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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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 Posted: Sun Mar 27, 2016 4:59 pm Post subject: Wing Twist, Aileron Reversal, Testing to Destruction |
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I'm getting cold and it is getting dark. So if I don't make a lot of sense and make a lot of typos, please forgive. When I get home to my computer, I'll try to do a better job.
The early Ultrastars had a wing twist problem. When activating those big barn door full span ailerons, the wing would twist in the opposite direction and cancel out the input. That was because the the main spar wing attachment was two small 4130 tubes attached inside the spar, top and bottom. Not a good idea. This US wing had the same problem the B-47 had, as related to me by a B-47 pilot, Dave Thomas RIP after relating to him my experience with my first homebuilt, the early US. The wing universal joint was on the front. Soon a modification was made to eliminate this problem, the 4130 collar and the universal was moved to the rear attach point. No more twist.
The ailerons will not reverse control on a Kolb. The Kit Fox and its predecessor (CRS) had that potential problem if the aileron control linkage was not adjusted correctly. My buddy, Junk Yard Chuck Shaunesy, put one in the pine trees upside down when this happened to him.
You can literally put a Kolb on its wing tip in a very tight turn. Looks like the wing tip is stuck on one spot on the ground. Not 90 degrees, but very close to it. I have demonstrated this maneuver many times in my MKIII and the factory FS at the Kolb Homecomings and many other places over the years. When you want to level out, right stick and it rolls back level.
Kolb ailerons and elevators are hanging on their hinges by their leading edges. About as unbalanced as I am. I experienced aileron flutter on my US, FS, and MKIII. In the MKIII anything over 80 mph and it was prone to flutter. Homer Kolb and the rest of the Kolb crew did not believe me when I told them all my Kolbs experienced flutter. I designed counterbalance weights for the MKIII when I built it. Early on in testing it fluttered. My counterbalance weights were actually aggravating the problem. I flew down to Sun and Fun, 1993, to fly the factory MKIII. Dick Rahill was flying the factory FS as usual. He had been over to South Lakeland screwing off and had to stay until after the air show. A typical Lakeland thunderstorm was brewing and the wind was starting to kick ass when Dick departed South Lakeland. He was flying wide open, about half way back, hit some severe turbulence, and the FS went into severe flutter. Definitely got Dick's attention. He was white as a sheet when he landed. Within a week or two I had a set of FS counterbalance weights for my MKIII. They were not quite heavy enough, but I figured out how to make them work. Never had a hint of flutter since then. Kolb Company finally figured out we had a flutter problem and reacted very quickly. If your Kolb does not have aileron counter balance weights, it should have. I flew a lot of Kolbs that did not flutter. Never had a elevator flutter, but have had rudder flutter on FS and MKIII. My fix for the MKIII was double up on rudder pedal springs. It works. I can fly with my feet on the deck.
Dennis Souder and Homer decided to test the Ultrastar by flying rather than static load test. The US was equipped with an accelerometer (G Meter) and a Jim Handbury, hand deployed parachute. Dennis' test consisted of diving for airspeed and pulling out to load the wings. BTW all Kolbs are rated at 4 Gs + and -. Several tests to 4 Gs was completed satisfactorily. Dennis decided to do a final test a little (lot) faster with an abrupt pull out. I can not remember the numbers, but when he snatched the stick back the left drag strut failed by bending out of column. Dennis tossed the parachute and recovered himself and the US. They immediately designed a drag strut brace that solved the problem.
The reason the newer model MKIII has a near center mounted aileron horn is the use of a Morse Control Cable, rather than the normal push/pull tube configuration on the older Kolbs.
I am sure there is some twist in the inboard aileron horn mounted front spar, but it is negligible.
Lack of aft stick with heavy loads is caused by the use of 3/32 up elevator cables. When I built my MKIII 25 years ago, I installed 1/8" up and 3/32 down cables. I don't have that problem. I think Kolb went to 1/8" up elevator cables after the first year we had the new yellow MKIII at Lakeland. I had to abort a takeoff with a rather hefty passenger when I ran out of aft stick. I had an idea it was going to do this and informed my passenger prior to takeoff, if I was not flying by midfield, I would abort. The light bulb went off, I put two and two together. Bryan put 1/8" up elevator cable on the MKIII and solved problem.
About all I can think of now. Got to go tend my frost bit fingers.
john h
mkIII
Titus, Alabama
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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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Herbgh(at)nctc.com
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| Posted: Sun Mar 27, 2016 5:22 pm Post subject: Wing Twist, Aileron Reversal, Testing to Destruction |
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Everything I wanted to hear...thanks Heaps... with my memory you have
likely said most of it before...Good to hear...Herb
On 03/27/2016 07:58 PM, jhauck(at)elmore.rr.com wrote:
| Quote: |
I'm getting cold and it is getting dark. So if I don't make a lot of sense and make a lot of typos, please forgive. When I get home to my computer, I'll try to do a better job.
The early Ultrastars had a wing twist problem. When activating those big barn door full span ailerons, the wing would twist in the opposite direction and cancel out the input. That was because the the main spar wing attachment was two small 4130 tubes attached inside the spar, top and bottom. Not a good idea. This US wing had the same problem the B-47 had, as related to me by a B-47 pilot, Dave Thomas RIP after relating to him my experience with my first homebuilt, the early US. The wing universal joint was on the front. Soon a modification was made to eliminate this problem, the 4130 collar and the universal was moved to the rear attach point. No more twist.
The ailerons will not reverse control on a Kolb. The Kit Fox and its predecessor (CRS) had that potential problem if the aileron control linkage was not adjusted correctly. My buddy, Junk Yard Chuck Shaunesy, put one in the pine trees upside down when this happened to him.
You can literally put a Kolb on its wing tip in a very tight turn. Looks like the wing tip is stuck on one spot on the ground. Not 90 degrees, but very close to it. I have demonstrated this maneuver many times in my MKIII and the factory FS at the Kolb Homecomings and many other places over the years. When you want to level out, right stick and it rolls back level.
Kolb ailerons and elevators are hanging on their hinges by their leading edges. About as unbalanced as I am. I experienced aileron flutter on my US, FS, and MKIII. In the MKIII anything over 80 mph and it was prone to flutter. Homer Kolb and the rest of the Kolb crew did not believe me when I told them all my Kolbs experienced flutter. I designed counterbalance weights for the MKIII when I built it. Early on in testing it fluttered. My counterbalance weights were actually aggravating the problem. I flew down to Sun and Fun, 1993, to fly the factory MKIII. Dick Rahill was flying the factory FS as usual. He had been over to South Lakeland screwing off and had to stay until after the air show. A typical Lakeland thunderstorm was brewing and the wind was starting to kick ass when Dick departed South Lakeland. He was flying wide open, about half way back, hit some severe turbulence, and the FS went into severe flutter. Definitely got Dick's attention. He was white as!
a sheet when he landed. Within a week or two I had a set of FS counterbalance weights for my MKIII. They were not quite heavy enough, but I figured out how to make them work. Never had a hint of flutter since then. Kolb Company finally figured out we had a flutter problem and reacted very quickly. If your Kolb does not have aileron counter balance weights, it should have. I flew a lot of Kolbs that did not flutter. Never had a elevator flutter, but have had rudder flutter on FS and MKIII. My fix for the MKIII was double up on rudder pedal springs. It works. I can fly with my feet on the deck.
Dennis Souder and Homer decided to test the Ultrastar by flying rather than static load test. The US was equipped with an accelerometer (G Meter) and a Jim Handbury, hand deployed parachute. Dennis' test consisted of diving for airspeed and pulling out to load the wings. BTW all Kolbs are rated at 4 Gs + and -. Several tests to 4 Gs was completed satisfactorily. Dennis decided to do a final test a little (lot) faster with an abrupt pull out. I can not remember the numbers, but when he snatched the stick back the left drag strut failed by bending out of column. Dennis tossed the parachute and recovered himself and the US. They immediately designed a drag strut brace that solved the problem.
The reason the newer model MKIII has a near center mounted aileron horn is the use of a Morse Control Cable, rather than the normal push/pull tube configuration on the older Kolbs.
I am sure there is some twist in the inboard aileron horn mounted front spar, but it is negligible.
Lack of aft stick with heavy loads is caused by the use of 3/32 up elevator cables. When I built my MKIII 25 years ago, I installed 1/8" up and 3/32 down cables. I don't have that problem. I think Kolb went to 1/8" up elevator cables after the first year we had the new yellow MKIII at Lakeland. I had to abort a takeoff with a rather hefty passenger when I ran out of aft stick. I had an idea it was going to do this and informed my passenger prior to takeoff, if I was not flying by midfield, I would abort. The light bulb went off, I put two and two together. Bryan put 1/8" up elevator cable on the MKIII and solved problem.
About all I can think of now. Got to go tend my frost bit fingers.
john h
mkIII
Titus, Alabama
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Signature text; Fort Marcy Park? Sure...Mr. Foster...Third red light and turn left.
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