What happened
On 7 December 2020, a Grob G115A, registration G-GPSX, was conducting a training flight at Nottingham City Airport when the nose landing gear failed. During a series of touch-and-go landings, the crew heard a cracking noise during one circuit. While the subsequent landing appeared normal, a much louder cracking sound was heard during the following attempt as the student pilot applied full power for takeoff.
Following reports from another aircraft in the circuit that the nosewheel appeared to be swaying, the instructor took control and declared a MAYDAY. To mitigate the impact, the instructor extended the flare to minimize the duration the nose gear was in contact with the runway. During the landing rollout, the aircraft transitioned onto the upper portion of the nose gear. The assembly dragged behind the aircraft, remaining attached only by the scissor torque link, which caused the propeller blades to strike the ground.
There were no injuries to the two crew members on board, though the aircraft sustained a collapsed nosewheel and a bent propeller.
The investigation
The AAIB examined the nose landing gear assembly, which utilizes a gas spring strut shock absorber. The investigation focused on the failure of the piston rod, which fractured at the start of its threaded section. Investigators also looked into the history of the sliding tube, a component designed to protect the gas spring strut from bending loads.
While the sliding tube was found to have fallen from the aircraft, no fragments of the tube were recovered from the flange. The investigation also reviewed the maintenance history of G-GPSX, noting that the nose landing gear had not been dismantled for maintenance since August 2011, having accumulated approximately 1,000 flight hours since that time.
Findings
- The failure of the nose landing gear gas strut piston rod was caused by overload.
- Although previous similar failures on the Grob G115 were linked to the incorrect installation of the sliding tube during maintenance, this was not the case here, as the aircraft had flown 1,000 hours since its last gear maintenance.
- It could not be determined exactly how the sliding tube failed or why no fragments were found in the flange.