Flutter Investigated In Loss Of Grob SPn Utility Jet

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Last November's crash of a Grob SPn Utility Jet prototype may have involved aerodynamic flutter in the aircraft's horizontal tail. Germany's Federal Bureau of Aircraft Accidents Investigation (BFU) is looking at that scenario as a likely cause of the Nov. 29 crash of the company's second light-jet prototype. Grob chief test pilot Gerard Guillaumaud, 45, a former French air force pilot and a graduate of the National Test Pilot School in Mojave, Calif., died in the crash. He was the airplane's sole occupant. The crash occurred shortly after takeoff, as Guillaumaud reportedly brought the jet around for a high-speed pass as a demonstration to potential customers. Reports indicate the BFU's investigation located parts from the tail as much as 400 meters from the main wreckage.

The accident aircraft had first flown two months earlier, accumulating only 40 cycles and 28 flight hours before the crash. Larger control surfaces -- including ailerons -- had been fitted to the prototype before the accident flight but had not been tested throughout the SPn's flight envelope. It's not known to what role, if any, the lack of testing or the larger surfaces themselves played in the crash. As AVweb previously reported, Grob is moving ahead with plans to certify and market the SPn Utility Jet in early 2008, about six months later than originally planned.