History of Flight
The aircraft, a Gill SA Pulsar registered G-BSFA, was taking off from Staverton (Gloucestershire Aerodrome) for a local flight when the nosewheel detached during rotation. The occupants were unaware of the separation until informed by radio from a following aircraft. They circled the airfield for 20 minutes while emergency services assembled, then performed a low approach and go-around. Observers confirmed the nosewheel and fairing were missing. On the subsequent landing, the pilot held the nose off as long as possible without wheel braking. The nose leg settled onto the runway, slid for about 30 metres, then dug in, bringing the aircraft to an abrupt halt. Both occupants were uninjured and exited normally.
Description of the Nose Landing Gear
The nose landing gear strut consists of a thick-walled tube with a castoring nosewheel assembly at the lower end. The upper end is welded to a cross tube beneath the firewall. Lateral bracing is provided by additional tubes, and a drag brace runs from the strut to the engine mount. Some aircraft, including G-BSFA, have a damper incorporated. The detached nosewheel assembly was recovered and sent for examination.
Examination of the Nose Leg
Metallurgical examination of the nose leg components revealed that the nosewheel pivot pin had suffered a fatigue fracture approximately in line with the upper face of the collar. The failure resulted from reverse bending in the fore-and-aft direction, with multiple initiation sites. Secondary fatigue sites indicated loads when the nosewheel was not straight. An intact strut removed previously due to a bent pin also showed fatigue cracks: one (crack 'A') similar to the failed pin's fracture plane, and another (crack 'B') from forward bending fatigue followed by overload. A discontinuity at 'C' was a weld fusion lack, likely uninfluential. The steel tensile strength and weld quality were not considered contributory.
Other Information
The Popular Flying Association (PFA) oversees airworthiness for this type. The aircraft had accumulated over 300 flying hours, high relative to others on the UK register. The PFA knew of no similar failures. The aircraft was previously operated from a grass airfield but currently based at Staverton with paved surfaces.
Discussion
The pilot appreciated the other aircraft's warning; without it, precautions might not have been taken. The failure was fatigue-related, not a single event. The intact strut corroborated fatigue damage predating an overload. Since the aircraft operated typically, failure likely resulted from normal in-service loads, raising questions about design suitability for non-smooth surfaces and whether a safe life should be imposed. The design hindered reliable crack inspection. The owner replaced the nose gear with a different design from the kit manufacturer, already in US use, now being evaluated by the PFA.