What happened
On 13 June 2009, a private flight departing from Northrepps Airstrip, near Cromer, Norfolk, was interrupted by sudden mechanical issues. Approximately 15 minutes after takeoff, while flying at an altitude below 600 feet, the pilot of the X’Air 582, registration G-BZAF, experienced a violent vibration throughout the airframe. This was immediately followed by a perceived loss of lift from the right wing.
Following the vibration, the pilot transmitted a MAYDAY call and executed a forced landing into a field of standing crops near Carland Cross, Cornwall. Upon touchdown, the aircraft's nosewheel struck a rut, causing the aircraft to nose over and come to rest inverted. The pilot was uninjured in the 0 fatalities accident, though the aircraft was damaged beyond economic repair.
The investigation
Investigators examined the wreckage and digital photographs taken at the accident site. While the aircraft was inverted, one propeller blade was found projecting vertically downwards and appeared undamaged. However, the blade projecting vertically upwards showed damage to the leading edge near the hub end.
An engineering examination of the propeller blades revealed that one blade had been separated into two pieces by a saw-like fracture. This blade showed evidence of a partial bending failure at the hub end. Detailed cross-sectional analysis of the blades identified areas where the resin within the surface plies had cracked, leading to local fractures of the carbon fibres. The examination also revealed poorly impregnated glass fibres near the root end, which showed evidence of crack growth.
Findings
- The pilot had previously flown through rain for approximately 35 minutes during a prior flight and did not use covers for the propellers while the aircraft was parked.
- A partial bending failure of a propeller blade likely generated the intense vibrations experienced by the pilot.
- It is possible that latent disbonding and aerodynamic forces during flight caused the propeller to crack, though the exact timing of this failure could not be determined.
- The presence of protruding wing battens noted after the accident was likely caused by the weight of the aircraft while it was inverted on the ground rather than an in-flight failure.