What happened
On January 21, 1996, a Robin DR 300/140, registration F-BSLU, was performing a local VFR flight with one pilot and two passengers at the Bordeaux-Léognan-Saucats airfield. Following a normal landing on runway 04, the aircraft began taxiing. During this phase, the nose gear suddenly collapsed underneath the engine.
The aircraft slid approximately 100 meters along the runway before veering off to the left and coming to a halt. During the excursion, the nose of the aircraft made contact with the runway surface. Following the stop, the pilot evacuated the passengers and discovered the onset of a fire near the engine. The fire was quickly extinguished by a bystander using a portable fire extinguisher.
The investigation
The investigation focused on the structural failure of the nose gear, which was a S.A.B. T2 type. Physical and microscopic examinations revealed that the failure originated from two fatigue cracks located on either side of the upper attachment plate. These cracks were situated in a heat-affected zone created during the welding process that joins the plate to the gear strut.
Investigators also examined the maintenance history and existing airworthiness directives. While previous directives required inspections of the lower plate and certain weld areas, the upper attachment plate was located behind the engine and was not accessible without significant maintenance disassembly. Consequently, there was no requirement for regular inspections of this specific component.
Findings
- The nose gear failure was caused by undetected fatigue cracks on the upper attachment plate.
- The cracks developed in a thermally affected zone where the material structure had been altered by welding.
- Current maintenance and inspection procedures did not include the upper attachment plate, making it impossible to detect the cracks during routine checks.
- The aircraft was within weight and balance limits, and the pilot was properly licensed and qualified.
- Similar failures had been observed in previous accidents involving other Robin aircraft, such as F-BRZE and F-BTBM.