What happened
On 30 December 1997, a Europa aircraft, registration G-BWYD, was conducting a private training flight at Kemble Airfield in Gloucestershire. The flight involved an instructor providing re-familiarisation training to a co-owner. During the first circuit, the pilot selected the landing gear to the down position, and the instructor confirmed the selection by observing the green indication light and checking the safety latch on the selector lever.
While performing a landing on a grass runway, the aircraft experienced a skip due to an undulation in the surface. During the landing roll, the instructor noticed the right wing dropping. A loud noise occurred in the cockpit, and the aircraft sank onto its underside. During the subsequent ground slide, one propeller blade sheared off at the hub. Following the incident, the aircraft was lifted by a crane and the gear was lowered. However, while being manoeuvred on the tarmac toward a hangar, the landing gear collapsed a second time, even though the selector lever remained in the down position.
The investigation
The investigation examined the landing gear mechanism, which includes a retractable mainwheel, a tailwheel, and two outrigger wheels. The mechanism uses an over-centre design, and a safety latch is intended to prevent accidental retraction. Investigators found that the landing gear selector lever had suffered distortion and that two of its attachment bolt holes had been elongated by approximately 1.5 mm.
Evidence of file marks within these holes suggested that the holes had been manually enlarged at an earlier date, likely to facilitate the assembly of the lever. This resulted in a poor-quality joint that relied on friction rather than a secure fit. This slackness allowed for additional movement within the mechanism when the aircraft encountered ground undulations.
Findings
- The primary cause of the initial collapse was the mechanical play in the landing gear linkage caused by elongated bolt holes.
- The presence of file marks indicates the lever had been previously modified to fit the mechanism, creating a loose joint.
- This excessive free play allowed the gear mechanism to move away from its over-centre stop when encountering bumps on the grass runway.
- The second collapse on the tarmac may have been caused by the weight of the occupant inducing further distortion of the selector lever, which was being held in place only by the safety latch.