What happened
On 20 August 2011, an Acrosport 2, registration G-CGAK, was performing a private flight at Duxford Airfield, Cambridgeshire. The pilot, a flight instructor, executed what was perceived as a normal landing into the wind. However, during the subsequent ground roll, the right landing gear collapsed. The impact caused damage to the propeller, the wing, and the right landing gear, and resulted in a shock-load to the engine. There were no injuries to the pilot or the passenger on board.
The investigation
Investigators examined the design and condition of the aircraft's fixed main landing gear, which utilizes a suspension unit within the cross-strut. The investigation focused on the right cross-strut, where Bolt ‘A’ had been partially pulled out of the inner tube, leaving a weakened section of metal. This damage was consistent with the strut bottoming out during a heavy landing.
Evidence was considered regarding a previous incident in March 2011, where the same aircraft had landed heavily on its right main wheel. While the aircraft had flown approximately 15 hours and 20 landings since that event, the investigation looked into whether that impact had initiated the structural degradation. The investigation also considered whether the welds on a previously installed insert within the inner tube might have failed, or if there were manufacturing defects in the tube's formation.
Findings
- The collapse was caused by the failure of the right landing gear cross-strut due to a weakened inner tube.
- The damage to the inner tube was consistent with a heavy landing that occurred months prior to the accident.
- It is possible that the structural integrity of the inner tube was compromised during the March 2011 landing, and subsequent landings caused the bolt to gradually pull through the metal.
- The investigation could not definitively confirm if the failure was due to improper welding of an insert or a defect in the tube's manufacturing, as the damage could not be fully assessed without disassembly.