ACRO E-mail Archive Thread: Fabric problems with Pitts aircraft
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Thread: Fabric problems with Pitts aircraft
Message: Fabric problems with Pitts aircraft
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From: "Sheldon Apsell" <SHELDONA at FS.MICROLOGIC.COM>
Date: Thu, 06 Mar 1997 11:50:33 UTC
March 6, 1997 In my last post regarding the fabric separating in flight on Roy Speeg's S-2B, I implied that the problem was with the fabric itself and that there should be less of a problem with aircraft covered with dacron (such as Roy's) than with aircraft covered with cotton (such as mine). I have since learned that this is probably incorrect. Although in the past there has been a problem with the quality of fabric on Pitts aircraft, this probably has nothing to do with the incident involving Roy's plane. I have been told that the process by which the dacron is glued to the wing is very critical. Apparently, the adhesive used does not adhere to dacron. Consequently, the adhesive must be applied to the top of the material and then carefully worked through the weave until it comes out the bottom. The glue on the bottom adheres to the wing members, but if there is insufficient glue on the top of the dacron or if it has been applied incorrectly, the fabric will separate from the glue. It is the glue on the top adhering to the glue on the bottom that traps the dacron and keeps it in place. A fabric punch test will tell you whether or not the material is good but it doesn't tell you that it has been properly installed. I don't have any idea what kind of test (if any) can be performed to confirm that the fabric has been properly installed. I would like to emphasize that this can be a very serious problem. It is believed that this is the failure mechanism that led to the fatal crash that killed Steve Wittman and his wife. According to the accident report, Steve did not use the correct procedure for installing the fabric. It then separated in flight causing aileron flutter and structural failure. Another point to consider regards the appropriate course of action to take should you experience such a failure in flight. After the incident with Roy's plane, he asked me why I didn't bail out. The truth of the matter is that it never occurred to me. Although I was wearing my own parachute which I new to be perfect shape, a high quality crash helmet, and long pants (in spite of the Florida heat and humidity); I was psychology unprepared to use my emergency equipment. (I was also right over a pond where earlier in the day Roy and Mike Goulian had been feeding the alligators!) I was lucky in that the fabric separated in an area that did not affect the function of the ailerons. But I now believe that if the fabric has separated further outboard the correct response would have been to bail out immediately (and take my chances with the alligators). Sheldon Apsell Newton, MA Pitts S-2B P.S. There is absolutely no truth to the rumor that Roy is recovering his wing with alligator skins!