An urgent recommendation has been sent to FAA by the US National Transportation Safety Board (NTSB) to require operators to cut inspection intervals for Pratt & Whitney PW2037 engines to prevent uncontained failures.
The request is tied to an ongoing investigation of a 6 August incident at Las Vegas McCarran International airport where a Delta Air Lines Boeing 757-200 experienced an uncontained engine failure during its takeoff run.
Pilots of Flight 624 reported hearing a loud bang at the start of the takeoff, followed by indications that the right engine had lost power. The aircraft returned to the gate. None of the 166 passengers or four crew were injured and there was no fire.
Examination of the engine revealed the right engine's high pressure turbine second stage hub had failed, throwing metal fragments, including lugs, through the high pressure turbine casing and the bottom of the core cowl.
Investigators later learned that at least four other PW2037 second stage turbine hubs had experienced cracks in the blade retaining lugs, and that during a routine overhaul, American Airlines uncovered a PW2037 second stage turbine hub with cracks in two adjacent blade retaining lugs.
A second recommendation the NTSB issued today asks for continuing inspections of the hubs until the cause of previous cracking incidents is found and a corrective action is identified.
"These discoveries raise serious concerns and warrant immediate action by the FAA," says NTSB Acting Chairman Mark Rosenker. "A string of consecutively fractured blade retaining lugs could result in the simultaneous release of multiple blades, which would exceed the design capacity of the engine's cases and result in an uncontainment."