What happened
On 28 September 2012, a Diamond DA 42 NG Twin Star, registration G-SELC, was conducting an instrument rating training flight at Staple andford Aerodrome, Essex. The flight involved a student pilot, an instructor, and an observer. Following several successful touch-and-go exercises on Runway 22L, the aircraft proceeded with a landing attempt.
During the final approach, the landing flaps were lowered, and the aircraft touched down on its main wheels just before the runway identification markings. The pilot maintained a nose-up attitude via the control column to allow the nosewheel to settle. Although the cockpit indicators initially showed the landing gear was down and locked, the nose landing gear collapsed approximately three seconds after touchdown. This collapse caused the propellers to strike the runway surface. The aircraft remained on the runway centerline and came to a stop without further incident. All three occupants exited the aircraft safely, and no injuries were reported.
The investigation
Following the event, the maintenance organisation conducted a thorough examination of the aircraft. The aircraft was placed on jacks, and technicians performed approximately 30 retraction and extension cycles. The investigation focused on the hydraulic actuators, the electro-hydraulic pump, and the gear warning systems. The inspection revealed that the gear retraction/extension mechanism and the associated warning systems were functioning correctly. Furthermore, the manual free-fall emergency mechanism was inspected and found to be in working order.
Findings
- The nose gear leg was found to have dropped freely into the downlock position.
- There was no evidence of mechanical failure within the retraction/extension system or the warning systems.
- Maintenance staff noted that if hydraulic pressure had been diverted from the downlock mechanism to the retraction system due to landing loads, visible damage to the system would have been present; however, no such damage was identified.