' engine-out turnback after take-off in his RV6A (and posted the video on Youtube) thus effectively killing off the great VansAirforce Turnback thread (stopped all the naysayers in their tracks !!!!)

Of course as you and I both know once we have actually reached that "suitable field" we can always throw the prop to full fine if the fan is still windmilling to cut speed as required. Going suddenly from full coarse to full fine should just about put you through the windshield.
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Last edited by Captain Avgas : 03-12-2009 at 03:58 AM.
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  #127  
Old 03-11-2009, 09:16 PM
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Ron Lee Ron Lee is offline
 
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I have a FP prop. If magically I could change it to a CS prop at no cost I would do it now. When you fly with other RVs and you have to have them throttle back so you can maintain their climb rate you will understand.

Always fly by yourself and in most cases the FP is just fine...but never as good as a CS prop. Fact.
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  #128  
Old 03-14-2009, 07:35 PM
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N941WR N941WR is offline
 
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Default Hey Larry

Did you see this thread?

Funny, but I have never seen that happen with a FP prop.

Sorry, I just had to say that!
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  #129  
Old 03-14-2009, 07:45 PM
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grjtucson grjtucson is offline
 
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Quote:
Originally Posted by N941WR View Post
Funny, but I have never seen that happen with a FP prop.
Oh come on! It turns out is was just a bad zerk. That could happen to anyone, even on a fixed pitch prop...
.
.
.
er, well not that.

But it's a small price (plus some money) to pay to actually be able to:
- climb
- slow down
- fly aerobatics
- have a plane that is in CG
- have a cool blue knob
- dozens of other things that fixed pitch planes can't

George

TOTALLY in jest
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Tucson, AZ - RV-7 Standard Build
Empennage Completed 1/06, Wings Completed 11/06, Fuselage Done 9/08, Panel Wiring Done 7/19. About to haul it to the airport.
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  #130  
Old 03-14-2009, 07:53 PM
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L.Adamson L.Adamson is offline
 
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Quote:
Originally Posted by N941WR View Post
Did you see this thread?
Of course. I see most of the threads! At least changing a zerk fitting will be easier than removing the spinner, loosening six bolts, to change the prop pitch each time....

L.Adamson
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