What happened
On May 24, 2003, a Beech 23 Musketeer, registration I-MIFA, was performing a recreational flight that concluded with an approach to Brescia Montichiari Airport. The flight, which had previously included a stop at Caiolo, was being operated by a pilot sitting in the left seat, with a passenger sitting in the right seat.
Upon landing on runway 32 at 11:43 UTC, the aircraft experienced a significant failure of the right landing gear. During the subsequent deceleration phase on the runway, the aircraft began to deviate sharply to the right and the right wing dipped. The aircraft eventually came to a halt approximately 100 meters from the runway edge. There were no injuries to the two occupants, though the aircraft sustained damage to the right gear strut and caused minor abrasions to the runway surface.
The investigation
The ANSV examined the mechanical condition of the landing gear and the structural components of the shock absorber. The investigation focused on the internal mechanism of the strut, which utilizes eight rubber discs held by a central guide rod and a compression plate secured by a 5mm diameter split pin.
Physical evidence showed that the right gear fork and wheel had rotated approximately 180 degrees forward from their original position. Detailed inspection of the shock absorber revealed a slight deformation on the threaded end of the guide rod and an arc-shaped deformation on the bolt securing the gear leg to the wing structure. Crucially, the split pin connecting the compression plate to the guide rod had fractured. Microscopic analysis of the fracture surface showed a crystalline appearance with "fish-eye" propagation striations and no evidence of fatigue or corrosion, indicating a dynamic overload failure occurring in three distinct stages.
Findings
- The primary cause of the accident was an excessive vertical landing rate (a heavy landing).
- The investigation determined that the landing gear had likely undergone at least two prior abnormal stresses, which initiated the progressive failure of the split pin.
- During the final landing, the high vertical impact caused excessive compression of the rubber discs, forcing the guide rod to strike the mounting bolt. This impact created intense shear stress on the split pin, leading to its final rupture.
- The failure of the pin caused the compression plate to detach from the guide rod, allowing the wheel and fork assembly to swing forward and lose structural alignment.
- The investigation noted that the landing was performed by the passenger, who was seated in the non-standard right-hand seat, under conditions involving a slight tailwind, which likely led to the misjudgment of flight parameters.