What happened
On 10 July 2012, a Piper PA34-200, registration ZS-ISD, was conducting a routine training flight near Port Alfred Aerodrome when the crew identified a mechanical issue. After approximately two hours of flight exercises in the General Flying Area, the instructor attempted to extend the undercarriage for landing. While the nose and right main gear indicated they were locked, the indicator for the left main landing gear failed to illuminate.
In an attempt to rectify the situation, the crew recycled the gear and utilized the emergency extension system, but the left gear remained in an unsafe condition. Despite an Air Traffic Control observation during a fly-past suggesting the gear appeared extended, the instructor declared an emergency. During the landing on Runway 2/28L, the aircraft initially touched down on the right main gear. However, upon contact with the runway, the left main landing gear collapsed. The aircraft veered left, traveling approximately 100 metres before exiting the runway onto the grass. The instructor and student sustained no injuries, though the aircraft suffered minor damage to the left wing underside and propeller blades.
The investigation
Following the incident, the aircraft was inspected by a maintenance organization to determine why the gear failed to lock. Investigators discovered that a bracket within the left main landing gear down-lock mechanism had fractured. This fracture prevented the necessary spring tension from holding the gear in the locked position. The investigation also noted that the failed bracket was an original part that had been in service for over 6,000 hours. Furthermore, records indicated the aircraft had been involved in a previous belly landing incident in October 2010, which may have introduced stress or damage to the component.
Findings
- The primary cause of the accident was an emergency landing necessitated by a mechanical failure of the landing gear.
- A fractured bracket in the undercarriage down-lock mechanism prevented the left main gear from securing in the down position.
- The failure was likely linked to a crack developing in the original part over time, potentially exacerbated by a previous landing incident involving a retracted gear state.