What happened
On 6 August 2009, a Pegasus Quantum 15, registration G-MZIU, was conducting a private flight from Rufforth Airfield to Crosland Moor Airfield. While climbing through approximately 1,800 ft amsl, the aircraft experienced a sudden, violent event characterized by loud banging and intense shaking. This was caused by the detachment of one blade from the three-bladed propeller at its root.
The resulting imbalance triggered a severe vibration that caused the aircraft to roll into a spiral dive of more than 60 degrees. During this descent, the engine failed, and the pilot received terrain warnings from GPS equipment indicating the aircraft had dropped below 500 ft agl. The pilot managed to arrest the spiral and slow the aircraft to its minimum sink rate.
With limited options, the pilot performed a forced landing on a steep, 15-degree upslope field near Lepton. While the landing was successful, the pilot sustained serious spinal injuries, including fractured neck vertebrae, caused by an impact with the aircraft's 'A' frame during the initial loss of control. The aircraft sustained significant damage, including the loss of carburettors and engine mounts, and was subsequently declared beyond economic repair.
The investigation
The AAIB examined the aircraft and the detached propeller component. The propeller featured a glass and carbon fibre reinforced outer skin with a foam core. Although a specialist examination of the remaining piece in the hub did not reveal an obvious cause for the failure, there were indications of a pre-existing crack in the fracture region.
Investigators also noted that the aircraft may have been involved in a previous minor accident, though it was unconfirmed if the propeller had been replaced following that event. The investigation also considered a previous incident involving a different aircraft type with similar composite blade delamination, though no widespread safety issue with such propellers was identified.