What happened
On 26 July 2015, a Tecnam P2002-JF, registration F-HFCM, was conducting a dual-command training flight at Compiègne aerodrome. The flight, involving a student pilot and an instructor, was intended to practice landing in crosswind conditions. Following a series of circuits and a final touch-and-go, the aircraft returned to land on an unpaved runway. While taxiing along the runway, the left main landing gear failed, resulting in severe damage to the aircraft. No injuries were reported.
The investigation
The BEA examined the wreckage and the components of the main landing gear assemblies. The investigation focused on the central attachment bolt of the left main landing gear, which had broken into two pieces. Laboratory analysis using scanning electron microscopy (SEM) was performed on both the left and right landing gear attachment bolts. Investigators also reviewed the aircraft's maintenance history, including previous landing gear replacements following a hard landing in 2014, and examined the condition of the metal flanges and leather spacers used as shock absorbers.
Findings
Technical examination revealed that the central attachment bolt of the left main landing gear had suffered a fatigue fracture. The fracture surface showed evidence of multiple initiation sites, a pattern characteristic of alternate bending loading. Notably, the right main landing gear bolt also exhibited a fatigue crack in the same location.
Investigators determined that the failure was caused by a loss of tightness in the assembly. Under normal operating loads, the leather spacer at the interface between the fuselage frame and the leaf spring compresses, which can create play in the assembly. This play subjected the bolts to cyclic bending stresses rather than pure tension. The presence of rotational friction marks on the bolts and the deformation of the metal flanges and leather spacers confirmed that the assembly had been subjected to abnormally high cyclic loads. At the time of the accident, the maintenance program only required torque checks every 100 hours, and there was no requirement to disassemble the gear to inspect for such fatigue damage.