What happened
On 27 July 2008, a Shorts SC.7 Skyvan, registration G-BEOL, was conducting a private flight from Manston toward Weston-on-the-Green. During the final stages of the approach to Weston-on-the-Green, the aircraft experienced a rapid increase in the rate of sink. This resulted in a heavy landing on the runway.
Following the impact, the aircraft veered sharply to the right. Fearing significant structural damage, the pilot performed a flyby inspection at Weston-on-the-Green, which confirmed that the right main landing gear had sustained severe damage and had folded aft. The pilot subsequently diverted to Oxford Airport and declared an emergency. The aircraft landed on the 900-metre grass Runway 21. Despite the collapse of the right gear, the pilot maintained directional control, and there were no injuries and no fire.
The investigation
Investigators examined the wreckage of the right main landing gear and discovered that the shock absorber had disconnected from the lower trunnion. The retaining nut, which is intended to secure this component, was missing from the assembly and was located on the grass runway near the initial point of impact.
Technical analysis of the trunnion's screw threads revealed no signs of stripping or deformation, but a large area of impact damage was noted on one side. Crucially, there was no evidence of locking wire present on the assembly. The holes in the retaining nut, which should have been secured with locking wire, were found to be clogged with hardened grease and debris, suggesting the condition had persisted for a long time.
Review of the maintenance records showed that the last documented work involving the removal of the shock absorbers occurred in March 2000. While this work was part of a mandatory service bulletin, subsequent undocumented maintenance did not include the necessary wirelocking of the retaining nut.
Findings
- The right main landing gear shock absorber became disconnected from the lower trunnion because the retaining nut was not correctly wirelocked.
- The absence of the locking wire allowed the nut to move and eventually fall off.
- The accumulation of hardened grease in the nut's locking holes indicated that the lack of wirelocking had likely existed for several years.