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Bad Vibrations

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Key Takeaways:

  • The Grob G115D accident was attributed to an inflight breakup caused by rudder flutter, which resulted from maintenance personnel failing to rebalance flight controls after repainting, leaving them overweight and unbalanced.
  • Flutter is a dangerous aerodynamic phenomenon that can cause catastrophic structural failure, often triggered by improperly balanced control surfaces, excessive speed, or structural flexibility, and is not easily detectable without precise engineering.
  • The article emphasizes the critical importance of accurately balancing flight control surfaces, and rebalancing them after any alterations like repainting, as deviations from manufacturer specifications can lead to deadly consequences.
  • A growing concern exists for high-performance homebuilt aircraft, as increased speeds coupled with builders potentially neglecting balance requirements or rigorous aerodynamic analysis can heighten the risk of flutter.
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The wreckage of a Grob G115D, a German-built, all-composite, aerobatic two-seat trainer, was spread out over an area nearly half a mile long and 400 feet wide-this despite the fact the airplane was sighted shortly before the accident by a witness on the ground who estimated its height, in level flight, as only 500 feet. The weather was good and was not considered a factor in the mishap.

Parts widely scattered along a line indicate an inflight breakup. The first items to separate from the airframe are at the beginning of the wreckage path; the fuselage and engine are usually found at the end. In this case, the first item in line was the top of the rudder. Various other pieces of empennage debris, including the stabilizer and both elevators, were found 900 feet from the main wreckage, as was a portion of the left wing and flap. Fragments of the acrylic canopy were scattered along the wreckage path, but although both pilots were wearing parachutes, there was no evidence of their having jettisoned the canopy. The lower portion of the rudder was never found.

Peter Garrison

Peter Garrison taught himself to use a slide rule and tin snips, built an airplane in his backyard, and flew it to Japan. He began contributing to FLYING in 1968, and he continues to share his columns, ""Technicalities"" and ""Aftermath,"" with FLYING readers.

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