What happened
On 7 October 2018, a Czech Sport Aircraft Sportcruiser, registration G-CGEO, performed a routine landing at Fowlmere Aerodrome in Cambridgeshire. The flight, which began at Graveley Airstrip, was a private operation carrying one pilot and one passenger. The landing was described as smooth, and the aircraft taxied to its parking area without incident. However, upon exiting the aircraft, the pilot discovered a significant crack on the rear face of the right main landing gear leg. While the leg possessed enough residual strength to support the aircraft while parked, the damage was clearly visible.
The investigation
The AAIB examined the damaged landing gear leg by sectioning it into three parts. This inspection revealed that a piece of linear low-density polyethylene (LLDPE) plastic stretch film, used during the manufacturing process, had become embedded within the composite laminate. Laboratory analysis using FTIR spectroscopy confirmed that this trapped film was the same material used during production. The investigation established that during the lamination process, pressure from the inflatable tubes used to compact the glass fibre layers pushed the film into the leg's structure, where it became permanently trapped after the epoxy resin cured.
Findings
- The primary cause of the failure was a manufacturing defect where plastic stretch film was unintentionally trapped within the composite structure of the landing gear leg.
- This trapped material acted as a crack initiation site, allowing a crack to propagate through the central portion of the leg's structure.
- The structural integrity of the leg had been compromised, which was evidenced by the aircraft sitting 10 cm right-wing low during the month prior to the accident.
- A small area of fibre pinching at the rear of the leg section provided an additional point of weakness that failed during the landing at Fowlmere.