What happened
On 3 November 2005, a Grob G115E, registration G-BYVZ, was conducting a training flight at RAF Church Fenton, North Yorkshire. The pilot had completed several 25-minute sorties in the aircraft earlier that day. During the fourth flight, the pilot performed a standard powered approach to Runway 16. Following a smooth touchdown on the main wheels, the nose wheel was lowered onto the runway to begin the landing roll. However, as the aircraft began to decelerate, the nose wheel assembly suddenly collapsed. The aircraft subsequently skidded along the runway until it came to a complete stop. There were no injuries to the pilot or the passenger on board, though the aircraft sustained damage to the nose wheel assembly and the propeller.
The investigation
The investigation focused on the mechanical integrity of the nose landing gear. The assembly is composed of a tubular strut, a sliding tube, and a gas spring strut. The top of the sliding tube is held within the strut, while the bottom of the sliding tube and the gas spring strut are secured to a flange by a specific bolt.
An engineering review by the operator's maintenance organization determined that the nose landing gear had undergone assembly during a 150-hour maintenance interval. The investigation established that the bolt used during this maintenance had been incorrectly installed, such that it only secured the bottom fitting of the gas spring strut to the flange, rather than passing through both the sliding tube and the bottom fitting. This error left the assembly vulnerable to the forces applied during landing.
Findings
- The nose landing gear was improperly assembled during a recent 150-hour maintenance period.
- The bolt intended to secure the sliding tube and gas spring strut to the flange failed to pass through the sliding tube, leaving the assembly unstable.
- The weight applied to the nose wheel during the landing sequence caused the bottom of the gas spring strut to fail, leading to the collapse of the nose leg.