Overview
On 30 November 2004 at 1345 UTC, a Piper PA-30 Twin Comanche, registration G-AVPS, experienced a landing gear collapse during landing at Farley Farm Airstrip in Romsey, Hampshire. The aircraft was on a private flight from Gloucester Airport for its annual inspection. The pilot, the sole occupant, was uninjured.
History of the Flight
The pilot flew over the airstrip to assess conditions before lowering the landing gear and beginning an approach. After a go-around from the first approach due to being too high, the pilot landed on the second approach. The aircraft touched down on wet grass approximately 250 metres from the threshold of Runway 04. The landing appeared normal, but when brakes were applied, the landing gear collapsed. The aircraft came to rest level, and the pilot vacated unaided.
Landing Gear System
The Piper PA-30 Twin Comanche uses a single electric motor driving a screw jack to operate the landing gear. The screw jack moves two Bowden cables for the main gear and a push rod for the nose gear. Limit switches shut off the motor and illuminate a green 'down locked' light when the gear is fully extended. However, if the nose gear drag link does not lock over centre, the limit switch can close prematurely, causing the green light to illuminate even if the gear is not secure. In such cases, rearward forces on the nose gear during landing can cause the drag link to fold, transmitting forces to the motor mount, which is not designed for landing loads. This can lead to motor detachment and main gear retraction.
Aircraft History
The pilot reported difficulties lowering the landing gear after the previous annual inspection. On one flight, the green light did not illuminate despite normal gear operation. On another, the nose gear only partially extended, but the pilot manually extended and locked it. Similar issues have been reported by other Twin Comanche and single-engine Comanche operators, often attributed to friction, misalignment, poor maintenance, or foreign matter.
Conclusion
Investigation determined that the damage to the retraction mechanism was consistent with the nose gear leg not being locked down prior to touchdown. During the landing roll, the nose gear folded rearward, overloading the motor attachments. The motor was pulled from its mounting, causing the main gear cables to retract and leading to total landing gear collapse.