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Kolb quit revealed
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russk50(at)gmail.com
Guest

Posted: Sat Mar 31, 2012 6:51 am Post subject: Kolb quit revealed

In re the famous/infamous "Kolb Quit", as RV 40072 says, it's nothing but a stall. However, the Kolb has a straight wing, which means it will stall all at once; it's flying one minute, and then at 2-3 MPH slower, the whole wing has stalled. That's why it's been called violent, gets your attention and can be terrifying. That's also why you should never get too near a stall unless you're just a few feet above the ground.

Those who have flown GA aircraft are used to a much more gentle stall -- that's because the wing has some twist, or wash-out, where the wing root stalls first and the rest of the wing is still developing lift. The tips stall last, so the ailerons are still effective as long as possible.

To be accurate, stalls are a function of angle of attack, not airspeed; but since we don't have AOA indicators we have to use airspeed instead. It does work. 

An experienced pilot will do it mostly by feel anyway, at the landing flare.

Russ K

On Mar 30, 2012, at 11:13 PM, Rv40072wrote:



 	  Quote: 	
		   

 

 I have been following these discussions about Kolb quits for some time.    In case anyone has not figured it out, Kolb quit is nothing more than a stall.  The first thing to grasp is that stalls are not a function of airspeed. They are function of Angle of Attack.  Depending on weight, g-load applied, air density, the airplane will stall at different airspeeds., and can in fact be stalled at any airspeed.  The airplane will however, always stall at the same angle of attack. The following link will give one a good start on understanding stalls. http://en.wikipedia.org/wiki/Stall_(flight)

 

 Vic, cudos for pursuing a better understanding, but instead of focusing on what airspeed it stalls at, focus on how it feels just before it stalls.  The second alternative would be to build a simple angle of attack indicator, then you would have a visual warning of impending stall.  

 

 Have fun, and safe flying.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=369668#369668

racerjerry

Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY

Posted: Sat Mar 31, 2012 6:54 am Post subject: Re: Kolb quit revealed

Well, I am certainly glad that we got rid of the hostility and returned to a friendly technical discussion.  



Vic claims that he is experiencing a difference in stall speed at different ATTITUDES.  On the surface this seems implausible, but he may be quite correct.  Pitot tube error at higher angles of attack could be causing a false (lower) airspeed indication.  I would suggest repositioning the pitot to a slightly lower angle to confirm.

_________________
Jerry King

Last edited by racerjerry on Sat Mar 31, 2012 7:25 am; edited 2 times in total

Vic Peters

Joined: 30 Oct 2009
Posts: 54
Location: Millinocket, Maine

Posted: Sat Mar 31, 2012 8:18 am Post subject: Kolb quit revealed

Hey guys and others

    No more hostility from me. I'm brewing  my own beer. 

 I agree with everyone so far.

 These recent posts are very helpful. I like the  idea of 2 finger stick control and I've read up on stalls and 

 ground effect on wicked pedia till my head  exploded.

  

   " The critical angle of attack in steady straight and level  flight can be attained only at low airspeed"

 " Ground effect causes higher air pressure under the wing (more lift) and  lower drag"

  

 So it still just doesn't make sense that at  altitude straight and level no stall at 35mph (unless I'm sinking and don't know  it).   Ground effect should lower stall speed not be the same. Pitot  could be wrong but always seems to match gps, no wind ofcourse. VG's are'nt  really working in level flight but at high angle of attack they really kick  in. (28mph)

 That's what they are supposed to do I think. The  boys at Kolb got that stall in an Extra by lowering the leading  edge

 of the wing. I assume to get lift from the big  flat fuselage bottom.

  

 Still stumped

   [quote][b]

_________________
Vic
912ul Xtra
Maine
Too old to cut the mustard but not the cheese.

pj.ladd(at)btinternet.com
Guest

Posted: Sat Mar 31, 2012 9:42 am Post subject: Kolb quit revealed

<<That's also why you should never get too near a stall unless you're just a 

few feet above the ground.>>



Good grief!.  If ever a statement is guaranteed to get someone killed that 

is it.

A  stall  `a few feet ` above the ground will just allow enough room for a 

nosedive straight onto mother Earth.



The idea of making a  landing is to stall a few INCHES above the ground.



Cheers



Pat

pj.ladd(at)btinternet.com
Guest

Posted: Sat Mar 31, 2012 9:45 am Post subject: Kolb quit revealed

Russ?



(Stalling a few feet above the ground.)



I just realised who sent that message. I cannot believe it was you. Tell me 

you didn`t mean it



Pat

lcottrell

Joined: 29 May 2006
Posts: 1494
Location: Jordan Valley, Or

Posted: Sat Mar 31, 2012 10:20 am Post subject: Kolb quit revealed

Maybe your nose is shorter than ours. You do remember that we seem to be just a little different over here.

Larry



On Sat, Mar 31, 2012 at 11:41 AM, Pat Ladd <pj.ladd(at)btinternet.com (pj.ladd(at)btinternet.com)> wrote:

  	  Quote: 	
		  --> Kolb-List message posted by: "Pat Ladd" <pj.ladd(at)btinternet.com (pj.ladd(at)btinternet.com)>

  

 <<That's also why you should never get too near a stall unless you're just a few feet above the ground.>>

 

 Good grief!.  If ever a statement is guaranteed to get someone killed that is it.

 A  stall  `a few feet ` above the ground will just allow enough room for a nosedive straight onto mother Earth.

 

 The idea of making a  landing is to stall a few INCHES above the ground.

 

 Cheers

 

 Pat

 

 

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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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-- 

If you forward this email, or any part of it, please remove my email address before sending.

 



  [quote][b]

_________________
do not archive

Eugene Zimmerman

Joined: 10 Jan 2006
Posts: 392

Posted: Sat Mar 31, 2012 10:57 am Post subject: Kolb quit revealed

Kinne,



Not sure what airplane you are describing but it certainly is not a characteristic any of Homer's designs I am familiar with.



If you are terrified by the stall characteristic of the Kolb planes I'd strongly suggest you either never park your butt in another airplane, or have an experienced pilot take you up to altitude in most any plane other than a kolb, and do an intentional stall to recalibrate your meter for "terrified".

Gene Z



On Mar 31, 2012, at 10:50 AM, kinne russ wrote:

 	  Quote: 	
		  In re the famous/infamous "Kolb Quit", as RV 40072 says, it's nothing but a stall. However, the Kolb has a straight wing, which means it will stall all at once; it's flying one minute, and then at 2-3 MPH slower, the whole wing has stalled. That's why it's been called violent, gets your attention and can be terrifying. 	






 [quote][b]

zeprep251(at)aol.com
Guest

Posted: Sat Mar 31, 2012 12:20 pm Post subject: Kolb quit revealed

If you have had the opportunity to fly a Kolb model with vg's and the same Kolb model without vg's, all the way through it's speed range including a full stall,you will have formed a very definite opinion about their worth on this designed wing.

G.AmanMK3C



 



 



 



--

byoungplumbing(at)gmail.c
Guest

Posted: Sat Mar 31, 2012 4:18 pm Post subject: Kolb quit revealed

ok folks,,,,,   I had time this afternoon  to do some research,,,,   I found this on the Kolb web sight,  frequently asked questions page. http://www.kolbaircraft.com/faqs.htm       I should have done the search before I posted the last question.

  

 I don't know how this was determined...  maybe  if Dennis Souder is around maybe he could comment.

  

 anyway if the statement by Kolb is correct the  entire wing wont stall at once.

  

 boyd young

 mkii

 utah

  

  

  

 quote 

 "It does not look like there is any twist in your  wings, are you sure that is okay?

  

 You are correct. Our wings are completely flat on  the bottom. Twist is used to ensure that the root of the wing will stall before  the wing tip. If the wing tip were to stall first, the airplane would be very  dangerous to fly. Our wings are low aspect ratio which means  they do not have a very long span for their cord; low aspect ratio wings have  very good stall characteristics, the root will stall before the wing tips  do. In addition, the rectangular plan form that we use is less prone to  tip stalling than a tapered wing. So, for our design wings, twist is totally  unnecessary, plus it makes building the wings much easier."  end  quote

  

  

   [quote][b]

John Hauck

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

Posted: Sat Mar 31, 2012 6:55 pm Post subject: Kolb quit revealed

Not sure what airplane you are describing but it certainly is not a

characteristic any of Homer's designs I am familiar with.



Gene Z

 



Gene Z/Folks:



Don't think Russ K has near as much time in a Kolb as Gene Z does.



To me, a Kolb, all models, stall just the opposite of a Cessna 152, etc.

Lots of Kolb pilots get in trouble because of this gentle stall

characteristic.  They get themselves into a mush/stall, the aircraft remains

in a level attitude, and the pilot does not realize he is stalling.  That's

a pretty gentle stall in my book.



In ground effect, the Kolb stalls and drops, just like it does at altitude.

Only difference is the Kolb smacks the ground in ground effect.



Stalling a Kolb from a couple feet in ground effect will not put the nose in

the ground and will probably not kill you, at least in the US.  Maybe in GB.





john h

mkIII

Titus, Alabama

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

John Hauck

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

Posted: Sat Mar 31, 2012 7:01 pm Post subject: Kolb quit revealed

If you have had the opportunity to fly a Kolb model with vg's and the same

Kolb model without vg's, all the way through its speed range including a

full stall, you will have formed a very definite opinion about their worth

on this designed wing.

G.AmanMK3C

 

I have been fortunate to have done that.  The difference with and without

VG's was negligible. 



There was an improvement in softening a full stall three point landing if I

initiated one a little high.



john h

mkIII

Titus, Alabama

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

John Hauck

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

Posted: Sat Mar 31, 2012 7:47 pm Post subject: Kolb quit revealed

I would suggest repositioning the pitot to a slightly lower angle to

confirm.



--------

Jerry King

 



Mr. Steve Whitman shared with me at Sun and Fun 1993, to cut my pitot tube

at a 45 degree angle to improve ASI accuracy at high angles of attack.  This

came out during a discussion of how to improve accuracy of static pressure.

I asked him, initially, what type static system he used in his aircraft.  He

told me he used nothing.  His static port was the static port on the rear of

the ASI.  Told me the stall speed was going to indicate the same whether

accurate or not.    



john h

mkIII

Titus, Alabama

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

pj.ladd(at)btinternet.com
Guest

Posted: Sun Apr 01, 2012 4:52 am Post subject: Kolb quit revealed

Maybe in GB.



John,

the gravity is MUCH stronger over here.Bent undercarriage at least.And of 

course it depends on the pilots reaction. In your case with thousands of 

hours the reaction is keep the stick back and give a burst of power. Thats 

it. A tyro will probably do what he has been taught to do when the airspeed 

falls Push the stick forward. He dives smartly into the ground.



The trouble with this entire question is that there are so many variables.

Firstly. I reckon that no two Kolbs whether kit or factory built are EXACTLY 

the same. Even in the unlikely event of everything during the building being 

done precisely  the same with every angle exactly similar no two planes have 

the same colour scheme so there is at once a variation in weight and 

balance.

The pilots are all different. They arrange their cockpits differently.Some 

have minimal instrumentation. Some look like 747`s.

Normally this makes no difference but we are trying to carry out an EXACT 

test or comparison.

So the base line for all other measurements is flawed.



Secondly. The sort of test we are trying to do is being carried out in 

`real` conditions. Variable wind, variable approach angle, variable speeds, 

(as no ones ASI is the same)



The sort of testing which we are doing under field conditions can only 

properly be carried out in a wind tunnel. We just cannot expect to produce 

results with spittin` distance of each other



The `Kolb quit` means nothing really. It is just a nice alliterative phrase 

to describe something we have all experienced. Its a stall. At 500ft you 

ease the stick forward and it goes away. Do that at 5ft and it catches you 

out. Thats Kolb Quit`



I hope no one produces an answer that irrevocably solves all this. What 

should we talk about?



Cheers



Pat

beauford

Joined: 25 Apr 2007
Posts: 127
Location: Brandon, FL

Posted: Sun Apr 01, 2012 5:16 am Post subject: Kolb quit revealed

--

racerjerry

Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY

Posted: Sun Apr 01, 2012 6:36 am Post subject: Re: Kolb quit revealed

â€œMr. Steve Whitman shared with me at Sun and Fun 1993, to cut my pitot tube at a 45 degree angle to improve ASI accuracy at high angles of attack...â€



john h



Now THAT is interesting, and makes sense too.  A straight cut pitot tube would present less ram area to incoming air at any angle other than straight ahead; circle turns into an ellipse with increased vertical dimension at higher angles of attack.  With an angle cut pitot tube, the same area is presented in level flight; but at higher angles of attack, increased area is presented to incoming air (angle cut with longest portion of tube at top).  



John, thank you for sharing.

_________________
Jerry King

Last edited by racerjerry on Fri Apr 20, 2012 4:30 am; edited 1 time in total

zeprep251(at)aol.com
Guest

Posted: Sun Apr 01, 2012 6:53 am Post subject: Kolb quit revealed

Well John,

 We agree on Most things.

 G.Aman

    

  

     

  

     

  

    --

pj.ladd(at)btinternet.com
Guest

Posted: Sun Apr 01, 2012 9:15 am Post subject: Kolb quit revealed

..Seafoam...?

Seafoam?. What is that? I have never heard of it. Please tell me all about 

it.

racerjerry

Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY

Posted: Mon Apr 02, 2012 6:23 am Post subject: Re: Kolb quit revealed

â€¦Seafoam? That is something you get when you pee into the surf.

_________________
Jerry King

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