What happened
On 30 June 2017, a Piper PA-23-250 Aztec, registration G-BCCE, was conducting a private flight at Shoreham Airport, Sussex. Following a training session that included several landings and a simulated single-engine go-around, the pilot attempted to land the aircraft. Upon selecting the landing gear to the down position, the cockpit indicators signaled that the nose gear had failed to lock.
After consulting with Air Traffic Control, which confirmed the gear was not fully extended, the pilot exited the landing circuit to attempt to troubleshoot the issue using the aircraft's checklists. When the malfunction could not be rectified, the pilot proceeded to land the aircraft on the grass runway. The impact caused damage to the nose landing gear and the forward fuselage, but there were no injuries to the two occupants on board.
The investigation
Investigators examined the aircraft once it had been moved to a maintenance facility. The inspection focused on the nose landing gear assembly, specifically the drag links and attachment points. The investigation revealed that the upper drag link attachment bolt had fractured. Analysis of the fracture surfaces indicated that the failure was caused by reverse bending fatigue, with evidence of corrosion and contamination suggesting the fatigue crack had been developing for a significant period.
Furthermore, the examination found that the upper drag link attachment lugs were distorted, and the two inboard lugs had developed cracks. Similar to the bolt, the presence of dirt within these cracks indicated that these structural issues had been present for some time prior to the accident.
Findings
- The nose landing gear failed to reach the locked position because the upper drag link had detached from the aircraft structure.
- The primary cause of the failure was reverse bending fatigue of the upper drag link attachment bolt.
- The failure of the inboard attachment lugs likely caused the drag link to flex, creating the excessive cyclic loading that led to the bolt's failure.