What happened
On 23 June 2002, a CFM Aircraft Ltd Streak Shadow SA-M, registration G-MGPH, was performing a private flight approximately 2.5 miles north of Spalding, Lincolnshire. While cruising at an altitude of roughly 2,000 feet, the engine RPM suddenly surged above the standard 6,000 RPM cruise setting. The pilot immediately reduced the throttle and transitioned into a glide descent, at which point the propeller became detached from the aircraft.
Upon inspection, the pilot confirmed that the flying controls remained functional and that the propeller had not struck the aircraft structure. The pilot selected a suitable field for an emergency landing, configured the flaps, and shut down the engine. During the landing, the aircraft touched down without incident, though the nosewheel subsequently struck a ditch, resulting in damage to the nosewheel assembly. There were no injuries to the pilot or the passenger.
The investigation
Investigators examined the threaded ends of the six propeller attachment bolts recovered from the gearbox flange. Metallurgical analysis revealed that the failure of the bolts was caused by bending fatigue. While the bolt material met the necessary strength standards, the ends of the bolts showed signs of being sawn rather than being standard roll-thread fasteners, and significant corrosion was present. One bolt end was notably longer than the others and exhibited corrosion on the fracture face, suggesting it may have been the initial point of failure.
Prior to this event, the aircraft had experienced a similar propeller loss in July 2001. Following that incident, a new installation method was used on G-MGPH involving hexagon-head steel bolts. This method was intended to ensure the propeller was properly seated on the gearbox flange. However, the aircraft had only flown 8.5 hours with this specific configuration before the propeller detached again.