What happened
On 9 December 2006, a Piper PA-38-112, registration G-BNVD, was conducting a dual-instruction cross-country flight from Carlisle to Durham Tees Valley Airport. The landing was described as firm, though it did not involve a bounce or enough force to necessitate a formal report.
As the aircraft was taxiing at walking speed off the runway and onto the taxiway, the crew noticed the left wing appeared lower than the right. Shortly thereafter, the left main landing gear detached from the aircraft, causing the wing tip to strike the ground. There were no injuries to the two crew members on board, but the aircraft sustained significant damage, with the left wing and main landing gear rendered beyond repair.
The investigation
The AAIB investigation focused on the mechanical integrity of the landing gear assembly. While the crew initially suspected a crosswind had caused the wing dip, investigators found that one of the three bolts attaching the landing gear to the aircraft had unscrewed and fallen out. A search of the runway area recovered the missing bolt, which showed no evidence of locking wire or lock washers.
Engineers found that the remaining two bolts were properly secured with locking wire and showed no signs of being pulled from their barrel nuts. The investigation also reviewed the maintenance history, noting that the aircraft's attachment bolts had been replaced during an annual check earlier in 2006. The maintenance program followed the CAA Light Aircraft Maintenance Schedule (LAMS), which required inspections of the gear attachment bolts at 150-hour intervals, rather than the more frequent 100-hour intervals specified in the manufacturer's manual.
Findings
- One of the three bolts attaching the main landing gear to the aircraft had unscrewed and dropped out of its barrel nut.
- The aircraft's maintenance schedule required inspections of the landing gear attachment bolts every 150 hours, whereas the manufacturer's manual required checks every 100 hours.
- There was no requirement in the maintenance manual to remove the aircraft's weight from the landing gear when performing these specific security checks.