What happened
On May 29, 2013, a Piper PA-34 Seneca, registration EI-CMT, was conducting a dual flight training mission when it experienced a nose landing gear collapse at Cork Airport. The aircraft, operated for instructional purposes, had completed a series of training maneuvers, including a low approach at Shannon Airport and various air work exercises, before returning to Cork.
During the landing on runway 35, the flight crew noted a normal approach with all gear indications showing green. However, as the aircraft entered the landing roll, the nose landing gear suddenly retracted into the wheel well. This caused the aircraft's nose and both propellers to strike the runway surface, resulting in substantial damage to the airframe. There were no injuries to the instructor or the student on board.
The investigation
Investigators from the AAIU examined the aircraft's nose landing gear (NLG) actuation mechanism to determine why the gear failed to remain locked. The investigation focused on the over-centre, geometric lock that relies on the stability of the upper and lower drag links.
Upon inspection, the team found that the geometric lock condition was not being maintained. Specifically, the investigation identified two critical mechanical failures: the down lock link bolt had failed in bending, and the pin holes within the down lock link barrel had undergone elongation. This deformation compromised the spring-loaded mechanism, preventing the link from maintaining the necessary length to secure the gear in the down position.
Review of the aircraft's maintenance logs showed that all required inspections and servicing had been performed correctly, with no recent history of heavy landings or gear-related defects recorded.
Findings
- The nose landing gear retracted during the landing roll due to a failure in the locking mechanism.
- The bending failure of the down lock link bolt and the elongation of the pin holes prevented the maintenance of the over-centre geometric lock.
- The Piper PA-34 Seneca type has a documented history of similar nose landing gear collapses, a complex issue that the manufacturer and the FAA have previously struggled to isolate to a single root cause.