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Stopped prop in glide

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EMAproducts(at)aol.com
Guest

Posted: Thu Jul 13, 2006 9:31 am Post subject: Stopped prop in glide

In a message dated 7/13/2006 12:10:01 A.M. Pacific Standard Time,  zenith-list(at)matronics.com writes:

  	  Quote: 	
		  I've    always read that a windmilling

prop created more drag than a stopped    one.  Some have even suggested to

try to stop a prop by stalling, to    increase the glide.  That sounds

kinda flakey to me, but to each his    own.

	


 

 IF the stopped prop didn't create less drag why would all the  aircraft companies install a feathering prop on their twin engine  aircraft?  Get with a knowledgeable professional pilot or CFI and have  it explained it to you.  Feathering stops the rotation basically, it also  cuts down on drag but the non rotating is much more important than the actual  feathering of the prop. Many light twins will not maintain altitude with the  prop wind-milling on one engine.

 Elbie Mendenhall

 Pitts Specials to F-27's and most  in-between. 

 DO NOT ARCIVE

randy(at)shadycreekoutlaw
Guest

Posted: Thu Jul 13, 2006 10:31 am Post subject: Stopped prop in glide

It seems to me that a windmilling prop, would cause  more drag.  If the blades stop turning on a helicopter, it won't be  able to autogyro and would fall like a rock...

  

 Randy

 XL Wings - Plans Only

 http://www.n344rb.com

 Do Not Archive

  

 [quote]   ---

ggower_99(at)yahoo.com
Guest

Posted: Thu Jul 13, 2006 11:07 am Post subject: Stopped prop in glide

More easy:

   

  How do the Girocopters fly?    Imagine the "drag" needed to keep them in the air, they only have the power of the pushing (or pulling in Autogiros)  propeller to keep them in the air.

  What will happen IF their "big" propeller will stop in the air,  Sure we can imagine that...

   

  Saludos

  Gary Gower.

  No experience in Giro's,  Just what I have read.

  Do not archive



EMAproducts(at)aol.com wrote:

   	  Quote: 	
		        In a message dated 7/13/2006 12:10:01 A.M. Pacific Standard Time, zenith-list(at)matronics.com writes:

   	  Quote: 	
		  I've always read that a windmilling

prop created more drag than a stopped one.  Some have even suggested to

try to stop a prop by stalling, to increase the glide.  That sounds

kinda flakey to me, but to each his own.

	


  

  IF the stopped prop didn't create less drag why would all the aircraft companies install a feathering prop on their twin engine aircraft?  Get with a knowledgeable professional pilot or CFI and have it explained it to you.  Feathering stops the rotation basically, it also cuts down on drag but the non rotating is much more important than the actual feathering of the prop. Many light twins will not maintain altitude with the prop wind-milling on one engine.

  Elbie Mendenhall

  Pitts Specials to F-27's  and most in-between. 

  DO NOT ARCIVE

mijniljj(at)yahoo.com
Guest

Posted: Thu Jul 13, 2006 4:26 pm Post subject: Stopped prop in glide

When you say that the nonrotating is much more

important than the actual feathering of the prop you

are saying that the airfoil of the prop has more drag

than the flat plate area of the prop and that is

nonsense.

Jim

--- Randy Bryant <randy(at)shadycreekoutlaws.com> wrote:



[quote] It seems to me that a windmilling prop, would cause

 more drag.  If the blades stop turning on a

 helicopter, it won't be able to autogyro and would

 fall like a rock...

 

 Randy

 XL Wings - Plans Only

 http://www.n344rb.com

 Do Not Archive

 

   ---

randy(at)shadycreekoutlaw
Guest

Posted: Thu Jul 13, 2006 7:51 pm Post subject: Stopped prop in glide

I'm saying that a rotating prop must cause more drag than a non-rotating 

prop.  I'm sure that if an engine went out on a helicopter, I'd bet next 

week's paycheck that the pilot had rather still have the rotor turning while 

coming down, that the rotor locked up and not turning...



Randy



Do Not Archive

---

dredmoody(at)cox.net
Guest

Posted: Fri Jul 14, 2006 7:35 am Post subject: Stopped prop in glide

Just the opposite, Jim. A feathered prop is one on which the blades are turned flat to the rotation and inline with the airflow to reduce drag. At least that's what I was taught.



Ed Moody II



Do Not Archive



---- James Ferris <mijniljj(at)yahoo.com> wrote: 

 	  Quote: 	
		   

 

 When you say that the nonrotating is much more

 important than the actual feathering of the prop you

 are saying that the airfoil of the prop has more drag

 than the flat plate area of the prop and that is

 nonsense.

 Jim

dredmoody(at)cox.net
Guest

Posted: Fri Jul 14, 2006 7:51 am Post subject: Stopped prop in glide

As an afterthought, I should have been more clear. 

The biggest reduction in drag occurs as the prop quits rotating. Feathering the prop (turning the blades inline with the airflow) further reduces the drag, but Randy is correct; the additional reduction in drag is not as great as stopping the rotation. Sorry if I clouded the issue with my original response,

Ed Moody II

---- Randy Bryant <randy(at)shadycreekoutlaws.com> wrote: 

 	  Quote: 	
		   I'm saying that a rotating prop must cause more drag than a non-rotating  prop. 

 Randy

 Do Not Archive

 > 

 >

 > When you say that the nonrotating is much more

 > important than the actual feathering of the prop you

 > are saying that the airfoil of the prop has more drag

 > than the flat plate area of the prop and that is

 > nonsense.

fhjamison(at)verizon.net
Guest

Posted: Sat Jul 15, 2006 12:58 pm Post subject: Stopped prop in glide

It is accurate to talk about the larger drag in a  rotating prop since the drag is effectively the size of the rotating prop  disc.

  

 My examiner demonstrated this to me during my  flight exam in 1970, quite effectively.  We were at 3,500 ft when he pulled  the throttle and said okay, your engine has quit, etc.  In the process of  spiraling down he starting talking about this effect and then demonstrated it by  shutting down the engine.  As soon as the prop stopped the drag reduction  was evident.

  

 I have since demonstrated the exact same effect  many times since.  It is a fact, the frontal area of the stopped prop in  less than the drag disc of a windmilling prop, however illogical it may seem to  the casual observer.

  

 Floyd

mijniljj(at)yahoo.com
Guest

Posted: Sat Jul 15, 2006 3:43 pm Post subject: Stopped prop in glide

"the drag is effectively the size of the rotating prop

disc" Give me a break! that is 30 square feet compared

to about 2 to 3 square feet of the stoped prop? Surely

you don't think the drag is ten times as much when the

prop is just turning over the engine as the drag of

the prop  when it is stoped. Maybe two tines as much 

but not ten times as much.

Jim



--- FLOYD JAMISON <fhjamison(at)verizon.net> wrote:



 	  Quote: 	
		   It is accurate to talk about the larger drag in a

 rotating prop since the drag is effectively the size

 of the rotating prop disc.

 

 My examiner demonstrated this to me during my flight

 exam in 1970, quite effectively.  We were at 3,500

 ft when he pulled the throttle and said okay, your

 engine has quit, etc.  In the process of spiraling

 down he starting talking about this effect and then

 demonstrated it by shutting down the engine.  As

 soon as the prop stopped the drag reduction was

 evident.

 

 I have since demonstrated the exact same effect many

 times since.  It is a fact, the frontal area of the

 stopped prop in less than the drag disc of a

 windmilling prop, however illogical it may seem to

 the casual observer.

 

 Floyd


	




__________________________________________________

mijniljj(at)yahoo.com
Guest

Posted: Sat Jul 15, 2006 3:48 pm Post subject: Stopped prop in glide

"the drag is effectively the size of the rotating prop

disc" Give me a break! that is 30 square feet compared

to about 2 to 3 square feet of the stoped prop? Surely

you don't think the drag is ten times as much when the

prop is just turning over the engine as the drag of

the prop  when it is stoped. Maybe two tines as much 

but not ten times as much.

Jim



--- FLOYD JAMISON <fhjamison(at)verizon.net> wrote:



 	  Quote: 	
		   It is accurate to talk about the larger drag in a

 rotating prop since the drag is effectively the size

 of the rotating prop disc.

 

 My examiner demonstrated this to me during my flight

 exam in 1970, quite effectively.  We were at 3,500

 ft when he pulled the throttle and said okay, your

 engine has quit, etc.  In the process of spiraling

 down he starting talking about this effect and then

 demonstrated it by shutting down the engine.  As

 soon as the prop stopped the drag reduction was

 evident.

 

 I have since demonstrated the exact same effect many

 times since.  It is a fact, the frontal area of the

 stopped prop in less than the drag disc of a

 windmilling prop, however illogical it may seem to

 the casual observer.

 

 Floyd


	




__________________________________________________

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Sat Jul 15, 2006 5:29 pm Post subject: Stopped prop in glide

The higher drag of a spinning has a lot more to do with the fact that it 

is moving faster than a stopped prop than it does with the area of the 

prop disk. Drag is a function of speed, among other things.



James Ferris wrote:

 	  Quote: 	
		   

 

 "the drag is effectively the size of the rotating prop

 disc" Give me a break! that is 30 square feet compared

 to about 2 to 3 square feet of the stoped prop? Surely

 you don't think the drag is ten times as much when the

 prop is just turning over the engine as the drag of

 the prop  when it is stoped. Maybe two tines as much 

 but not ten times as much.

 Jim

 

 --- FLOYD JAMISON <fhjamison(at)verizon.net> wrote:

 

> It is accurate to talk about the larger drag in a

> rotating prop since the drag is effectively the size

> of the rotating prop disc.

>

> My examiner demonstrated this to me during my flight

> exam in 1970, quite effectively.  We were at 3,500

> ft when he pulled the throttle and said okay, your

> engine has quit, etc.  In the process of spiraling

> down he starting talking about this effect and then

> demonstrated it by shutting down the engine.  As

> soon as the prop stopped the drag reduction was

> evident.

>

> I have since demonstrated the exact same effect many

> times since.  It is a fact, the frontal area of the

> stopped prop in less than the drag disc of a

> windmilling prop, however illogical it may seem to

> the casual observer.

>

> Floyd

 

 

Bryan Martin
	


do not archive

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

fhjamison(at)verizon.net
Guest

Posted: Mon Jul 17, 2006 7:42 am Post subject: Stopped Prop in Glide

Jim,

  

 Look at George's post that cites from the Naval  Aviator's Handbook.  the Prop disc determines the area of drag but the  ratio / percentage of drag is determined by the angle of the prop blade.   Natuarlly a windmilling prop doesn't present 10 times as much drag, but it does  present a significant drag factor that should be understood and used (or  eliminated) as necessary to effect a safe landing under emergency  conditions.

  

 When you have the opportunity, try it for  yourself.  Its a worthwhile exercise.

  

  

 George, Spot on.  Thanks.

  

  

 R,

 Floyd

  

 Do Not Archive

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