Engine Failure
During the take-off roll, a high-pressure turbine (HPT) blade in the right engine separated from its disc due to pre-existing fatigue cracks in the blade’s dovetail. The source notes that this blade configuration was prone to such cracking. The HPT blades were scheduled for removal 13 days later, as per a service bulletin aimed at reducing blade liberation events. The liberated blade struck an adjacent blade, causing it also to separate. These two blades then contacted the remaining 74 blades while still rotating, leading to overstress failures and release of additional fragments. Debris traveled rearward through the low-pressure turbine and out the rear of the engine, resulting in complete loss of thrust from the right engine. The flight crew heard a loud bang and felt a shudder, indicating rapid blade liberation and engine failure. The source states that given the failure location, detection of the crack during the engine’s lifespan was unlikely. The removal thresholds established by the manufacturer, CFM International, did not entirely prevent blade liberation, but fleetwide analysis showed that the CFM56-7B fleet remained within reliability targets and regulatory airworthiness guidelines.
Flight Crew Response
The engine failure occurred when the aircraft had reached decision speed V1. The source describes V1 as the critical point between aborting and continuing a take-off, and that an engine failure at this point represents the worst possible scenario for a multi-engine aircraft because safety margins are minimized for both abort and continue options. The crew responded quickly by continuing the take-off, declaring an emergency, identifying the problem, and following appropriate procedures. The effective coordination among the flight crew, cabin crew, air traffic control (ATC), and airport rescue and firefighting services (ARFFS) enabled the aircraft to safely return to Sydney Airport.