What happened
On May 1, 2005, a Socata Gardan GY 80-180, registration F-BNQX, was conducting a cross-country flight from Châtellerault to Toulouse Lasbordes. The aircraft was carrying a pilot and two passengers. As the aircraft approached the AE entry point, approximately ten nautical miles from the runway, the pilot noticed intense vibrations. Unable to identify the source of the shaking, the pilot notified air traffic control and climbed from 2,000 to 3,000 feet to prepare for a potential forced landing in a field.
Upon deciding to land on runway 16, the pilot executed a 360-degree turn during the base leg while reducing engine power to manage the descent. During the final approach, the vibrations became increasingly severe. To mitigate the situation, the pilot shut down the engine by leaning the mixture and successfully completed the landing without further incident. There were no fatalities or injuries among the three occupants.
The investigation
Post-flight inspection of the Sensenich propeller revealed that a 13-centimeter section had broken off from the tip of one blade. Investigators examined the fracture surface and identified a deep cavity on the underside of the blade, near the leading edge, measuring 2 mm in depth and 4 mm in length. This feature was caused by a prior impact with a metallic object while the propeller was stationary. The investigation established that this damage was not detected during the pre-flight inspection.
Findings
- The propeller blade failure was caused by fatigue cracking originating from a pre-existing impact site.
- The fracture surface exhibited three distinct zones: an initiation zone (the impact cavity), a smooth 75 mm zone of fatigue crack propagation, and a rough 45-degree zone characteristic of an overload failure.
- The loss of the blade tip created a significant imbalance, leading to the intense vibrations experienced by the pilot.