What happened
On 28 October 2002, a DH88 Comet, registration G-ACSS, was conducting a local test flight at Old Warden Aerodrome, Bedfordshire, to obtain a Permit to Fly. The flight was a private operation with a single pilot on board. During the landing phase on Runway 29, the aircraft experienced a series of bounces. The pilot attempted to dampen these bounces by lowering the nose, but the aircraft bounced four times. Upon the fifth touchdown, the right main landing gear collapsed. The aircraft subsequently slid in a tightening arc, with the right wingtip and engine nacelle making contact with the ground, before coming to rest.
The investigation
The investigation examined the aircraft's landing gear components and reviewed photographic evidence of the landing sequence. The inspection of the grass runway showed no significant depressions, though the surface was slightly uneven. Analysis of wheel marks indicated that each successive bounce involved a firmer contact with the ground.
Physical examination of the failed right landing gear revealed that the lower drag brace had bent at the cross-tie, and the upper drag brace struts had buckled. Crucially, the rivets connecting the screwjack nut to the ram had failed in shear due to tensile forces. The investigation also found that the movement of the freed ram pushed the jack body into the wing, puncturing the engine oil tank.
Findings
- The aircraft's fifth touchdown occurred on the right main wheel slightly before the left wheel.
- At this moment, the right spring strut reached its limit of compression.
- The full compression of the spring strut generated high wheel drag loads.
- These loads caused the upper drag brace struts to become unstable and bow.
- The resulting geometry created significant tensile forces within the screwjack assembly, which were sufficient to shear the attachment rivets.
- The collapse resulted in no injuries to the pilot, but caused severe damage to the right landing gear, the right engine nacelle, and the right wingtip.