NTSB: American Airlines Engine Failure Attributable to Fatigue • Airways Magazine

MIAMI — The National Transportation Safety Board (NTSB)issued an Investigative Update of American Airlines flight AA383, which caught fire on runway 28R at Chicago O’Hare International Airport after aborting its take-off.

The report states that the right engine number 2 stage high pressure turbine (HPT) disk failed and fractured into at least four pieces. A large disk fragment landed in an UPS warehouse located about 2,920 feet (890m) from the aircraft.

Recovered stage 2 HPT disk pieces (Credits: NTSB)

According to the NTSB, the incident occurred while the Boeing 767-300 was accelerating for takeoff through 128 Knots-Indicated Air Speed (KIAS) with the engines set at takeoff power thrust setting. Two seconds after the failure, the power levers were retarded at 134 KIAS and brake pressures began to increase as autobrakes activated and speedbrakes automatically extended.

The aircraft came to a full stop about 25 seconds later 9,225 feet (2,811m) past the runway threshold, with a fire below its right wing fed by a pool of leaked fuel. 161 passengers and nine crew were evacuated, with 20 passengers and one flight attendant reporting non-critical injuries.

The NTSB also informed that the stage two HPT disk of the right engine failed and fractured into at least four pieces. The 90% of the disk was collected and sent to Washington D.C. for further examination.

Fatigue crack location on a disk fracture surface. (Credits: NTSB)

Preliminary results so far show one of the fractures showed indications of fatigue cracking initiated at an internal inclusion near the forward side of the hub’s inner bore. Ongoing metallurgical examinations of the disk will focus on detailed characterization of the inclusion and the fracture surfaces, the NTSB said.

The aircraft involved in the incident (N345AN • MSN 33084 • LN 906) was built in 2003, and is among American’s youngest 767-300s. At the moment of the incident, the aircraft had logged 8,120 cycles and 50,632 flight hours.