JetPilot
Joined: 10 Jan 2006
Posts: 1246
|
 Posted: Thu Sep 03, 2009 7:15 pm Post subject: Tail Wire Tangs Breaking And other Tail Brace Issue Continue |
 |
|
Given the recent very close call by one of our fellow Kolb flyers, this issue needs to be brought to everyones attention. I wonder if Jimmy Young knows how close to death he was on his last flight with a cracked tang ? Fortunately, Jimmy did a good preflight and caught the problem before it killed him. Kolbs have a single set of tail brace wires, this was done for easy folding of the tail but also has the disadvantage of being very dangerous. With a single set of tail wires, any breakage is most likely to be fatal. Almost all airplanes built, including ultralight type planes have a dual set of tail brace wires, this is considered good design and is done for a couple important reasons, the most important being that if one wire or tang fails the tail will not collapse and will give the pilot a really good chance of keeping control of his plane and landing safely.
In professional aviation and the airlines, the absence of accidents does not mean that there is not a large danger. Reports of problems, and many near accidents is regarded as an accident waiting to happen, and these problems are fixed before people get killed. We have a pattern like this developing with our Kolb Tail wires. Over the years, there have been reports of Tail wires coming loose, or very nearly so, resulting in some very near accidents. Last year, Rans put out an AD on their tail wire tangs ( See Attachment ) for many reported cases of cracks and even complete breakages, the same Tangs many of our Kolbs use. Luckily, Rans aircraft have dual tail brace wires, our Kolbs do not. I posted on this subject last year, and problems continue. Last week, Jimmy Young found one of his tangs had broken half way through, and was VERY close to failing totally, had his last flight been longer, there is a good chance he would have had a totally uncontrollable, tumbling airplane and would have crashed. The other problem area that has been cropping up from time to time is that the removable bolt that holds the tail tangs at the bottom of the rudder has come loose for various reasons on several occasions. There are several reasons that this happens, but the important point here is that despite everyones best efforts, IT HAPPENS... Tail wires also corrode and break over time, it has happened many times on other aircraft models.
Having followed this problem over the years, last month I finally modified my MK III Xtra to have dual tail brace wires, something I have wanted to do for a long time. I attached the wires at the same distance out on the tail as the original tail wires, and made the bottom attachment totally independent from the original set of wires so as not to induce any single point that can fail. The tail tubes on a Kolb have inserts where the tang bolts go through to strengthen the tail at these attachment points. Not wanting to take my tail completely apart, I used larger sized tubing and put the sleeves on the outside of the original tubes. I also used Aircraft structural epoxy so that these doublers would stay very tightly attached to the tail structure, see pictures. The result of this modification is that my tail will stay in place and flyable in the case of any tang, or wire breaking. Several Kolbs on the list have this modification, and it is a really good idea. Doing this modification and repairing and patching the fabric after the fact is not beautiful, the doublers do stick out of the tail tubes a bit, but safety is far more important to me than having a perfect finish. If you do not want to, or are not capable of doing this modification to your, you should inspect these tangs per the RANS AD attached, and keep your tail brace wires in new condition.
As always, modifications to existing designs are purely experimental and can be deadly if not engineered and constructed correctly. Do not attempt a modification like this without doing the research, and getting expert help if necessary.
Mike
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kolb-List |
|
| Description: |
| Bottom attach point for tail wires. Note seperate bolts and tangs for each set. |
|
| Filesize: |
461.04 KB |
| Viewed: |
1352 Time(s) |
|
| Description: |
| Completed second set of tail wires. |
|
| Filesize: |
456.8 KB |
| Viewed: |
1352 Time(s) |
|
| Description: |
| Tail Tube Doublers being glued in place with Aircraft Structural Epoxy. |
|
| Filesize: |
251.66 KB |
| Viewed: |
1352 Time(s) |
|
| Description: |
| External Tube Brace, larger sized tube cut in half and fit over tubes in tail at cable attach points. |
|
| Filesize: |
246.63 KB |
| Viewed: |
1352 Time(s) |
|
| Description: |
| Jimmy Young's Broken Tang, it was very close to complete failure. |
|
| Filesize: |
153.55 KB |
| Viewed: |
1352 Time(s) |
|
| Description: |
| Tang AD and inspection procedure in PDF format. IMPORTANT !!! |
|
Download |
| Filename: |
TangTailWireAD.pdf |
| Filesize: |
77.69 KB |
| Downloaded: |
175 Time(s) |
_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!
Kolb MK-III Xtra, 912-S |
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
