What happened
On 24 May 2007, a Grob G115E Tutor, registration G-BYWE, was conducting a training flight at Colerne Airfield in Wiltshire. Following a successful landing, the pilot intended to perform a touch-and-go maneuver. However, as the nose of the aircraft touched the ground, a vibration and a distinct clunk were felt through the airframe. The pilot subsequently aborted the touch-and-go and slowed the aircraft to backtrack.
As the pilot applied right rudder to steer the aircraft, the nose landing gear collapsed. This impact caused the propeller to strike the runway, resulting in engine shock-loading and the engine stopping. There were no injuries to the two crew members on board, and the crew was able to exit the aircraft normally following the incident.
The investigation
Investigators examined the aircraft and determined that the nose leg sliding tube had been incorrectly reassembled during a recent maintenance period. Specifically, the sliding tube had not been secured to the flange. The attaching bolt had merely passed through the flange and the bottom fitting without properly securing the tube, allowing it to move freely.
This lack of security allowed the tube to migrate upwards, creating high bending loads on the lower end of the gas spring strut. This mechanical stress eventually caused the strut to fracture, leading to the structural failure of the nose leg. The investigation also looked into the maintenance history, noting that the aircraft had undergone a 50-hour inspection on 12 May 2007, during which the nosewheel bellows were replaced.
Findings
- The nose leg collapsed because the sliding tube was not secured to the flange during maintenance.
- The improper assembly allowed the tube to move upward, inducing bending loads that fractured the gas spring strut.
- Although the maintenance organization had implemented a duplicate inspection requirement for this critical task following previous similar incidents, this specific inspection was not performed on the leg assembly or sliding tube during the recent bellows replacement.