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Cross wind capability of the Mk IIIC
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John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Tue Sep 22, 2009 2:44 pm Post subject: Cross wind capability of the Mk IIIC

> Have you ever tried Dead stick gliding and landings in your MK III ??? 

My minimum descent rate in my Kolb MK III Xtra is 500 FPM at 55 MPH and 1800 

RPM - Minimum Idle power for my Rotax 912-S.   When I shut down the engine 

and stop the prop completely, my descent rate increases to 900 Feet per 

minute, it is much worse  [Evil or Very Mad]    This was the total opposite 

of what I was expecting, but I have done this a number of times and this is 

just the way it is in my Kolb.   It does not make any sense and goes against 

theory, but I have tried varying the airspeeds, and tested this quite a 

number of times with always the same result, when I stop the prop instead of 

idle at 1800 RPM, my glide is reduced by a huge amount.

 	  Quote: 	
		  

 Mike


	




Mike B/Gang:



Yes, I have done many dead stick landings in my mkIII.



I don't remember the numbers, but I do remember the glide being much better 

with a dead stick.



Minimum rpm at closed throttle on my 912ULS while flying is about 2200 rpm. 

On the ground I have my idle set for about 1700 rpm.



Sometimes Kolbs do some screwy things that "experts" with other airplanes 

can not explain.  This increased rate of decent while dead stick may be one 

of them.  When I get home and start flying again I'll check it out and see 

what I come up with.



john h

mkIII

Rock House, Oregon

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Tue Sep 22, 2009 2:46 pm Post subject: Cross wind capability of the Mk IIIC

 	  Quote: 	
		   Does the prop windmill on a 912 engine? It won't on a 503 with no clutch.


	


Possum/Gang:



Not from dead stick, but my 912ULS does increase from around 1600-1700 rpm 

to about 2200 rpm during gliding decents.



 	  Quote: 	
		  From dead stick, the prop stays stuck.  


	


john h

mkIII

Rock House, Oregon

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Tue Sep 22, 2009 4:38 pm Post subject: Re: Cross wind capability of the Mk IIIC

Rick,



If the prop at cruise power is producing positive thrust and the prop stopped is producing negative thrust (drag), then at some point between cruise rpm and zero rpm the net thrust goes from positive to negative. At that rpm for that airspeed, the net thrust is exactly zero. With the rpm above that (being driving by a running engine), there is some positive net thrust. With the engine running at any rpm below that transition point from positive to negative the net result is drag all the way down to and including zero rpm. 



Maybe John H's MkIII has better glide with the engine and prop stopped than at idle power at the same airspeed but none of my airplanes have done that nor does Mike Bigelow's MkIIIX, according to his recent report. During my next flight I will note the descent speeds at my normal approach airspeed with engine at idle and with the engine stopped. I'll be mightily surprised if the descent rate with the prop stopped is lower than when at idle power. But I'm open to being surprised. Nothing like empirical evidence to prove one right or wrong.



In either case, I agree with John H. that it is a good idea to get familiar with your airplanes' glide characteristics with the engine actullay stopped. This is not something you want to learn when it is an actual emergency.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Tue Sep 22, 2009 5:13 pm Post subject: Cross wind capability of the Mk IIIC

Not that I would ever advocate not practicing anything a pilot thinks is useful in an emergency, but a far more useful skill IMHO is being able to instantly recognize what Langewiesche called "the point that does not move". If you can recognize that it won't matter what condition the airplane is in or the airspeed you're flying you'll make the field if it's possible at all. 



Rick Girard

do not archive



On Tue, Sep 22, 2009 at 7:38 PM, Thom Riddle <riddletr(at)gmail.com (riddletr(at)gmail.com)> wrote:

 [quote]--> Kolb-List message posted by: "Thom Riddle" <riddletr(at)gmail.com (riddletr(at)gmail.com)>

  

 Rick,

 

 If the prop at cruise power is producing positive thrust and the prop stopped is producing negative thrust (drag), then at some point between cruise rpm and zero rpm the net thrust goes from positive to negative. At that rpm for that airspeed, the net thrust is exactly zero. With the rpm above that (being driving by a running engine), there is some positive net thrust. With the engine running at any rpm below that transition point from positive to negative the net result is drag all the way down to and including zero rpm.

  

 Maybe John H's MkIII has better glide with the engine and prop stopped than at idle power at the same airspeed but none of my airplanes have done that nor does Mike Bigelow's MkIIIX, according to his recent report. During my next flight I will note the descent speeds at my normal approach airspeed with engine at idle and with the engine stopped. I'll be mightily surprised if the descent rate with the prop stopped is lower than when at idle power. But I'm open to being surprised. Nothing like empirical evidence to prove one right or wrong.

  

 In either case, I agree with John H. that it is a good idea to get familiar with your airplanes' glide characteristics with the engine actullay stopped. This is not something you want to learn when it is an actual emergency.

  

 --------

 Thom Riddle

 Buffalo, NY

 Kolb Slingshot SS-021

 Jabiru 2200A #1574

 Tennessee Prop 64x34

 

 A complex system that works is invariably found to have evolved from a simple system that works.

   - John Gaule

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=264415#264415

 

 

 

 

 

 

 

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 [b]

_________________
The smallest miracle right in front of you is enough to make you happy....

Possums

Joined: 03 Nov 2007
Posts: 247

Posted: Tue Sep 22, 2009 6:58 pm Post subject: Cross wind capability of the Mk IIIC

At 03:11 PM 9/22/2009, you wrote:

  	  Quote: 	
		  --> Kolb-List message posted by: "Thom Riddle" <riddletr(at)gmail.com>



 [size=12]Rick,



 To help clear up my understanding of your working theory please answer the following questions:



 1- When flying at cruise power or higher, is your prop producing a net positive thrust force or net drag force (negative thrust)?



 2- Would the glide performance of your airplane with power off and prop stopped be better or worse than if the prop were not even on the engine? In other words, would the total drag of the airplane gliding at a given speed be more or less with a stopped prop or no prop at all on the airplane?



 Thanks for your help.



 --------

 Thom Riddle 	


 I don't under stand how a stopped prop (you can consider the frontal area of the prop to be the total source of drag) would slow

 you down more than a spinning prop. Either It's pushing the plane forward producing thrust at whatever speed or at 

 the other extreme, the whole swept area of the spinning prop is considered as a flat drag plate when it's windmilling. 

 Or you have the magic touch and can spin the prop at the exact RPM to create no drag at all. 

 It would bet better with no prop at all or a folding prop as seen on some self

 propelled gliders. The cleaner you plane is the more this might matter. 

 I don't think it would make much difference in a Quicksilver.

  

 

     [quote][b]

_________________
Possum

Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Tue Sep 22, 2009 7:54 pm Post subject: Re: Cross wind capability of the Mk IIIC

[quote="Possums"]At 03:11 PM 9/22/2009, you wrote:

  	  Quote: 	
		  --> Kolb-List message posted by: "Thom Riddle" <riddletr>



 [size=12]Rick,



 To help clear up my understanding of your working theory please answer the following questions:



 1- When flying at cruise power or higher, is your prop producing a net positive thrust force or net drag force (negative thrust)?



 2- Would the glide performance of your airplane with power off and prop stopped be better or worse than if the prop were not even on the engine? In other words, would the total drag of the airplane gliding at a given speed be more or less with a stopped prop or no prop at all on the airplane?



 Thanks for your help.



 --------

 Thom Riddle 	


 I don't under stand how a stopped prop (you can consider the frontal area of the prop to be the total source of drag) would slow

 you down more than a spinning prop. Either It's pushing the plane forward producing thrust at whatever speed or at 

 the other extreme, the whole swept area of the spinning prop is considered as a flat drag plate when it's windmilling. 

 Or you have the magic touch and can spin the prop at the exact RPM to create no drag at all. 

 It would bet better with no prop at all or a folding prop as seen on some self

 propelled gliders. The cleaner you plane is the more this might matter. 

 I don't think it would make much difference in a Quicksilver.

  

 

      	  Quote: 	
		  [b] 	




******************************************************



According to this web site, there is a negative thrust from a windmilling prop at some combination of windmilling rpm and glide speed.

http://home.scarlet.be/comicstrip/Drag%20prop/Drag%20From%20Prop.htm



Don't know if it's true or not, but interesting.



Richard Pike

MKIII N420P (420ldPoops)

pj.ladd(at)btinternet.com
Guest

Posted: Wed Sep 23, 2009 1:11 am Post subject: Cross wind capability of the Mk IIIC

I don't under stand how a stopped prop (you can consider the frontal area of 

the prop to be the total source of drag) would slow

 you down more than a spinning prop.>



If you practice emergency landings by closing the throttle to idle you are 

in for a rude awakening when the engine really stops. You will not make the 

field you expect.



been there etc.



Cheers



Pat

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Wed Sep 23, 2009 2:52 am Post subject: Re: Cross wind capability of the Mk IIIC

...If you practice emergency landings by closing the throttle to idle you are 

in for a rude awakening when the engine really stops. You will not make the field you expect....



Pat,



Thank you. That is exactly the point I've been trying to make. That a stopped prop creates more drag than a prop at idle power. 



This has nothing at all to do with a WINDMILLING prop. A windmilling prop is one that is being driven by the relative wind in glide with the engine inop. NOTHING LIKE an engine at idle power.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Wed Sep 23, 2009 3:35 am Post subject: Cross wind capability of the Mk IIIC

Richard,



  http://home.scarlet.be/comicstrip/Drag%20prop/Drag%20From%20Prop.htm

  



[url=http://home.scarlet.be/comicstrip/Drag%20prop/Drag%20From%20Prop.htm][/url]Excellent link. Thanks for posting. 

  



I think part of the confusion or perhaps misunderstanding is with the term windmilling. When the engine is running, the prop is not windmilling, it is being powered by the engine. In speed reduced props(gear or belt) like most Kolbs have, there is no windmilling with a dead engine at normal approach glide speeds. I doubt that my direct drive Jabiru engine will windmill either at my normal approach speed with engine stopped but don't know because I have not yet tried it, but will during my next flight. My contention is that a stopped prop produces more drag than a prop when the engine is at idle power. I've said nothing about a windmilling prop which indeed produces more drag than a stopped prop as this link demostrates. 

  



When the engine is running the prop is not windmilling. The idle power prop/engine speed is greater in gliding flight than on the ground because the AOA of the blade is less as the forward speed increases as your link shows very well. The reduced AOA is responsible for the higher rpm at idle power vs sitting on the ground at zero forward speed. This reduced AOA of blade at increased forward speed also explains why WOT static rpm is less than WOT during climb. The forward speed reduces the AOA of the blade and thus the drag of the blade allowing higher RPM.

  



Thom in Buffalo

  [quote][b]

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

russkinne(at)mac.com
Guest

Posted: Wed Sep 23, 2009 5:26 am Post subject: Cross wind capability of the Mk IIIC

I wholly second Rick G's comments. Every pilot should read and heed Langewiesche's STICK AND RUDDER. It could keep him alive some  day.From the little I read of the recent crash in  CT, the pilot may have been  making major adjustments while on final -- flaps on  & off, throttle, stick. Much better to get STABILIZED on final, then make whatever minor adjustments you have to. 

While aiming at  'the point that doesn't move'  at your intended touchdown point.

FWIW

Russ K

do not archive



On Sep 22, 2009, at 9:10 PM, Richard Girard wrote:

 	  Quote: 	
		  Not that I would ever advocate not practicing anything a pilot thinks is useful in an emergency, but a far more useful skill IMHO is being able to instantly recognize what Langewiesche called "the point that does not move". If you can recognize that it won't matter what condition the airplane is in or the airspeed you're flying you'll make the field if it's possible at all. 



Rick Girard

do not archive



On Tue, Sep 22, 2009 at 7:38 PM, Thom Riddle <riddletr(at)gmail.com (riddletr(at)gmail.com)> wrote:

  	  Quote: 	
		  --> Kolb-List message posted by: "Thom Riddle" <riddletr(at)gmail.com (riddletr(at)gmail.com)>

 

 Rick,

 

 If the prop at cruise power is producing positive thrust and the prop stopped is producing negative thrust (drag), then at some point between cruise rpm and zero rpm the net thrust goes from positive to negative. At that rpm for that airspeed, the net thrust is exactly zero. With the rpm above that (being driving by a running engine), there is some positive net thrust. With the engine running at any rpm below that transition point from positive to negative the net result is drag all the way down to and including zero rpm.

 

 Maybe John H's MkIII has better glide with the engine and prop stopped than at idle power at the same airspeed but none of my airplanes have done that nor does Mike Bigelow's MkIIIX, according to his recent report. During my next flight I will note the descent speeds at my normal approach airspeed with engine at idle and with the engine stopped. I'll be mightily surprised if the descent rate with the prop stopped is lower than when at idle power. But I'm open to being surprised. Nothing like empirical evidence to prove one right or wrong.

 

 In either case, I agree with John H. that it is a good idea to get familiar with your airplanes' glide characteristics with the engine actullay stopped. This is not something you want to learn when it is an actual emergency.

 

 --------

 Thom Riddle

 Buffalo, NY

 Kolb Slingshot SS-021

 Jabiru 2200A #1574

 Tennessee Prop 64x34

 

 A complex system that works is invariably found to have evolved from a simple system that works.

  - John Gaule

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=264415#264415

 

 

 

 

 

 

 

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 arget="_blank">http://www.matronics.com/Navigator?Kolb-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

 ===========

 

 

 

 



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