What happened
On 11 October 2013, a Britten-Norman BN2A Mk III-2 Trislander, registration G-RLON, was operating a commercial passenger flight from Jersey to Guernsey. The flight, which carried 15 passengers and one crew member, proceeded without any noticeable issues or abnormal vibrations. However, upon arrival in Guernsey and during the disembarkation process, ground personnel identified that the cowling on the number two (rear) engine had become partially detached.
The investigation
The investigation focused on the structural integrity of the engine cowling, which consists of upper and lower fibreglass clamshell components. Investigators found that a front right-hand fitting on the lower section of the cowling had pulled out of the fibreglass and was missing. This loss of a fastener caused a reduction in structural rigidity, which allowed the upper half of the cowling to move. This movement was sufficient to cause the upper cowling to strike the propeller blades, resulting in minor damage and rub marks that required subsequent repair.
While the repair organization noted that cracks in cowlings are common in aircraft of this vintage, they confirmed this was the first instance where a failure led to the loss of a fastener fitting. The pilot reported that no abnormalities were detected during the pre-flight walk-around or during the flight itself.
Findings
- The failure of a single fastener fitting on the lower engine cowling section led to the incident.
- The loss of the fitting caused the upper cowling to lose its connection to the lower section on the right-hand side.
- The resulting movement of the cowling caused contact with the propeller blades, leading to minor damage.
- No injuries were sustained by the crew or the 15 passengers on board.