What happened
On 16 February 2006, a Socata TB10, registration G-BNRA, was operating at Nottingham Airport (Tollerton) when a significant mechanical failure occurred. During the flight, a propeller blade released from its hub due to fatigue cracking. This failure caused a propeller imbalance, which subsequently led to the engine partially separating from the aircraft airframe.
The investigation
The AAIB examined the failed components and reviewed the accident report submitted by the pilot. The investigation focused on the structural integrity of the propeller hub and the manufacturing history of the components. Investigators analyzed the nature of the fatigue cracking present in the hub material.
Findings
- The primary cause of the incident was the fatigue failure of a blade in the propeller hub.
- The investigation established that the fatigue cracking was partially caused by non-optimal temperature conditions during the forging process of the hub material.
- While a Service Bulletin existed to address this specific hazard, the lack of a mandatory Airworthiness Directive at the time meant that the necessary inspections or part replacements had not been implemented on G-BNRA prior to the accident.