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The Kolb drop
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apilot(at)surewest.net
Guest

Posted: Wed Feb 20, 2008 9:04 am Post subject: The Kolb drop

VG's definitely make my Mark III land easier and lighter.  I lost around 3 or 4 mph cruise with them.  Hopefully, I will find an airspeed that makes good use of the VG effect and increase my range by lowering the rpms required to give a slower and more economical cruise.  I would like 60 mph at a fuel burn of 2 gallons per hour.  Probably the VG effect will not happen until the airspeed lowers to around 50 mph.  Need a wind tunnel.

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Wed Feb 20, 2008 9:21 am Post subject: Re: The Kolb drop

Seems many are missing the point in this thread, the reasons for the Kolb Drop are well known, and with proper landing techniques, it can be dealt with.



The more important point is that VG"s make the Kolb Drop much less severe.  Pilots are human, no one lands perfectly all the time.   VG's can make the difference between bent gear, and just a less than perfect landing.  I would much rather have plane that is more forgiving on landing, rather than one that probably result in damage the first time I flare a bit high.  



It is obvious that the people that are saying VG's don't make landings in a Kolb much more docile are the people that dont have VG's.



Mike Bigelow

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

gaman(at)att.net
Guest

Posted: Wed Feb 20, 2008 9:23 am Post subject: The Kolb Drop

Maybe a little refresher course on gravity and airspeed would be helpful if they are having difficulty with the earth jump concept.Someone said the earth sucks when you get that close to it.



---

Possums

Joined: 03 Nov 2007
Posts: 247

Posted: Wed Feb 20, 2008 3:48 pm Post subject: The Kolb Drop

At 10:24 AM 2/20/2008, you wrote:

 	  Quote: 	
		  



May be Kolb Drop should be redefined as Earth Jump.  Earth Jump can be

equally applied to all aircraft with out giving undue credit and it easily

explains away why the earth is not in the correct position when these pilots

flared or were repositioning their aircraft.



Jack B. Hart FF004

Winchester, IN



do not archive


	


Basic Flying Rules:

1. Try to stay in the middle of the air.

2. Do not go near the edges of it.

3. The edges of the air can be recognized by the appearance of the ground,

     buildings, sea, trees and interstellar space.

     It is much more difficult to fly there.

_________________
Possum

johnjoyes

Joined: 06 Nov 2007
Posts: 3
Location: Reading, UK

Posted: Thu Feb 21, 2008 1:40 am Post subject: Re: The Kolb drop

Those of you arguing about the "Kolb Drop" might like ti hear my completely different experience, when I too bent the legs of my Mk3.

I was storming in, two-up, much faster than usual, a steep descent, almost a dive, with no flap, throttle fully off. When I came to flare, the stick came all the way back to the stop with zero resistance, while the plane carried straight on (into the ground) with no attempt to flare.

My inspector says I would be amazed to know how many aircraft there are out there with some combination of attitide and speed where the tail is caught in a vortex from the main wing, and does nothing. 

Because of the speed, this could not be a stall. The remedy is to learn the characteristics of your plane, at a safe altitude. Now I always keep a bit of power on for landing, to ensure airflow over the tail. 

I like the idea of VG's and hope to try them out. But in view of my experience, the place to put them first is on the underside of the tailplane just ahead of the elevator.

JJ

pj.ladd(at)btinternet.com
Guest

Posted: Thu Feb 21, 2008 2:50 am Post subject: The Kolb drop

arguing about the "Kolb Drop" >>



If we are to continue talking unendingly about this phenomenon, even when 

there cannot be a single syllable which has not been repeated ad infinitum, 

can we please call it the `Kolb Quit` not the  `Kolb Drop`.



Kolb Quit has a nice alliterative feel to it and makes it easier for those 

of us who move their lips when they read.



Cheers



Pat

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Thu Feb 21, 2008 4:29 am Post subject: The Kolb drop

At 04:41 AM 2/21/2008, johnjoyes wrote:



 	  Quote: 	
		  Because of the speed, this could not be a stall.


	


Not saying it's what happened, but stall is a function of AOA, not speed.



 	  Quote: 	
		  I like the idea of VG's and hope to try them out. But in view of my 

experience, the place to put them first is on the underside of the 

tailplane just ahead of the elevator.


	


If the tailplane had stalled, that might have helped.   But VG's on the 

tail won't keep the wing from stalling.



-Dana

--

  Why is it called tourist season if we can't shoot at them?

John Hauck

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

Posted: Thu Feb 21, 2008 5:44 am Post subject: The Kolb drop

> If we are to continue talking unendingly about this phenomenon, even when

 	  Quote: 	
		   there cannot be a single syllable which has not been repeated ad 

 infinitum, can we please call it the `Kolb Quit` not the  `Kolb Drop`.

 >
	


 	  Quote: 	
		   Cheers



 Pat


	




Patrick:



Sorry to correct you but, Kolb aircraft do not suffer from Kolb Quit or Kolb 

Drop, only the pilots do.



Personally, I do not like the terms.  They tend to implie Kolb aircraft have 

a problem, when in reality there is none.  Pilots of some Kolbs have a 

problem landing.  In fact, some Kolb pilots have problems taxiing and flying 

them.



Take care,



john h

mkIII

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

pj.ladd(at)btinternet.com
Guest

Posted: Thu Feb 21, 2008 7:21 am Post subject: The Kolb drop

Sorry to correct you but, Kolb aircraft do not suffer from Kolb Quit or Kolb

Drop, only the pilots do>>



Absolutely right John, as usual.. If an aircraft loses flying speed 6 ft up 

instead of 6 inches it will stop flying however it is spelt



Cheers



Pat.

ceengland(at)bellsouth.ne
Guest

Posted: Thu Feb 21, 2008 5:09 pm Post subject: The Kolb drop

Charlie England wrote:

 	  Quote: 	
		   There's a much better option. Just install a message 'filter' so you 

 never see posts from people you find offensive. It works great; only 

 fails when someone else responds to the offensive poster (hint, hint). 

 If you need help setting up the filter, I'm sure there are several 

 people on this list who would help, including me.



 Charlie



 N27SB(at)aol.com wrote:

> Only an idiot would not recognize there very real fact.   I have 

> instructed in the Kolb, and as a CFI in general aviation aircraft. 

>  

>  

> That's it, I've had it, time to unplug for a while.

>  

> Steve

>  

> In a message dated 2/19/2008 8:37:52 A.M. Eastern Standard Time, 

> orcabonita(at)hotmail.com writes:

>

>     

>

>     Kolb's have the characteristic of suddenly dropping hard on

>     landing if very good technique is not used.  Cessna and other

>     most other training aircraft are not like this, they are much

>     more forgiving on landing and tolerant of the pilot being a

>     little off speed, or a little high in the flare.  Only an idiot

>     would not recognize there very real fact.   I have instructed in

>     the Kolb, and as a CFI in general aviation aircraft.  In General

>     aviation aircraft, I can let students get much further off speed,

>     or flare a lot higher on landing than in a Kolb, and not bend the

>     gear or result in a very hard landing.   Hundreds of students

>     flare high, land slow, etc etc every day in Cessnas and other

>     aircraft and you do not constantly bend the gear, partly due to

>     stronger gear, and partly to do much more forgiving aerodynamics.

>

>     The other fact is that on my Kolb MK III, VG's have done a lot to

>     correct this bad habit of dropping suddenly and hard upon

>     landing.  VG's do not solve this problem entirely, but my Kolb MK

>     III is not anywhere near as critical in landing as it was, and it

>     does not drop nearly as hard if I am a few feet high as it did

>     without VG's.  I don't care so much about the theory, or what

>     some may say about stalls, the FACT is that VG's make landings

>     much easier and less critical in my Kolb, and that is a great thing.

>

>     Mike

>

>     --------

>     &quot;NO FEAR&quot; -  If you have no fear you did not go as fast

>     as you could have !!!

>

>     Kolb MK-III Xtra, 912-S

>

>

>     Read this topic online here:

>

>     http://forums.matronics.com/viewtopic.php?p=164998#164998

ceengland(at)bellsouth.ne
Guest

Posted: Sat Feb 23, 2008 11:54 am Post subject: The Kolb drop

Dana Hague wrote:

 	  Quote: 	

 At 04:41 AM 2/21/2008, johnjoyes wrote:

> Because of the speed, this could not be a stall.

 Not saying it's what happened, but stall is a function of AOA, not speed.

> I like the idea of VG's and hope to try them out. But in view of my 

> experience, the place to put them first is on the underside of the 

> tailplane just ahead of the elevator.

 If the tailplane had stalled, that might have helped.   But VG's on 

 the tail won't keep the wing from stalling.

 -Dana

 -- 

  Why is it called tourist season if we can't shoot at them?

Actually, loss of elevator effectiveness can be a real problem, either 

from blanking in the wing's turbulence or an actual tail stall. If it 

happens, the wing doesn't stall; it just continues on its existing path 

without increasing its angle of attack. Remember, the elevator is trying 

to push the tail down. If that doesn't happen, the wing's angle of 

attack won't increase.

A real world example is the Cessna Cardinal. The early ones ran out of 

stabilator authority in the landing & couldn't be flared adequately. The 

fix was a leading edge slat on the stabilator that's 'upside down' in 

the stab. Slightly different technique to achieve the same thing as the 

bottom side VG trick: keep the air attached to the low-pressure side of 

the control surface.

http://en.wikipedia.org/wiki/Cessna_177

Charlie

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Sat Feb 23, 2008 5:48 pm Post subject: The Kolb drop

At 02:51 PM 2/23/2008, Charlie England wrote:



 	  Quote: 	
		  Actually, loss of elevator effectiveness can be a real problem, either 

from blanking in the wing's turbulence or an actual tail stall. If it 

happens, the wing doesn't stall; it just continues on its existing path 

without increasing its angle of attack. Remember, the elevator is trying 

to push the tail down. If that doesn't happen, the wing's angle of attack 

won't increase.


	


If the tailplane stalls, I would expect the aircraft to pitch down, no?



 	  Quote: 	
		  A real world example is the Cessna Cardinal. The early ones ran out of 

stabilator authority in the landing & couldn't be flared adequately. The 

fix was a leading edge slat on the stabilator that's 'upside down' in the 

stab. Slightly different technique to achieve the same thing as the bottom 

side VG trick: keep the air attached to the low-pressure side of the 

control surface.


	


DId the Cardinal tailplane actually stall or just "run out of 

authority"?  If it stalled, I would expect it to pitch down, as I said... 

if it simply wasn't effective enough that's different.



-Dana



do not archive

--

  Balance the budget--declare politicians a game species.

slyck(at)frontiernet.net
Guest

Posted: Sat Feb 23, 2008 7:25 pm Post subject: The Kolb drop

From my dim memory the hearsay was that the early Cardinal would get  

stuck in a position on takeoff

where it would just roar off the end of the runway without climbing  

out of ground effect.

Never actually watched it happen. 



They did put those slots on the tail though.

BB

do not archive



On 23, Feb 2008, at 8:42 PM, Dana Hague wrote:



 	  Quote: 	
		   



 At 02:51 PM 2/23/2008, Charlie England wrote:



> Actually, loss of elevator effectiveness can be a real problem,  

> either from blanking in the wing's turbulence or an actual tail  

> stall. If it happens, the wing doesn't stall; it just continues on  

> its existing path without increasing its angle of attack.  

> Remember, the elevator is trying to push the tail down. If that  

> doesn't happen, the wing's angle of attack won't increase.



 If the tailplane stalls, I would expect the aircraft to pitch down,  

 no?



> A real world example is the Cessna Cardinal. The early ones ran  

> out of stabilator authority in the landing & couldn't be flared  

> adequately. The fix was a leading edge slat on the stabilator  

> that's 'upside down' in the stab. Slightly different technique to  

> achieve the same thing as the bottom side VG trick: keep the air  

> attached to the low-pressure side of the control surface.



 DId the Cardinal tailplane actually stall or just "run out of  

 authority"?  If it stalled, I would expect it to pitch down, as I  

 said... if it simply wasn't effective enough that's different.



 -Dana



 do not archive

 --

  Balance the budget--declare politicians a game species.

biglar

Joined: 14 Jan 2006
Posts: 457

Posted: Sat Feb 23, 2008 8:09 pm Post subject: The Kolb drop

Most of it's lost in the hazy mists of antiquity and the Lar's aging 

memory, but 8 or 10 years ago I checked out in a '68 (I think) Cardinal 

that had been upgraded to the horizontal stabilizer slots and I don't 

remember hearing about that one.  Biggest thing the instructor worried 

about was sudden control movements on final approach.  It was very 

touchy and easy to get porpoising on short final - a real attention 

getter - but, with a gentle, steady touch, it did work.  I MUCH prefer 

the C-172.

Biggest reason I only rented it 3 or 4 times was the awful lack of 

power.  Seems (as I recall) like it had the 150 hp engine, and it had 

less apparent power than a C-150.  With 2 up it took forever to get 

airborne, climb was only 300 or 400 fpm and I always felt like it was 

borderline on a stall.  This one had the original high performance wing, 

too.  Stalls practiced at 3500 feet AGL were scary - it would suddenly 

just quit and drop like a stone.  I was told that the later 180 hp 

versions with the milder wing were very nice to fly.  Wish I could have 

tried one.  Visibility out of the Cardinal was the best of any GA 

aircraft I've flown in.  Entry and exiting the plane were very easy, 

too.  Almost a goodie.                   Lar.                  Do not 

Archive.

robert bean wrote:

 	  Quote: 	

 From my dim memory the hearsay was that the early Cardinal would get 

 stuck in a position on takeoff

 where it would just roar off the end of the runway without climbing 

 out of ground effect.

 Never actually watched it happen. 

 They did put those slots on the tail though.

 BB

 do not archive

 On 23, Feb 2008, at 8:42 PM, Dana Hague wrote:

> 

>

> At 02:51 PM 2/23/2008, Charlie England wrote:

>

>> Actually, loss of elevator effectiveness can be a real problem, 

>> either from blanking in the wing's turbulence or an actual tail 

>> stall. If it happens, the wing doesn't stall; it just continues on 

>> its existing path without increasing its angle of attack. Remember, 

>> the elevator is trying to push the tail down. If that doesn't 

>> happen, the wing's angle of attack won't increase.

>

> If the tailplane stalls, I would expect the aircraft to pitch down, no?

>

>> A real world example is the Cessna Cardinal. The early ones ran out 

>> of stabilator authority in the landing & couldn't be flared 

>> adequately. The fix was a leading edge slat on the stabilator that's 

>> 'upside down' in the stab. Slightly different technique to achieve 

>> the same thing as the bottom side VG trick: keep the air attached to 

>> the low-pressure side of the control surface.

>

> DId the Cardinal tailplane actually stall or just "run out of 

> authority"?  If it stalled, I would expect it to pitch down, as I 

> said... if it simply wasn't effective enough that's different.

>

> -Dana

>

> do not archive

> -- 

>  Balance the budget--declare politicians a game species.

-- 

Larry Bourne

Santa Fe, NM

Building Kolb Mk III

"Vamoose"

www.gogittum.com

www.gogittum.com/blog

_________________
Larry Bourne
Palm Springs, CA
Building Kolb Mk IIIC
"Vamoose"

pj.ladd(at)btinternet.com
Guest

Posted: Sun Feb 24, 2008 3:07 am Post subject: The Kolb drop

the wing doesn't stall; it just continues on  its existing path without 

increasing its angle of attack. Remember, the elevator is trying to push the 

tail down. If that doesn't  happen, the wing's angle of attack won't 

increase>>



Hi,

It will as the speed drops off.  The angle of attack may remain constant in 

relation to the ground but NOT in relation to the airflow. As the plane 

slows and begins to sink the Apparent wind will come increasingly from below 

and the wing will stall.



Cheers



Pat.

ceengland(at)bellsouth.ne
Guest

Posted: Sun Feb 24, 2008 7:29 am Post subject: The Kolb drop

pj.ladd wrote:

 	  Quote: 	
		   



 the wing doesn't stall; it just continues on  its existing path 

 without increasing its angle of attack. Remember, the elevator is 

 trying to push the tail down. If that doesn't  happen, the wing's 

 angle of attack won't increase>>



 Hi,

 It will as the speed drops off.  The angle of attack may remain 

 constant in relation to the ground but NOT in relation to the airflow. 

 As the plane slows and begins to sink the Apparent wind will come 

 increasingly from below and the wing will stall.



 Cheers



 Pat. 


	


I believe that the original post referred to diving toward the ground & 

getting no elevator response when he attempted to flair, & blamed it on 

the tail being ineffective because it was in disturbed air. If that 

happened, the wing wouldn't have increased its angle of attack. If the 

tail never forces a change in the wing's angle of attack, the plane 

won't slow down until it hits something. It will just attempt to 

maintain trimmed airspeed by pitching down. A high thrust line pusher 

would be different since pulling power effectively changes trim, but 

didn't the original post say he was descending power off?



Charlie

pj.ladd(at)btinternet.com
Guest

Posted: Mon Feb 25, 2008 7:37 am Post subject: The Kolb drop

Hi Charlie

the plane won't slow down until it hits something.>>



That will do ut every time.



Pat

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