• Welcome aboard HomebuiltAirplanes.com, your destination for connecting with a thriving community of more than 10,000 active members, all passionate about home-built aviation. Dive into our comprehensive repository of knowledge, exchange technical insights, arrange get-togethers, and trade aircrafts/parts with like-minded enthusiasts. Unearth a wide-ranging collection of general and kit plane aviation subjects, enriched with engaging imagery, in-depth technical manuals, and rare archives.

    For a nominal fee of $99.99/year or $12.99/month, you can immerse yourself in this dynamic community and unparalleled treasure-trove of aviation knowledge.

    Embark on your journey now!

    Click Here to Become a Premium Member and Experience Homebuilt Airplanes to the Fullest!

Safety Alert Kolb 111 Extra Rudder and Tail boom flutter

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

franc

New Member
Joined
Feb 23, 2020
Messages
2
Guys,
We had a serious incident at our club, involving a Kolb 111 Xtra.
The aircraft developed severe rudder and tail boom flutter. This after trying to alleviate very heavy aileron and rudder forces by increasing the lever arm on the aileron control, and by affixing a standard size trim tab on the rudder.

Please see the report below to the Kit Manufacturer, which as yet is unanswered.

I'm an Authorized RAAus aircraft maintainer and inspector and have been asked by the owner to research the cause of this incident
So my question is ; has anyone else suffered this problem?

And as I'm yet to find anything anything wrong with the rigging of the aircraft prior to the accident, I thought it prudent to alert all to this incident.

Franc

To: "[email protected]" <[email protected]>
Cc: Martin Ford <[email protected]>, Martin Ford <[email protected]>

Hi Brian,

This is just to let you know how things went with the Kolb.

We built and attached the new torque tube arm at the front of the torque tube this resulted in very manageable stick pressures and was a real improvement. I flew about 1.5 hours with this new configuration. I was able to trim the aircraft for straight and level and was becoming quite happy with the handling although the roll rate was slower than I would have liked.

On Saturday afternoon there was virtually no wind at all and it was an overcast and calm. I decided to practice some tight circuits to ascertain how it handled when pulling short base and shot finals in a series of touch and goes. The climb performance was always good but I was light on fuel and it really was exceptional. I climbed out at 80MPH to provide a safety margin incase of an engine failure. The take off from the sealed 05 airstrip went well and the subsequent touch and go on the sealed strip went well. The Base and Final legs were tight but very manageable with the new torque tube arm.

On the next touch and go I decided to use the shorter 05 grass strip that is parallel to the sealed strip again the handling on Base and final went well and the touch and go was a non event again climbing out at 80 MPH at a little over 125 feet the aircraft developed severe rudder flutter. (I will go into what witnesses observed later) I immediately reduced throttle and changed attitude the rudder pedals were oscillating rapidly and I could not suppress them. The stick exhibited no signs of flutter or movement. I took my feet off the pedals to see if it would improve, it continued to get worse. I could hear the cables slapping inside the boom. I pulled the throttle hard off and decided to try and put the aircraft back onto the field knowing there was insufficient field remaining. The buffeting in the aircraft continued even at the reduced speed and it really felt like it was going to break up the shaking in the cockpit was quite severe. I managed to get the wheels back on to the ground around 70 Mph due to the steep approach with little open field left in front of me (about 125 feet left before the boundary fence). Standing on both toe brakes as hard a I could I attempted to ground loop to lessen the impact. About 20-25 feet before the fence the applied pressure broke the left hand rudder pedal off at the lower wield. From then on I had no more control until I hit the corner posts of the boundary fence (not that I could have done much in the final 25 feet or so). I hit the boundary fence at about 90 degrees to the original direction of travel. Due to the inertia of the impact my hand inadvertently advanced the throttle I immediately pulled the throttle off again I then went through the shutdown procedures.

Witnesses on the ground said that the rudder was fluttering so severely that the boom was rotating in a circular fashion like a mixmaster and that the rudder and the tail plain was twisting with the rudder flapping.

I have attached photos of the result. It can beset that the impact was significant. The aircraft was severely damaged the engine and propellor did not contact the fence. There are signs of structural stress on the engine mounts (bending of the tubular structure).

Have there been any other reports of rudder flutter in these aircraft? I have been unable to determine what caused the flutter.

Aside from a bruising from the seatbelts and a bruised finger I am none the worse for wear… More than I can say for the aircraft.
1593355675921.png
1593355716206.png
1593355776008.png
1593355823253.png
1593355853368.png
 
Back
Top