Ed.
You are right when you warn: "Make SURE your control surfaces are within spec!" I experienced aileron flutter myself that I could trace to a worn outer hinge of the right aileron. I totally agree with you that we should not allow excessive play in the controls. To assist the mechanics or owners on what to look after read the article on Ercoupe.info. http://www.ercoupe.info/?n=Main.Controls But the flutter I experienced was a high vibration that moved the aileron up and down maybe 1/8th of an inch but in a high frequency and very hard, so it sounded and felt like someone is hammering on your wing with an air hammer. The Sebring eyewitness account reads different. "From the second witness's position, he could see both ailerons - the hinged flaps on the control surfaces attached to the wing's trailing edge - fluttering at a high frequency." This statement makes me rethink my previous assumption of the spar failing first due to overload. The sequence might have been different. Aileron flutter as Ed and I experienced it happens on one surface only. Here we have BOTH ailerons fluttering. And they flutter that much that a witness from 1200ft below can see them moving. That means this was not the flutter due to looseness in the controls hardware. This was a flutter of completely loose ailerons. If the connection rod from the steering mast to the aileron/rudder mix quadrant broke off inflight AND the plane had rudder pedals, the aileron would be free to move through the whole range of possible deflection. THAT could be visible from 1200 ft below. Loosing aileron control would explain why the plane banked to the left without any sign of pilot input. The only thing left they had was the elevator control and (maybe) the rudder. The left turn could not be controlled and the pilot maybe pulled up to reduce the speed. Before the plane would stall, the wing already departed. Now the question still remains what broke the spar. It could have been the flutter, but also the sudden pull-up. Maybe both in combination. We should certainly not only focus on the main spar here, but consider the controls as well. Eds prebuy inspection recommends checking the push tubes with an ice pick. maybe not the best method, but something similar should be done to the push rods every now a nd then. In addition to that one needs to verify that the Heim bearings are good and ones you are at it, replace everything with new fasteners. If that needs to become an AD is not up to me, but it could be amended to AD 2003-21-01. Hartmut To: [email protected] From: [email protected] Date: Mon, 28 Sep 2009 23:25:25 -0500 Subject: RE: [ercoupe-tech] Re;FYI -Seibring crash Read & Ponder Art asked: > Wish we knew what the shiny thing was they saw [departing the aircraft]. Art, Gary Pinnell did an unusually good job of reporting on the accident. I was so impressed I sent complimentary notes to his bosses. Google "Gary Pinnell ercoupe accident" for articles. One of the things mentioned in, I think, the preliminary report was that the majority of the inspection hole covers popped off the aircraft as well as the rear windows. As I recall, they did not pop off simultaneously but were strewn over a distance of the flight path. I'm sure the mechanic thought all was well with the aircraft. My otherwise excellent mechanic thought that about my Ercoupe even though the aileron tightness was out of spec. Fortunately, when I felt the beginning of my aileron flutter, I reacted almost instantly and correctly, loading the ailerons with a roll input to the yoke that stopped the beginning flutter before any damage was done. Heck, my mechanic at that time had done a full Ercoupe restoration as well as many years of Ercoupe annual inspections. But he did not know about Memorandums 56 and 57 I think. Service Memorandums 56 and 57 are NOT in a place that the average mechanic is going to find them during preparation for a normal annual inspection on an unfamiliar aircraft type. They are in the back of the Bulletins and Memorandums book. >From Gary Pinnell's story: http://tinyurl.com/ydf3qu8 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> "Another witness, who was also a certificated airline transport pilot, stated that while outside working on his house he observed the accident airplane flying overhead," Diaz wrote. "He estimated that the airplane was flying at an altitude of about 1,200 feet above ground level, and did not note anything abnormal about its flight path. About 45 minutes after first seeing the airplane, he heard an abnormal engine sound that diverted his attention again back to it." It sounded as if the engine was being "over-sped," the second unnamed witness told Diaz. It was as if the engine was at full power, and the airplane was in a high-speed dive. When the witness looked up, he saw the airplane pitching up and rolling into a steep left bank, and initially thought that the pilot was attempting to perform a "barrel-roll or a slow roll." >From the second witness's position, he could see both ailerons - the hinged flaps on the control surfaces attached to the wing's trailing edge - fluttering at a high frequency. . . . The second witness also reported to Diaz that during the breakup, the airplane released what looked like confetti, which he later determined to be painted chips from the airplane's fabric-covered wings. At Bartow Municipal Airport, 24 nautical miles west, the wind was blowing about 10 mph, and gusting to 16 mph. Portions of wreckage were found along a north-northeast 3,100 feet long path. Both aft cabin windows were found at the southern end of the wreckage path. Paint chips, inspection panels, and personal effects from inside the airplane were located further along. . . . "The first things that came off the plane were the cockpit back windows, which popped out, we'd guess, from vibration or distortion of their frame," said Burkhead, who viewed the NTSB report with fellow Ercoupe pilots. Inspection panels - aluminum discs - started popping from the bottom of the wings and were strewn along the remaining flight path. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< Does this sound like a simple main spar failure to any of you? I have nothing but guesses about the original cause of this failure. I have no idea if the pilot was doing a high speed pass or not. Nevertheless, if aileron flutter starts and you don't act instantly, you'd better be wearing a parachute and good luck even so. I even heard of a plane getting "vibration" at airspeeds as low as around 85. The aileron play was around one INCH! Fixing/replacing the control linkages and doing proper maintenance apparently fixed that plane as the test flight is said to have gone to 144 without problems. Make SURE your control surfaces are within spec! Ed _________________________________________________________________ Show them the way! Add maps and directions to your party invites. http://www.microsoft.com/windows/windowslive/products/events.aspx
