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Bad Vibrations

Gemini Sparkle

Key Takeaways:

  • The inflight breakup of a Grob G115D was attributed to rudder flutter, which resulted from maintenance personnel failing to rebalance the flight controls after repainting, leaving them overweight and tail-heavy beyond manufacturer specifications.
  • Flutter is a destructive aeroelastic phenomenon that can cause aircraft disintegration, primarily triggered by high speeds or, more commonly, by improperly balanced flight control surfaces due to maintenance oversights or design choices (e.g., omitting balance weights).
  • The increasing speed capabilities of modern homebuilt aircraft present a heightened flutter risk, emphasizing the critical importance for builders to ensure rigorous control surface balancing and structural integrity, as these factors are complex and often underestimated.
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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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