A Britten-Norman BN2A Mk III-2 Trislander was scheduled to operate a passenger flight from the Island of Jersey to the island of Guernsey, both in the Channel Islands. The pilot of the flight completed the pre-flight preparations including a walk-around inspection of the aircraft. No abnormalities were found during the inspection.
Close-up of the failed cowling fitting (Source AAIB © Operator) Once the passengers had boarded and the relevant checklists were completed the aircraft taxied to the runway, took off and set course for the short (21 nautical miles / 39 kilometres) flight to Guernsey. The flight to Guernsey was completed without remarks. The aircraft handled as normal, all indications were normal and there were no abnormal noises or vibrations apparent. The aircraft was stopped at its designated parking spot and once the aircraft was shut down the passengers disembarked. At was at this time the ground staff observed the cowling on the rear (No 2) engine had become partially detached. The pilot was immediately informed and the airline's maintenance department was informed. They investigated why the cowling had become partially detached and found that the front right-hand fitting on the lower section had pulled out of the fibreglass and was missing. This caused a loss of rigidity in the cowling assembly, resulting in the movement of the upper cowling. As a result, two clips, securing the upper and lower cowling sections together become undone on the right-hand side. The resulting movement was enough for the upper cowling to make light contact with the propellor blades, leaving rub marks on the blades that required repair, prior to further flight.
The failed cowling fitting (Source AAIB © Operator) The maintenance organisation that conducted the repairs of the cowling stated that it was not unusual for cracks to appear on cowlings of a certain age (like on the incident aircraft). However, this was the first time that it had resulted in the loss of one of the front fastener fittings. As the fitting was lost over water it was not recovered, and it was, therefore, impossible to determine the exact cause of the failure. Details of the event were included in the operators' continuation training syllabus. It was deemed not necessary to perform a fleet check of the fittings as the security of the engine cowlings is part of the daily inspection of the aircraft. The pilot of the aircraft submitted an Aircraft Accident Report Form to the Air Accident Investigation Branch detailing the events, described above. The AAIB Bulletin that was published as a result of that report was the basis for this blog., it is accessible by clicking on the .pdf file below;