Taylorcraft Struts Vs Zodiac 601XL deaths

[gnflyn]

O.K. Lets see here:

1. The FAA calls an emergency strut AD on 5000 plus (?) Taylorcrafts that have never suffered an inflight strut failure. This AD instigated by a parts supplier who just happens to want to sell struts...

2. The FAA is stating "no immediate plans to call for grounding the Zodiac 601XL", as of today. This action in response to the NTSB urgent request to ground all 601XL aircarft immediately. This request as a result of the 6 crashes in 2 years resulting in 10 deaths here in the US, as well as a number overseas. This from a fleet of several hundred in 2 years. Again, the NTSB has asked for grounding of all 601XL aircraft immediately due to these crashes...

Please see the following for more information:

http://www.avweb.com/avwebflash/news/NTSBAsksFAAToImmediatelyGroundZodiacCH601XLAircraft_200157-1.html

Hmmm, I must fail to see something here??? Is my information not valid??

[1938BF50]

Re: Taylorcraft Struts Vs Zodiac 601XL deaths

What timing.....

We rec'd an update on this issue at last nights EAA Chapter 93 meeting. Flutter is the issue. One of our members is building a 601XL and is very in tune with happenings. His update praises the NTSB as acting in a very professional manner concerning this grounding request. He says the NTSB has been deeply involved with the type club, individual builders test techniques, and submission of data for review.

FAA take notice......

[N96337]

Re: Taylorcraft Struts Vs Zodiac 601XL deaths

That's the joys of it being experimental....if it was type certificated, they'd have more control....but then again, it'd never get into production because of all the hoops and red tape in the first place......
JH

[VictorBravo]

Re: Taylorcraft Struts Vs Zodiac 601XL deaths

We had a 601XL crash here on the first flight, it was built by members of our EAA chapter 40. Shortly before the first flight, three or four of us went out to the final assembly hangar off-site and looked at the airplane. We found several major and minor problems, advised the builder, and told him not to fly the airplane himself on the first flight, and I personally asked him to not fly it from that airport because there were less options. Sure enough, he flew it anyway, and when the engine failed at the wrong time, he panicked and put it into a nearby house. Walked away nearly unscathed, only from the grace of the Good Lord above.

The things we found on the airplane on that visit are worth mentioning here. There were several general workmanship problems and "no, you can't tie the electrical wiring directly to the exhaust pipe" kind of stuff.

Some of the other things, however, were of concern from a design and kit standpoint. Because the instruction manual never told him to do a final tightening and security check on the aileron control attach nuts someplace, he never tightened them fully. You could grab one end of the horizontal stabilizer and move it fore and aft a couple of inches, and watch the tall, unsupported stabilizer attach tabs twist a little bit to allow this motion. There were other parts on the airplane that also raised a few eyebrows. My point is there were a few things on that design which did not seem sturdy enough, or instructions that were foolproof enough, for a marginally educated builder like Paul

We have another 601XL builder who is working in our chapter hangar now, and fortunately he has more mechanical education than the previous one. But I personally noticed some things...

The 601XL ailerons are huge, lightweight, and hinged at the front. The first thing I thought about was flutter. I asked the builder when the balance counterweight gets put on, and he said there is none needed on this design.

I beg to differ.

I will put my balls on the block publicly here, and say that I believe Chris Heintz was struggling with these issues, and that he was trying too hard to get the airplane under the LSA weight limit. When Dick Van Grunsven comes out and says that it was a huge struggle to get the RV-12 built safely under the weight limit, that should make you take notice. Heintz is a highly qualified engineer, and not an idiot. I'll bet that extra five pounds of lead weight that should have been used as an external mass balance under the ailerons is something he reluctantly gave up to use that weight somewhere else in the structure. I have no way of knowing this for sure, it's only my guess.

The latest I heard from an educated XL builder was that Zenair (Heintz) feels that more tension on the aileron cable circuit will solve the problem. My personal feeling is that this is a Band-Aid fix. If the ailerons are flutter-prone with too little tension, they will still be flutter-prone with more tension, but the extra tension will be holding the tendency to flutter in check.

Assuming the aileron itself is rigid enough to resist torsional flexing, it would seem that the right thing to do is to put a balance weight on the aileron. This will increase the empty weight of the aircraft by five or ten pounds, but that is a small price to pay.

I went on one of the Zenith airplane boards several months ago, after one of the crashes and BEFORE they knew this was flutter related. I made a statement that all owners should self-impose a reduction in smooth and rough air speeds of 20% until this matter was sorted out. Now that flutter is strongly emerging as the culprit, maybe some of those yahoos will take back some of the flaming they dished out.

The 601 is not a bad design IMHO, but it is marginal because of the LSA weight limit. LSA was based on European limits, which were based partly on European sized people. For a designer to offer a product to the USA market, they must address the fact that a higher percentage of the gross weight will be taken up by fat American asses, leaving less for the structure. The plastic airplanes can easily achieve this using carbon and glass. But the metal airplanes are a challenge!

[NY86]

Re: Taylorcraft Struts Vs Zodiac 601XL deaths

Not to defend the AD, but, there's a big difference between issuing an emergency AD with a corrective action and grounding a fleet for an indeterminent length of time. Anyone remember the V-tail Bonanza fiasco?

[Len Petterson]

Re: Taylorcraft Struts Vs Zodiac 601XL deaths

Acording to EAA's website the 601 XL is NOT grounded. Also the manefacturer claimes extensive flutter teasting has been dune in Europa in different places and no flutter was found. Read more on EAA's website.

Weight limits are making tradeoffs is something I can understand and appriciate, and if you then through in the price if high strenght ,low weight materials! OPPS! We no longer was an affordable aircraft.
Len

[VictorBravo]

Re: Taylorcraft Struts Vs Zodiac 601XL deaths

You are correct, the 601XL is not officially grounded by the FAA. The NTSB has issued a strong recommendation to ground it, and it is surprising that the FAA has not done so.

I had a conversation with an aero engineer this weekend, and he verified what I already knew. To solve flutter, you DON'T just tighten the cables to postpone it, you make the aileron NOT WANT to flutter in the first place. Any half-assed amateur like me knows what has to be done here, and the trained engineers like Heintz know what has to be done too. The ailerons need to be mass balanced (and likely the elevator too).

Unfortunately it will be seen up as an admission by Heintz that the design had a flaw originally, which makes him look bad. Just saying that "too many builders had cables loose... better snug 'em up some" doesn't make him look bad.