What happened
On 5 July 2009, a Britten Norman BN2A-Mk III Trislander, registration ZK-LOU, was performing a scheduled flight from Claris Aerodrome to Auckland International Airport. The aircraft was carrying one pilot and 10 passengers. Shortly after takeoff, while climbing through approximately 500 feet, the pilot noted unusual vibrations and a loss of synchronization between the engines. Following a loud bang, the pilot observed that the entire propeller assembly from the right engine had detached and struck the side of the aircraft.
The impact caused extensive damage to the fuselage, including the shattering of a passenger window and the detachment of a passenger door. While the aircraft's interior lining was pushed inward, causing 3 minor injuries to passengers, no one was seriously harmed. The pilot successfully managed the engine failure and performed a landing at Claris Aerodrome.
The investigation
Investigators examined the right engine's crankshaft and the damaged fuselage. The inquiry established that the propeller assembly had separated because the crankshaft flange, which connects the hub to the engine, had fractured. Technical analysis revealed that the failure occurred at the flange's lightening holes.
Further scrutiny of the engine's history showed that the crankshaft had been part of a component pool and had inadvertently exceeded its intended service life by approximately 11%. This discrepancy arose because of inaccurate service hour records from an overseas source in Indonesia. The investigation also looked into the maintenance and oversight of imported components and the accuracy of engine overhaul intervals.