What happened
On 15 September 2019, a Skyranger Swift 912S, registration G-SKSW, was performing a private flight from Clacton airfield to High Cross airstrip in Hertfordshire. The weather conditions were fine, and the approach to Runway 22 was completed without incident. The aircraft made a normal touchdown on its main landing gear.
As the aircraft continued its landing roll and the nose was lowered, the nose landing gear fork failed. This caused the nosewheel to dig into the firm grass surface, resulting in a sudden deceleration and causing the aircraft to pitch forward. The aircraft eventually came to rest in an inverted position. The pilot and one passenger, both wearing four-point harnesses, were uninjured and were able to exit the aircraft without assistance.
The investigation
The AAIB examined the wreckage and found significant damage to the engine, propeller, cowling, cockpit windscreen, and both wings. The nose landing gear assembly showed that the left leg of the fork had failed at the welded joint where it meets the down tube. The right leg of the fork remained attached to the down tube but had folded rearwards.
A metallurgical examination of the fractured component was conducted. The analysis determined that the failure occurred due to ductile overload, meaning the metal was subjected to forces exceeding its design strength. The examination found no evidence of material defects, porosity, or pre-existing progressive cracking within the weld beads themselves. While some light corrosion was present on the fracture surface, there was no indication of a long-standing crack growth pattern.
Findings
- The nose landing gear left fork failed because it was subjected to loads beyond its structural capacity.
- It is probable that the gear fork had been weakened by damage sustained during a recent, though unidentified, taxiing or landing event.
- The design of the Skyranger Swift 912S, specifically the nosewheel fairing, likely prevented the pilot from detecting any structural damage during the pre-flight inspection.