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#1
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I was recently made aware that some here have questions about the AD issued on Aviation Enterprises regarding extended wing tips and whether Flint Aero will also be affected. There will be an AD forthcoming dealing with our wing tips as well and we are currently working with the FAA and the Small Aircraft Directorate on this matter. The incident in Farmington, New Jersey prompted the FAA and the SAD to look into not only AE's modification but Flint Aero's as well (based on one Service Difficulty Report on a Flint modified T337G that reported some wing skin cracks at WS150 underneath the removable fuel tank access cover). I have had an engineer working on this project for the last few months and the engineering study has been quite intense. The FAA was able to get engineering data directly from Cessna though that information could not be shared with us. We have had to reverse engineer the wing which has taken quite some time.
To deal with this upcoming AD we are looking at two options. One would be a structural reinforcement while the other would involve reworking the limitation for “zero fuel” in the tip tanks. The current limitation is the requirement of maintaining at least 12 gallons of fuel in each tip until the aircraft gross weight reaches 4,330 lbs. This limitation has been in place from the time the STC was first issued in 1991. It is possible that the "fix" will include a combination of the two options. The structural reinforcement will be relatively non-intrusive and includes reinforcing the stringer splice at WS150 and some externally mounted stainless steel straps on three stringers and the forward spar cap outboard of WS150. At WS150 there will be two bands of SS attached chordwise. One band will be 3.5” x 19.75” and will be riveted to the underside of the removable fuel panel and will attach at the existing screw locations at WS150. A second band (5” x 19.75”) will be riveted to the exterior of the upper skin and will also attach at WS150 via the existing screw locations. The stringer straps will be 1” wide and begin 2" outboard of WS150 and terminate 3" outboard of WS177. The spar doubler (also 1” wide) will originate at WS162 and terminate at WS192. These reinforcements will be required only on the upper wing surface. Of course, this “fix” will first have to be approved by the FAA though so far they have been very happy with the data we have supplied. Please note that the plans for the structural reinforcement is preliminary and may change as we continue to refine our data. The limitation option is still one we are looking at. We believe the aircraft is fine at 4,330 lbs with a minimum of 12 gallons in each tip. At higher weights we believe that there would need to be more than 12 gallons in each tip. Right now I would error on the side of caution and recommend keeping the tips tanks full until the gross weight drops to 4,330 lbs and then begin transferring fuel from the tips to the mains. We are still working on what the “zero fuel” weight would be but we feel the weight of 3,300 lbs that is listed in the AD which affects Aviation Enterprises is much lower than it needs to be. Right now, though, I would recommend keeping a minimum of 12 gallons in each tip at all times (or at least when the gross weight is above 3,300 lbs) until we finalize the "zero fuel" weight. The limitation option may not be practical in the long term though it would at least be a required temporary limitation until the aircraft is reinforced. This AD will only affect 337s that do not have the 150.6 gallon capacity factory fuel tanks, what we refer to as the “long wing” aircraft. The wing structure of the “long wing” is stronger than the “short wing” aircraft. I would note that the aircraft involved in the New Jersey incident as well as the one in the recent Avon Park incident were "short wing" aircraft. I think we are all aware that the pilots involved in the New Jersey incident were asking a lot of the airframe. The FAA quickly issued a SAIB (CE-10-20) though the response to that SAIB was tepid in their view. Flint Aero was included in that SAIB. The latest incident in Avon Park, Florida has the FAA additionally concerned because the wing failure occurred in the same general area (perhaps a bit inboard) though this aircraft did not have wing tip extensions. I do not know if this latest incident will have an effect on the upcoming AD for Flint Aero but they did contact me for some input. I do appreciate Larry for allowing me to use this forum to get some information out. If anyone has any questions feel free to contact me via phone (619-448-1551), e-mail (Dennis@flintaero.com) or here in this thread. Dennis Hamblin President, Flint Aero, Inc. Last edited by Denhamblin : 12-02-10 at 07:26 PM. 
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#4
12-02-10, 08:25 PM
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Did you mean the one from the Flint guy?
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Gord C-FTES
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#6
12-02-10, 08:58 PM
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Dennis
We appreciate the comments made by anyone who has any involvement with Skymasters.
Thank you for sharing with us. A couple of comments, questions. First, The New Jersey accident, I thought, involved a Super Skyrocket, a pressurized airplane. I would have assumed that it had the strengthened wing. Do you mean that all pressurized Skymasters don't have the same strengthened wing?? In other words, they are not all created equal. Second, the straps on top of the wing are only for those aircraft that do not have the 150 gallon capacity wing, and have Flint tanks? Do aircraft that do not have the 150 gallon wing, and don't have Flint tanks going to need this reinforcement? I have seen on other types of aircraft, a need for a spar inspection. This frequent, and frequently expensive inspection is waived, if there is a spar replacement. Would not a spar replacement, incorporating spar used in the stronger wing, be a better solution than straps on top of the wing?? Thank you,
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#7
12-03-10, 01:03 AM
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Quote:
The upcoming AD for aircraft modified with Flint Aero extended wing tip fuel tanks will only be for "short wing" 337s modified with Flint Aero extended wing tip fuel tanks as far as we can tell right now. Until the FAA signs off on our findings we can only speculate but I can say that I am very comfortable with the work of my engineer and the feedback I have received from the FAA on our preliminary findings.If you don't have the Flint Aero tips you would not be effected by this AD. If you have wing tip extensions manufactured by Aviation Enterprises you would be required to follow the instructions in that AD. However, the accident in Avon Park may bring into question the non-modified 337 wing. Since the accident in New Jersey the focus has been only on 337s with extended wing tips. A replacement of the spar will not be required in addressing the issues incorporated in the forthcoming AD for 337s modified with Flint Aero tip tanks. There may be other ways to address the issue but we think our solution is one that addresses the issue in the most economically feasible way. According to my engineer, and he has been in this trade for many years, this has been done before on other aircraft. Last edited by Denhamblin : 12-03-10 at 01:06 AM.
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#8
12-02-10, 09:09 PM
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It's all that cold weather up here. I thought he might be kidding. Thank you Larry for letting me be a part of this forum and this website. It is such a good feeling to know that I am not alone. I use my plane only for personal use and humanitarian missions. In January we were part of the Haiti airlift with Bahamas Habitat and when the weather permits we do Hope Air missions flying kids who need non urgent medical treatment from the near north down to Toronto.
The Skymaster is a great aircraft and I hope to be able to fly mine for a long time. It's unfortunate for everyone involved that this happened. All I am looking for is the cost to repair my plane not one red cent more. Thanks again
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Gord C-FTES
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#9
12-15-10, 06:44 PM
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Here we go
Well, here we go. It appears Aviation Enterprises, though guilty of creating an unsafe condition and I quote from the AD 2010-21-18
"Unsafe Condition This AD was prompted by a wing overload failure and by reports of cracks in the upper wing skins on certain Cessna airplanes that are now or have ever been modified by Aviation Enterprises STC SA02055AT, SA02056AT, SA02307AT, or SA02308AT. We are issuing this AD to detect and correct damage in the wings and to prevent overload failure of the wing due to the installation of the STCs. Damage in the wing or overload failure of the wing could result in structural failure of the wing, which could result in a loss of control. At first they were willing to accept responsibility. Then they asked for proof that the work was done. Then they wanted all the engineering data (I speculate so they could copy it and use it to create a fix for the remaining aircraft) and finally they finished off by asking me for the "weight and balance for every flight since the STC was done". Of course that information does not exist. Instead of doing the right thing they have decided to hide and hope that myself and the other aircraft owners will just go away. Well, I can't speak for the others but I can tell you right now that I will not go away until I am reimbursed for the damage caused. I have availed myself to one of the legal firms that my company uses in Tennessee and I will be litigating. They did over $21,000 damage to my aircraft. When I am finished I am told the cost to them including legal fees and damages will approach or exceed $100,000. The firm I am using has extensive experience in this area.
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Gord C-FTES Last edited by Gord Tessier : 12-16-10 at 07:17 AM.
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