What happened
On 10 February 2003, a Grob G115D 2, registration G-BVHG, was conducting a training flight at Plymouth City Airport in Devon. The aircraft had successfully completed four dual circuits with an instructor and a student. Following a running change where a new student boarded while the engine remained running, the aircraft began its taxi for takeoff. During the taxi sequence, the aircraft performed a sharp 110-degree left turn to backtrack along Runway 13. During this manoeuvre, the nose landing gear collapsed. The impact caused the propeller to strike the ground and resulted in a shock-load to the engine. The two crew members on board were uninjured and exited the aircraft safely.
The investigation
Investigators examined the aircraft after it was recovered to a hangar. The initial inspection identified that the upper torque link had failed, leading to the collapse of the nose leg. Further technical analysis revealed that the failure of the torque link and several other components was caused by the incorrect assembly of the nose landing gear.
The nose leg assembly consists of an outer tube, a sliding tube connected to the nosewheel fork, and a gas spring strut. The investigation established that a specific bolt intended to secure a 'T' fitting to the housing had failed to secure the lower end of the sliding tube. This allowed the sliding tube to migrate upwards out of its housing, which subsequently induced bending loads into the gas spring strut, leading to the structural failure of the strut and the torque link.