What happened
On the night of 12 November 2002, a Piper PA34-200T Seneca II, registration ZK-FMW, was completing a charter flight involving stops at Palmerston North and Napier. The aircraft was returning to Ardmore Aerodrome carrying a pilot and three passengers. During the landing on a lighted runway, the aircraft's undercarriage began to fail.
After the nose wheel made contact with the runway, the undercarriage collapsed, causing the aircraft to scrape along the pavement for approximately 100 meters. The aircraft then veered off the runway onto the grass. While the aircraft sustained substantial damage—including broken propellers and a ruptured fuel tank—all four occupants were able to exit the aircraft unassisted and escaped without injury.
The investigation
Investigators examined the wreckage and the aircraft's maintenance history, finding that the plane had been maintained to a high standard and was in excellent condition. The investigation focused on why the gear failed despite the pilot and a passenger both observing the three green lights indicating the gear was down and locked.
Technical testing of the undercarriage rigging showed that the components were within operational limits. However, a small amount of play was noted in the drag brace, which allowed the nose wheel to move slightly forward and backward. Investigators also looked into the possibility of an electrical fault or the pilot accidentally moving the gear selector, but no definitive evidence of such errors was found.
Findings
- The pilot was appropriately qualified and fit for duty.
- The aircraft ZK-FMW was well-maintained and in good condition.
- The specific cause of the undercarriage collapse could not be conclusively established.
- A possible, though unconfirmed, trigger was a combination of landing forces and the existing play in the undercarriage drag brace that allowed the nose gear to move past its over-centre position, releasing the downlock.