What happened
On July 23, 2022, a Diamond DA-20, registration EC-NFV, was performing takeoff and landing maneuvers at the La Axarquía aerodrome in Málaga, Spain. During the final takeoff attempt of the session, the nose wheel assembly detached while the aircraft was airborne.
Upon realizing the nose gear had separated, the crew notified ground services and remained airborne for approximately two hours. During this period, the crew reduced the aircraft's weight by burning off fuel and performed several low-altitude passes to test landing configurations. Ground personnel prepared the runway by applying foam to the landing surface to mitigate potential damage. At approximately 19:15 local time, the pilot executed an emergency landing at 55 knots. To protect the aircraft, the pilot maintained a high nose attitude for as long as possible, delaying nose contact with the runway until the final moments of the rollout. The aircraft sustained damage to the nose gear strut due to friction with the pavement, but the propeller and primary structure remained intact. The pilot and passenger were uninjured.
The investigation
The investigation focused on the structural failure of the nose gear assembly and the effectiveness of existing maintenance protocols. Investigators examined the remains of the nose gear strut and the pivot bolt found on the runway. A macrofractographic analysis of the fractured threaded end of the pivot bolt revealed that the failure originated in the thread valley due to high stress concentrations. The fracture progressed through the material via tension, ultimately resulting in a brittle or semi-brittle failure of the remaining material.
Investigators also reviewed the maintenance history, noting that a 200-hour inspection, which included a visual check of the pivot bolt threads, had been performed on the aircraft just one day prior to the accident. This inspection failed to detect the developing crack. Furthermore, the investigation noted that a similar incident involving a Diamond DA-20 occurred in 2018, which had led to a safety recommendation regarding maintenance intervals based on flight cycles, though the manufacturer had previously declined to implement changes to the current hour-based inspection regime.
Findings
- The primary cause of the accident was a service failure of the nose gear pivot bolt, characterized by a brittle fracture of the threaded end caused by an overload of stress.
- The fracture initiated in the thread valley, where high stress concentrations were present.
- Visual inspections performed during the 200-hour maintenance check were unable to detect the crack due to its location and the nature of the material failure.
- The aircraft's owner has since replaced the nose gear components across their fleet with a redesigned version that does not require liquid penetrant inspections.