# "The Kolb Quit" bit me in the butt yesterday

Discussion in 'Hangar Flying' started by Victor Bravo, May 29, 2017.

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1. May 29, 2017

### Victor Bravo

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Saturday was a bad day for me. I was in control of a friend's airplane, and it got damaged. Truth be told, in the few minutes before it got damaged, we almost got seriously injured or worse. This story is being presented as a cautionary tale. The older / more experienced pilots here will immediately identify a point where I should have pulled the plug and stopped the accident before it happened. Nobody got hurt, airplane is repairable, but my ego is on life support over at the ER.

"The Kolb Quit" is a slang name that was given to a specific characteristic known on this type airplane. When you get down to 4 or 5 feet AGL, reduce throttle, and get ready to flare and "feel" for the ground, the airplane quits flying and drops in catastrophically.

Here is a short description that I posted on another internet mail list:

----------------
Well Kolbers I am completely humbled and embarrassed.

Because I got distracted by two or three (legitimately serious) things unrelated to the actual landing, I fell victim to the Kolb Quit and **** near wrecked Jimmy's new Mark 3 today.

I flew out to Camarillo in the 172 this morning early, and after some radio equipment issues we were ready to go. Jimmy took off and we headed out away from the ultralight strip. Immediately it was obvious to both of us that there was a somewhat serious control problem. The control force on the ailerons was very heavy, and it took two hands to roll the aircraft to the right. One hand, but heavy, to make a left roll/turn.

I was given control of the aircraft, and experienced this first hand. The roll rate to the right was atrocious and took both hands to accomplish. Pitch control was heavier than I expected but easily controllable.Yaw control was well within the "Reasonable" range.

Jimmy and I made two or three low passes over the ultralight strip, and I was given the task of landing the airplane. The landing pattern at Camarillo UL strip was very tricky and unsafe as far as I am concerned. In order to not fly over a corporate aircraft facility and their outdoor fuel tanks, the base leg of the pattern is flown extremely close in. Base leg is essentially over the approach end of the strip. Left traffic only, at or below 300 AGL.

The first landing was safe, but bouncy. The Kolb Quit dropped us in from about 2 or 3 feet, to my complete surprise. We taxied back to his hangar andtried to fix the aileron problem.

The second takeoff was made, and there was only a small improvement in controlling the aircraft. It still required two hands to roll the aircraft to the right, and this was needed turning a very close-in base leg, with a hard left turn from base to final. Rolling out of this turn required a two handed right aileron input with a very very slow and not positive result. At 50 feet AGL between a large hangar and a tree.

We made a couple of low passes,and Jimmy reminded me I was far too high and fast, so we went around. On the last pass, he thought I was way too slow. I used the speeds and and techniques I would use in a Taylorcraft, but I did not remember the Kolb Quit. Pulling the throttle back to idle on short final, the airplane landed very hard and seriously damaged the right main gear leg. The airplane got out of hand and headed across the runway for a chain link fence. I applied full power to get it away from the ground, but the high thrust line resulted in us screaming across the runway at below fence height. Full back stick was not getting us any higher than below fence height. We finally climbed over the fence with very little room to spare.

Next time around one of the guys was standing in the middle of the runway waving his arms. What could this be? I finally looked out over to the right side of the aircraft, and saw the right main wheel up at eye level. I knew instantly that this was going to result in a "crash landing".

The next time around, I managed to keep it going faster, and put it on the remaining wheel with no Kolb Quit, but it of course settled down on the one wheel..... and the other wingtip, and proceeded to groundloop and bend one of the wing tips.

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

Looking back in hindsight I should have pulled the plug on the entire episode after the first landing, and not flown the second (test flight) at that location. Moving the location to another airport would have allowed me to make better choices in terms of setting up a straight and more manageable landing approach, which would likely have allowed me to land without damaging the aircraft.

The cause of the aeileron control problem has still not been identified.

Last edited: May 29, 2017
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2. May 29, 2017

### cheapracer

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Scary, glad you and your mate are ok VB.

3. May 29, 2017

### THRC12

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Glad you are ok. While I'm not familiar with the flight characteristics of the Kolb, I do know about hard landings!

4. May 29, 2017

### Rockiedog2

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**** VB that's a good one man!!
Look don't feel so bad we all have bad days and s**t gets torn up pretty regular, right? It was just your turn in the barrel man LOL (sorry we have to be able to laugh don't we especially on our bad days). I've torn em up too out of stupidity not fighting a bad airplane. Well, taking off again wasn't too smart was it, you got the analysis right already...there shoulda been something really obvious going on, right? I've run one outa gas that's a lot worse than what you did; yeah there were circumstances but the PIC was the root problem. And Beckett tore my Legal Eagle up and he was a 600 hour Pitts pilot; I already told that story here. He was a good stick all round but he did exactly what I told him not to and pulled the power off 10 feet in the air and tore the left main out from under it and down on the left wing(the LE has the Kolb Quit thing too). How bout try to look at it like your friend put you in the barrel Saturday...and you didn't hurt anybody and all that little stuff that got damaged is easily repairable no big deal.
We're all trained to take this stuff so seriously and I guess rightly so; it would be foolish not to considering how unforgiving flying is. And our ego gets all so tender about our flying; we take great pride in being respected for being "good". But I've tempered all that over the years and since getting outa the professional game. I look at it as this is recreational aviation and yes the safety of people is all important but I've come to consider the simple hardware that I fool with as being expendable. Nothing more important than a motorcycle or jetski(naw, my stuff isn't nice() like Toobuilder has and lotsa you other guys). If I tear it up I'll fix it or scrap it. And the ego thing isn't a factor for me anymore, screw that. All that's liberating and the fun factor goes way up when we can relax about some of these things we take so seriously. Except hurting somebody.

Well that's my idea of that. Don't mind me carry on as usual.

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5. May 29, 2017

### Rockiedog2

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had a thought about the obvious that I know we all realize

>>>the airplane quits flying and drops in catastrophically.

well, actually more correct to say "the PIC lets the airplane quit flying and drop in catastrophically".
Seems like it's always the PIC.

Spencer
Master of the Obvious

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6. May 29, 2017

### BBerson

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I am confused. Do the ailerons move freely on the ground but not in the air?
Perhaps binding under load. Check for spar damage.

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7. May 29, 2017

### FritzW

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I'm glad you guys are okay. Consider the cost to fix the airplane as cheap education. You'll be an expert on what not to do next time.

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8. May 29, 2017

### Vigilant1

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VB,
Thanks for sharing this, it is a cautionary tale we can all take into consideration. I'm glad everyone is okay and that the plane can be put right.

9. May 29, 2017

### stevel

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Your explanation makes much more sense than the bystander comment in the video that Jimmy sent me.

I hope the ego bruising heals quickly.

I'm going to Camarillo to unload all of the BBQ stuff that I took to the Brian Ranch airshow. Is there anything that I can do there or at Whiteman to help out, give me a call (818) 653-2 Niner Fower One. I'll probably be away from the computer for the rest of the day, so any reply here would be missed.

10. May 29, 2017

### Toobuilder

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Dont beat yourself up too bad Bill, it happens to all of us. The good news is that you are unlikely to do this one again, but probably something as equally avoidable. I almost wrecked the Taylorcaft a few weeks ago by fooling around and landing on a small patch of dry lakebed near my house. I used 105% of the available landing area and collected some shrubbery in the tail wires as a result. In that case it was pretty easy to recognize my head was not in the game, but it is not always so obvious.

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11. May 29, 2017

### rbrochey

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Glad you're okay!

12. May 29, 2017

### TFF

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Glad you and your friend are OK.

13. May 29, 2017

### Hephaestus

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Glad you're ok, everyone walked away and you now can say "I learned something from that". That's the truly important aspect.

Those best learning experiences are the ones you'll never forget.

14. May 29, 2017

### clanon

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15. May 29, 2017

### Dana

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There really is no "Kolb quit". But because the Kolbs handle so well, like a larger plane, people forget how light and draggy they are; they have to be flown like an ultralight, and flared very low, like 12". But once you realized there was a problem with roll control, you should have quit then and there.

Distractions are often what triggers it. I bent my Ultrastar once in a similar manner, though not as bad. We were flying from a muddy field, and just as I flared I realized I was going to touch down in a large puddle, so I tried to hold it off, I should have added power and gone around... I missed the puddle but the bottom dropped out and I hit hard, bending the fuselage down tubes. Fortunately I was able to straighten the tubes and weld a split sleeve over the damaged area.

Dana

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16. May 29, 2017

### lurker

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the goal, i think, is to learn from it and go on to make other, better mistakes.

17. May 29, 2017

### Victor Bravo

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The ailerons moved freely on the ground, but there was more friction in the system than I would have preferred. I wrote that off to UL design practices, tubular bushings instead of good bearings, etc.

When we lifted upward on each ailerons with one finger, I told the guys to lift about one pound each, it became much heavier instantly. There's probably far more than one pound of lift force under the ailerons, they're huge.

We put a quart bottle of oil on top of each aileron, and the force was far higher than I thought appropriate.

I didn't even bother to do a gliderp ilot's "positive control check", I knew that would feel like someone installed a control gust or anti-theft lock.

But the force required to move the ailerons under flight load was the smaller problem by far. The fact that you almost couldn't get any roll rate to the right was the big issue that created an unsafe situation. Rolling out of the moderately banked left base to final turn took several seconds, and this was occuring at altitudes of 20-30 feet and maneuvering around obstacles. Nothing that the Red Bull guys don't see every day, but they have 360/sec roll rates.

As usual in 90% of aircraft accidents, three or four various risk factors, and the pilot lit the fuse by not being as conservative as he should have been.

The part that irritates me the most is that the physical environment at that location pushed an otherwise annoying but manageable situation off into the unsafe area. I also did not position this flight in my own head as a "test flight" b ecause the airplane has ~200 hrs on it. If we had been on a dry lake, or in a farm field, or even at another airport with clear approaches, I very strongly believe I would not have been distracted,a nd there is a good chance I would have remembered the "Kolb Quit" ahead of time.

Another factor is that the design of the airplane is far less conservative than what you think of for "ultralights" or LSA's or "suitable for low time pilot". It is a high lift wing, with zero washout or twist in the wing. The leading edge radius is smaller than my C-172, and much smaller than the typical Cub style airplane.

Now I'm going to say something that I cannot say on another internet discussion group, and I'd rather not see this re-posted over there. I do not want to disparage the aircraft design (and by inference its designer). The ailerons are built as a full span torque tube, driven at the root end. The aileron ribs are installed on that torque tube starting at mid span, which means that for the first half of the semi-span there is just the torque tube behind the trailing edge of the wing. It has worked acceptably on numerous Kolb designs.

On this version they wanted to install flaps. So they built the flaps the same way as the ailerons... a torque tube leading edge with ribs attached tot it. The FLAP torque tube is NOT hinged to the trailing edge of the wing, because the AILERON torque tube occupies the space behind the wing TE all the way to the root. So they hinged the flap torque tube directly to the back of the aileron torque tube, which is hinged to the wing TE. As you move the ailerons up and down, the aileron torque tube rotates, taking the entire flap hinge up and down with it.

Let that sink in a minute...

18. May 29, 2017

### TFF

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The Tailwind and Grumman light planes have tq tube inside tq tube. I dont know how stiff a Kolb wing is. Since you are all right and trying to solve the problems that happened, you get a little HBA ribbing. Good thing you held your own, because the hell you would have gotten in the choppergirl thread from this group would be insurmountable. Glad your Ok.

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19. May 29, 2017

### clanon

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Doesn't seem right ...to me...IMHO.

20. May 29, 2017

### BBerson

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The several second rollout isn't usually acceptable. But each homebuilt is different and may have quirks that owners tolerate. If the design was changed in any way it isn't a Kolb.
It really should have a different name.

It could be lost motion in the torque tube.
It could be a torsionally soft wing structure. Can't really diagnose over the Internet.

I would use the main runway.