What happened
On 30 April 2015, a North American T-28A Trojan, registration N14113, was performing a takeoff run for a test flight following its annual maintenance at Duxford Airfield, Cambridgeshire. As the aircraft accelerated through 80 kt IAS, the pilot experienced intense lateral vibrations throughout the airframe. In response, the pilot immediately reduced throttle. Simultaneously, the nosewheel and yoke detached, causing the nose of the aircraft to drop. The propeller struck the runway surface, resulting in a shock-load to the engine and bent propeller blade tips. The aircraft traveled approximately 150 yards along the runway before coming to a halt, resting on the main landing gear and the remnants of the nose gear strut. There were no injuries to the pilot.
The investigation
The AAIB examined the nose landing gear (NLG) to determine the cause of the detachment. The investigation established that the failure originated at the top of the NLG forging. Specifically, a crack had developed, originating from a bolt hole used to secure the anti-shimme damper bracket. Further inspection of the component revealed that this crack had been propagating previously. However, these cracks were not identified during standard pre-flight or routine visual inspections, as no specific non-destructive testing (NDT) protocol existed for this particular part.
Findings
- The nose landing gear failed due to a crack propagating from a bolt hole in the anti-shimmy damper bracket.
- Evidence indicated the crack had been present and growing prior to the accident.
- Routine visual inspections were insufficient to detect the structural flaw.
Safety action
- The maintenance organisation responsible for the aircraft has implemented a new safety procedure to perform non-destructive testing (NDT) on the nose landing gear forging during future scheduled maintenance.