What happened
On 28 June 2008, a Morane Saulnier Rallye 180T, registration G-BTOW, was completing its ninth glider tow of the day at Gransden Lodge Airfield, Cambridgeshire. The pilot reported that the initial portion of the landing was normal. However, as the aircraft reached the end of the landing run while taxiing at a low speed, the nose gear collapsed. The nose gear leg folded back underneath the fuselage, causing the propeller to strike the ground. The aircraft came to a halt resting on the lower section of the engine cowling. The pilot, who was wearing a full harness, sustained no injuries and was able to exit the aircraft via the standard exit.
The investigation
The AAIB investigation focused on the structural failure of the nose landing gear oleo. Investigators discovered that the fitting at the top of the nose gear oleo had failed, which allowed the gear to rotate backwards. This fitting was found on the grass approximately 10 feet away from the aircraft. Upon examination of the fitting, it was noted that both attachment lugs had failed in nearly identical positions across their 7 mm thick sections. The investigation also reviewed the aircraft's usage history, noting that the operator had flown the aircraft for approximately 150 hours per year since 1992, with a landing rate of roughly five per hour, totaling over 11,000 landings at the time of the accident.
Findings
- The failure was caused by the growth of fatigue cracks originating from the bore of the attachment lugs.
- Both fractures showed pre-existing cracks that had extended into the lug to depths of 3 mm and 1.5 mm.
- The final failure of the attachment lugs occurred due to an overload following the fatigue-related weakening of the metal.