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Stoped / windmilling propeller drag

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propellerdesign(at)tele2.
Guest

Posted: Tue May 29, 2007 12:01 pm Post subject: Stoped / windmilling propeller drag

Hi Guys,

  

 I have a question from a Polish Pilot, if drag is  less or not from a free spinning propeller (engine with clutch) or stopped  propeller, when engine is stopped or out, and how much it will do on sink  rate?

  

 I think we all agree on the fact that drag is  higher if propeller is rotating and driving the engine, then if propeller and  engine is stopped.

  

 I can't think about a better place to ask this  question then here on this active list with all different engine / prop  setup that exists on kitfoxes.

  

 The Polish guy is replacing his VW with a modern  BMW with a 2,75/1 reduction on a Tulak airplane.

  

 Best 

  

 Jan Carlsson 

   [quote][b]

wingsdown(at)verizon.net
Guest

Posted: Tue May 29, 2007 1:27 pm Post subject: Stoped / windmilling propeller drag

For  those that would argue differently. If the prop did not create drag in free  rotation helicopters could not auto rotate.  As far as how much. It take  some nerve  to test that feature. I never intentionally shut off the  engine in flight. There must be some formula to do the math. I did once go beta  and full power. That was way different being pulled forward while in the air.  Went back to regular flight real quick. Fun though.  

  

 Rick

 [quote]   

   --

crazyivan

Joined: 25 Aug 2006
Posts: 62
Location: Pensacola

Posted: Tue May 29, 2007 2:23 pm Post subject: Re: Stoped / windmilling propeller drag

There are a few guys on this list that like to shut the engine off in flight.



I, on the other hand, am too chicken.  What I can offer is the drag difference between different pitches of prop.  I had my IvoProp set for a flat (climb) pitch and it was tough to get the prop to spin at 2000rpm at idle on final at 55mph but the drag was noticable.  When I had a fatter pitch set for cruise, I had to be careful to keep the rpm above 1800 (gear box chatter) and I had a harder time slowing down...I had to make a flatter approach.  



There wasn't a big difference, but it was noticable.  If I lost the engine on final, I'm certain that there would be reduced drag from a stationary prop.  I'm not sure how much and I ain't gonna find out on purpose unless I'm over the great salt flats.

_________________
Dave
Piper PA-22/20

rjdaugh

Joined: 30 Aug 2006
Posts: 195

Posted: Tue May 29, 2007 2:42 pm Post subject: Stoped / windmilling propeller drag

Rick,  

Shut off the engine.    

   

Perhaps it helps that I started out as a glider pilot, but I enjoy shutting off the engine and enjoying quiet flight.  Sometimes I do it just to show passengers that it is no big deal.  Sometimes, like this past Sunday, I do it to work the thermals.   The Kitfox does not have a great glide ratio, but that is not what is needed to work thermals.  What is needed is a low sink rate – lower than the vertical speed of the thermal.  I get about a 500 fpm sink rate at about 63 mph airspeed.   That’s not too bad for a starter glider, but a high performance glider can get under 200 fpm.  

   

If your engine is off for a long time, start it early enough so you can warm the engine before you get close to the ground.  Usually, unless you are going to do a dead stick landing this will be only 6 – 12 minutes anyway so your engine is still warm.    

   

To get back on topic, with my old prop, I had to slow nearly to full stall to get the engine to stop windmilling.  So it was easy to measure sink rate with it windmilling or without.  I didn’t test it real carefully, but sink rate was over 600 fpm with the prop windmilling versus 500 with the prop stopped.  

   

With my new prop, I can get the prop to stop windmilling if I just slow to about 55 mph.  I haven’t tried to measure windmilling versus stopped.  

   

To start the engine, I just have to bump the starter and it starts right off with the air pushing it.  

   

Try it.  You will like it!  And it will make you a more confident pilot.  

   

Randy  

     

Randy Daughenbaugh,  N10NH  

Black Hills of South Dakota, - Near Mount Rushmore  

Home Strip, Grass   Room in Hangar for visitors  

Series 5/7 (7 Firewall Forward) 912S, Warp Drive Taper Tip  

Gross Weight 1320 lbs, Flying since November 2004  

  

         

  

From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Rick

 Sent: Tuesday, May 29, 2007 3:26 PM

 To: kitfox-list(at)matronics.com

 Subject: RE: Stoped / windmilling propeller drag  

  

     

For those that would argue differently. If the prop did not create drag in free rotation helicopters could not auto rotate.  As far as how much. It take some nerve  to test that feature. I never intentionally shut off the engine in flight. There must be some formula to do the math. I did once go beta and full power. That was way different being pulled forward while in the air. Went back to regular flight real quick. Fun though.    

    

   

    

Rick  

  [quote]  

--

_________________
Randy
Kitfox 5/7 912S
Black Hills, South Dakota

kirkhull(at)kc.rr.com
Guest

Posted: Tue May 29, 2007 3:30 pm Post subject: Stoped / windmilling propeller drag

From the aerodynamics classes that I took ( what I remember of them anyway) a freewheeling prop looks like a solid circle to the air. In other words a lot of drag.  As far as stopping the engine in flight , it was removed from the training curriculum for a reason.  

         

  

From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Rick

 Sent: Tuesday, May 29, 2007 4:26 PM

 To: kitfox-list(at)matronics.com

 Subject: RE: Stoped / windmilling propeller drag  

  

     

For those that would argue differently. If the prop did not create drag in free rotation helicopters could not auto rotate.  As far as how much. It take some nerve  to test that feature. I never intentionally shut off the engine in flight. There must be some formula to do the math. I did once go beta and full power. That was way different being pulled forward while in the air. Went back to regular flight real quick. Fun though.    

    

   

    

Rick  

  [quote]  

--

lcfitt(at)sbcglobal.net
Guest

Posted: Tue May 29, 2007 4:08 pm Post subject: Stoped / windmilling propeller drag

I have never done it but this topic came up during the trip to So. Cal. and 

the other three pilots had done it and our most experienced pilot said he 

guessed it would be 20-30° greater glide.  That corresponds pretty well with 

Randy's experience.



Lowell Fitt

Cameron Park, CA

Model IV-1200 R-912 UL Warp

1998 850 hrs.

---

N81JG(at)aol.com
Guest

Posted: Tue May 29, 2007 4:15 pm Post subject: Stoped / windmilling propeller drag

A wind-milling, undriven rotor (no motor drag) is what allows a  helicopter to descend in autorotation. A stopped rotor will not allow an  autorotation, only descent like a brick. Hence rotating blades have more  drag.

  

 John Greaves

 VariEze N81JG



See what's free at AOL.com. 

  [quote][b]

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Tue May 29, 2007 6:29 pm Post subject: Re: Stoped / windmilling propeller drag

[quote="N81JG(at)aol.com"]A wind-milling, undriven rotor (no motor drag) is what allows a  helicopter to descend in autorotation. A stopped rotor will not allow an  autorotation, only descent like a brick. Hence rotating blades have more  drag.

  

 John Greaves

 VariEze N81JG

Close... In a helicopter, autorotation is possible from the stored energy in the blades.  If you can go to negative pitch, you can acutally gain rotor RPM.  To auto rotate, you go negative on the pitch and fly with the cyclic as you normaly would.  you start you flare a little later than normal and pretty much arrest forward speed then you pull the pitch to gently set her down...all this happens very fast.  A huey can store enough energy to autorotate, land then lift off do a complete pedal turn and set back down... if it was empty to begin with..



This is an issue I am wrestling with on my Avid with the clutch.. If I have an engine out, I still fall like a rock with the prop windmilling and cant stop it.

 

See what's free at AOL.com. 

   	  Quote: 	
		  [b]

_________________
DO NOT ARCHIVE
Leonard Perry aka SNAKE
Soldotna AK
Avid "C" / Mk IV
582 (147 hrs and counting on the rebuild)
IVO IFA
Full Lotus 1450
#1 snake oil salesman since 1-22-2009

I would rather die trying to live, than to live trying not to die....

msm_9949(at)yahoo.com
Guest

Posted: Wed May 30, 2007 11:43 am Post subject: Stoped / windmilling propeller drag

Leonard,

   

  Have you actually tried it in your clutch-equipped Avid? I.e, turn off power and let the prop freewheel? If so, please advise as to sink rate and other performance characteristics you experienced. I'd like to know what to expect before I try it myself.

  



akflyer <akflyer_2000(at)yahoo.com> wrote:

   	  Quote: 	
		  

This is an issue I am wrestling with on my Avid with the clutch.. If I have an engine out, I still fall like a rock with the prop windmilling and cant stop it.



--------

Leonard Perry

Soldotna AK

Avid "C" / Mk IV 

582 IVO IFA

Full Lotus 1260

95% complete

	




Marco Menezes

Model 2 582 N99KX

        Shape Yahoo! in your own image.   [url=http://us.rd.yahoo.com/evt=48517/*http://surveylink.yahoo.com/gmrs/yahoo_panel_invite.asp?a=7]Join our Network Research Panel today![/url]  [quote][b]

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Thu May 31, 2007 6:19 am Post subject: Re: Stoped / windmilling propeller drag

I have not flown the Avid yet as I am still one wing short... But, I have flown my Brothers KF II with the clutch set up.  You dont have to kill the engine to get it to free wheel just pull the power back to an idle.  With the power at idle and the prop free wheeling, at 55-60 I am dropping around 1000' min.  I would hope this would go up if the prop stopped turning. 



 I have tested it on a cub with the prop windmilling and with the prop stopped.  When starting from 6000' and crossing cook inlet, it was a matter of making the far shore and having to slip to hit the beach with the prop stopped, and having to re-start or swim about a mile to mile and a half in real cold water to get to the beach if I let it wind mill.. Until I had tried it I would never have figured it would make that much difference.



I put the clutch on my avid as most of the time I will be dealing with cold weather (rough starts and warm up) and float flying (nice to warm up without moving).



I hope to have mine in the air by the end of the month and will do some testing with fine and coarse pitch and see how much of a difference that makes.

msm_9949(at)yahoo.com
Guest

Posted: Thu May 31, 2007 6:48 am Post subject: Stoped / windmilling propeller drag

I've also cut power to idle at altitude in my clutch-equipped model II. In this configuration, I can usually hold the descent rate to about 600 fpm, at 50-55 mph indicated. I suspect that with the engine completely off, it will sink much faster.



akflyer <akflyer_2000(at)yahoo.com> wrote:  [quote]--> Kitfox-List message posted by: "akflyer" 



I have not flown the Avid yet as I am still one wing short... But, I have flown my Brothers KF II with the clutch set up. You dont have to kill the engine to get it to free wheel just pull the power back to an idle. With the power at idle and the prop free wheeling, at 55-60 I am dropping around 1000' min. I would hope this would go up if the prop stopped turning. 



I have tested it on a cub with the prop windmilling and with the prop stopped. When starting from 6000' and  crossing cook inlet, it was a matter of making the far shore and having to slip to hit the beach with the prop stopped, and having to re-start or swim about a mile to mile and a half in real cold water to get to the beach if I let it wind mill.. Until I had tried it I would never have figured it would make that much difference.



I put the clutch on my avid as most of the time I will be dealing with cold weather (rough starts and warm up) and float flying (nice to warm up without moving).



I hope to have mine in the air by the end of the month and will do some testing with fine and coarse pitch and see how much of a difference that makes.



--------

Leonard Perry

Soldotna AK

Avid "C" / Mk IV 

582 IVO IFA

Full Lotus 1260

95% complete





Read this topic online       Sick sense of humor? Visit Yahoo! TV's  [url=http://us.rd.yahoo.com/evt=47093/*http://tv.yahoo.com/collections/222]Comedy with an Edge [/url]to see what's on, when.     [quote][b]

kerrjohna(at)comcast.net
Guest

Posted: Thu May 31, 2007 9:20 am Post subject: Stoped / windmilling propeller drag

the conclusion below might not prove out in practice.  with the reduced drag of a stationary propeller the 50-55 mph indicated will be attainable at a lesser decent angle.

  

 John Kerr

  

 [quote]-------------- Original message -------------- 

From: Marco Menezes <msm_9949(at)yahoo.com> 

I've also cut power to idle at altitude in my clutch-equipped model II. In this configuration, I can usually hold the descent rate to about 600 fpm, at 50-55 mph indicated. I suspect that with the engine completely off, it will sink much faster.



akflyer <akflyer_2000(at)yahoo.com> wrote:   	  Quote: 	
		  --> Kitfox-List message posted by: "akflyer" 



I have not flown the Avid yet as I am still one wing short... But, I have flown my Brothers KF II with the clutch set up. You dont have to kill the engine to get it to free wheel just pull the power back to an idle. With the power at idle and the prop free wheeling, at 55-60 I am dropping around 1000' min. I would hope this would go up if the prop stopped turning. 



I have tested it on a cub with the prop windmilling and with the prop stopped. When starting from 6000' and crossing cook inlet, it was a matter of making the far shore and having to slip to hit the beach with the prop stopped, and having to re-start or swim about a mile to mile and a half in real cold water to get to the beach if I let it wind mill.. Until I had tried it I would never have figured it would make that much differen  ce.

I put the clutch on my avid as most of the time I will be dealing with cold weather (rough starts and warm up) and float flying (nice to warm up without moving).



I hope to have mine in the air by the end of the month and will do some testing with fine and coarse pitch and see how much of a difference that makes.



--------

Leonard Perry

Soldotna AK

Avid "C" / Mk IV 

582 IVO IFA

Full Lotus 1260

95% complete





Read this topic online   Sick sense of humor? Visit Yahoo! TV's [url=http://us.rd.yahoo.com/evt=47093/*http://tv.yahoo.com/collections/222]Comedy with an Edge [/url]to see what's on, when.  	  Quote: 	
		  

	
	
[b]

clint_bazzill(at)hotmail.
Guest

Posted: Thu May 31, 2007 12:41 pm Post subject: Stoped / windmilling propeller drag

That much sink at that airspeed.  Like a Cessna with full flaps.  Clint

From: Marco Menezes <msm_9949(at)yahoo.com>

Reply-To: kitfox-list(at)matronics.com

To: kitfox-list(at)matronics.com

Subject: Re: Re: Stoped / windmilling propeller drag

Date: Thu, 31 May 2007 07:45:35 -0700 (PDT)

I've also cut power to idle at altitude in my clutch-equipped model II. In 

this configuration, I can usually hold the descent rate to about 600 fpm, at 

50-55 mph indicated. I suspect that with the engine completely off, it will 

sink much faster.

akflyer <akflyer_2000(at)yahoo.com> wrote:  

"akflyer"

I have not flown the Avid yet as I am still one wing short... But, I have 

flown my Brothers KF II with the clutch set up. You dont have to kill the 

engine to get it to free wheel just pull the power back to an idle. With the 

power at idle and the prop free wheeling, at 55-60 I am dropping around 

1000' min. I would hope this would go up if the prop stopped turning.

I have tested it on a cub with the prop windmilling and with the prop 

stopped. When starting from 6000' and crossing cook inlet, it was a matter 

of making the far shore and having to slip to hit the beach with the prop 

stopped, and having to re-start or swim about a mile to mile and a half in 

real cold water to get to the beach if I let it wind mill.. Until I had 

tried it I would never have figured it would make that much difference.

I put the clutch on my avid as most of the time I will be dealing with cold 

weather (rough starts and warm up) and float flying (nice to warm up without 

moving).

I hope to have mine in the air by the end of the month and will do some 

testing with fine and coarse pitch and see how much of a difference that 

makes.

--------

Leonard Perry

Soldotna AK

Avid "C" / Mk IV

582 IVO IFA

Full Lotus 1260

95% complete

Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=115755#115755

Marco Menezes

Model 2 582 N99KX

---------------------------------

Sick sense of humor? Visit Yahoo! TV's Comedy with an Edge to see what's on, 

when.

_________________________________________________________________

PC Magazine’s 2007 editors’ choice for best Web mail—award-winning Windows 

Live Hotmail.

msm_9949(at)yahoo.com
Guest

Posted: Thu May 31, 2007 3:13 pm Post subject: Stoped / windmilling propeller drag

Pretty draggy. Alot like full flaps on a 172. In fact, I've also used the big fan to steepen glide on short final.



Clint Bazzill <clint_bazzill(at)hotmail.com> wrote:  [quote]--> Kitfox-List message posted by: "Clint Bazzill" 



That much sink at that airspeed. Like a Cessna with full flaps. Clint

From: Marco Menezes 

Reply-To: kitfox-list(at)matronics.com

To: kitfox-list(at)matronics.com

Subject: Re: Re: Stoped / windmilling propeller drag

Date: Thu, 31 May 2007 07:45:35 -0700 (PDT)



I've also cut power to idle at altitude in my clutch-equipped model II. In 

this configuration, I can usually hold the descent rate to about 600 fpm, at 

50-55 mph indicated. I suspect that with the engine completely off, it will 

sink much faster.



akflyer  wrote: --> Kitfox-List message posted by: 

"akflyer"



I have not flown the Avid yet as I am still one wing short... But, I have 

flown my Brothers KF II with the clutch set up. You dont have to kill the 

engine to get it to free wheel just pull the power back to an idle. With the 

power at idle and the prop free wheeling, at 55-60 I am dropping around 

1000' min. I would hope this would go up if the prop stopped turning.



I have tested it on a cub with the prop windmilling and with the prop 

stopped. When starting from 6000' and crossing cook inlet, it was a matter 

of making the far shore and having to slip to hit the beach with the prop 

stopped, and having to re-start or swim about a mile to mile and a half in 

real cold water to get to the beach if I let it wind mill.. Until I had 

tried it I would never have figured it would make that much difference.



I put the clutch on my avid as most of the  time I will be dealing with cold 

weather (rough starts and warm up) and float flying (nice to warm up without 

moving).



I hope to have mine in the air by the end of the month and will do some 

testing with fine and coarse pitch and see how much of a difference that 

makes.



--------

Leonard Perry

Soldotna AK

Avid "C" / Mk IV

582 IVO IFA

Full Lotus 1260

95% complete





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=115755#115755







Marco Menezes

Model 2 582 N99KX



---------------------------------

Sick sense of humor? Visit Yahoo! TV's Comedy with an Edge to see what's on, 

when.



_________________________________________________________________

PC Magazine’s 2007 editors’ choice for best Web mail—award-winning Windows 

Live Hotmail.       [url=http://us.rd.yahoo.com/evt=48250/*http://searchmarketing.yahoo.com/arp/sponsoredsearch_v9.php?o=US2226&cmp=Yahoo&ctv=AprNI&s=Y&s2=EM&b=50]Pinpoint customers [/url]who are looking for what you sell.    [quote][b]

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