Engines Should Be Pulled From Service Pending Checks, Board Says

As a result of its ongoing investigation of an incident involving a Pratt & Whitney PW2037 engine experiencing an uncontained failure, the National Transportation Safety Board issued an urgent recommendation Thursday to the Federal Aviation Administration to require all Pratt & Whitney PW2037 engines be removed from service for inspection of the second stage turbine hubs when they have accumulated significantly fewer hours (10,880) and/or cycles (4,392) than the incident engine.

On August 6, 2008, Delta Air Lines flight 624, a Boeing 757-232 equipped with PW2037 engines, experienced an uncontained failure of the right engine’s high pressure turbine second stage hub at McCarran International Airport in Las Vegas, NV.

According to the pilots, at the start of the takeoff roll they heard a loud bang and observed that the right engine had lost power. The pilots rejected the takeoff and the airplane returned to the gate. All 166 passengers and the crew of four deplaned. There was no fire or injuries.

Examination of the incident airplane’s right engine revealed a hole in the bottom of the core cowl that was in line with a hole through the engine’s high pressure turbine. The inspection also revealed missing lugs and cracks in the turbine hub. Additionally, the Safety Board learned that at least four other PW2037 second stage turbine hubs have had cracks in the blade retaining lugs. And, NTSB has also learned that, during a routine overhaul, an American Airlines PW2037 second stage turbine hub with cracks in two adjacent blade retaining lugs was reported. The Safety Board has requested information on all of these hubs.    

"These discoveries raise serious concerns and warrant immediate action by the FAA," said NTSB Acting Chairman Mark V. 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. Preventive safety measures must be taken."

The NTSB issued a second recommendation Thursday that would require a continuing inspection schedule for the hubs until the cause of previous instances of cracking is found and corrective action is identified.

The Safety Board is still investigating this incident.

FMI Read The NTSB's Recommendation Letter (.pdf)