What happened
On 22 June 2006, a Fuji FA-200-160, registration G-FEWG, was conducting a private flight from Turweston to Temple Bruer. While cruising at 1,900 ft near Grantham, the aircraft suddenly experienced intense vibrations. The pilot, fearing a total engine failure, reduced the throttle and mixture and declared a MAYDAY.
During the descent, the pilot attempted to navigate toward the airfield at RAF Cranwell. Despite switching off the magnetos to stop the engine, the propeller continued to windmill, and the violent shaking persisted. The pilot eventually identified the runway at Barkstone Heath and performed a downwind gliding approach. The aircraft landed safely on the runway, though the pilot refrained from using brakes due to uncertainty regarding potential structural damage from the vibration. No injuries were sustained by the pilot.
The investigation
Post-flight inspections of the Fuji FA-200-160 revealed that the outer six inches of one propeller blade tip were missing. While the aircraft otherwise appeared largely undamaged, investigators noted that two exhaust pipes were loose at their manifold attachments.
Detailed metallographic analysis of the propeller was conducted at a specialist laboratory. Using optical and scanning electron microscopy, investigators determined that a fatigue crack had developed near the leading edge. This crack had spread across roughly two-thirds of the blade's chord before the remaining material failed due to overload. High-magnification examination of the crack's origin revealed a tiny, flattened area with shallow scrape marks, suggesting a very small impact or bruise on the leading edge had acted as the starting point for the fracture.
Findings
- The propeller failure was caused by a fatigue crack originating near the leading edge of the blade.
- The crack propagated across two-thirds of the blade chord before the tip broke away.
- The failure was preceded by a period of time where the crack was actively growing, well beyond the duration of the final flight.
- A very small, seemingly insignificant bruise on the leading edge likely served as the stress concentrator that initiated the fatigue.