Initial inspections of the Pratt & Whitney PW4000-112 engine that caught fire on flight UA328 on Saturday have found that Turbine Blade No11 sheared off at the root “likely caused by metal fatigue”.
Turbine Blade 10 was also sheared mid-way along its length, probably after being hit by Blade 11.
The incident hit the headlines on the weekend after the failure cause the fairing and nacelle to separate from the engine and land in a housing estate near Denver damaging property.
Debris from the engine also caused damage to the fairing on the wing root as it came off the aircraft.
All Pratt & Whitney powered Boeing 777s have been grounded as a precaution.