A source at BAE Systems – which has the maintenance contract for RAN Sea kings at Nowra – suggests that all accounts to hand of the Nias Incident point to a catastrophic gearbox or rotor brake failure which would effectively stop the rotor in mid-air.

The reported sudden changes in engine pitch would be firstly the transmission bolts shearing to protect the engine, then the engine shutting down as it red-lined. Being engaged in back-to-back intensive operations means that this Sea King was well past its regular scheduled maintenance, but still within its servicable window.