What happened
On July 17, 2005, at approximately 14:15, a BKSUT Evolution (registration F-PVIT) was participating in a demonstration flight involving eight Formula 1 aircraft at the Nevers aerodrome in Fourchambault, France. While flying the downwind leg of the circuit for runway 12, the pilot reported that debris was falling from the aircraft ahead. Simultaneously, witnesses observed the F-PVIT experiencing violent yawing motions.
In an attempt to avoid nearby residential buildings, the pilot executed a wide left turn. During this maneuver, the aircraft lost control, struck a public lighting pole, and crashed into the ground a few hundred meters southwest of the aerodrome. The pilot sustained serious injuries, and the aircraft was destroyed. The pilot reported that the aircraft was traveling at approximately 3/00 km/h and that there were no prior warning signs of the impending failure.
The investigation
The investigation focused on the structural integrity of the aircraft's tail section. Investigators recovered both halves of the composite vertical stabilizer, which had separated upstream of the aircraft's flight path.
Examination of the components revealed that the two halves of the stabilizer had been bonded at the leading edge of the horn boom using a layer of carbon fiber. However, this area had been sanded down too deeply. Furthermore, the investigation identified structural failures on the internal skin of the right stabilizer half, which were likely caused by aerodynamic bending stresses. These stresses were exacerbated by the loss of rigidity in the stabilizer spar, resulting from both the excessive sanding and the absence of a specific internal reinforcement.
Findings
- The structural failure was caused by the omission of a required internal reinforcement during the aircraft's construction.
- The structural integrity of the leading edge was further compromised by excessive sanding of the composite layers.
- The builder had identified a potential solution for the reinforcement during the assembly process but had continued with the construction without implementing the fix or suspending flight operations.