NTSB Identification: LAX99IA230.
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Scheduled 14 CFR operation of WILMINGTON TRUST C0
Incident occurred Friday, June 25, 1999 in SAN DIEGO, CA
Probable Cause Approval Date: 05/09/2001
Aircraft: Boeing DC-9-82, registration: N450AA
Injuries: 141 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
The crew heard a pop after the nose wheel lifted up during rotation on takeoff and a loss of power occurred on the right engine. An emergency was declared and an uneventful landing was completed. All of the third and fourth stage turbine blades fractured at the root and no fatigue marks were noted. The second stage turbine blades fractured at 1/2 to 2/3 span. All low-pressure turbine nozzle guide vanes exhibited significant leading edge rub and had meshed with adjacent turbine blade trailing edges. The low-pressure compressor drive turbine shaft fractured approximately 25 inches aft of the low-pressure compressor. This fracture was twisted and contained a large area of displaced and galled metal; coke/carbon was observed under the galled metal. The number 3 bearing was damaged; all balls were worn with flat spots up to 1/2 the ball circumference. Spalling was evident on the inner and outer race, but no race spinning was noted. The cage was intact, but worn. No evidence of oil starvation or overheating was evident. A flow check of the oil supply system to the number 3 bearing was completed with no blockage or flow anomalies detected. An inspection by an independent laboratory could not determine a cause for the bearing failure. The number 3 bearing had accumulated 12,487 hours since new.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: failure of the number three bearing. The resulting oil leak from the bearing led to coke/carbon buildup, which resulted in chafing of the turbine's low-pressure compressor drive shaft on the rear compressor seal tube and subsequent fracture of the drive shaft. Full narrative available
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