By David Shepardson and Alwyn Scott
WASHINGTON/SEATTLE (Reuters) - A fire on an American Airlines passenger plane as it was taking off from Chicago's O'Hare International Airport last week was sparked when the right engine broke apart, the U.S. National Transportation Safety Board said on Friday. The investigative update shed new light on a rare "uncontained" engine failure, in which pieces escaped the engine housing, that has been the talk of aviation circles since the incident on Oct. 28.
Pilots applied brakes to the Boeing 767-300 jetliner bound for Miami and aborted the takeoff of Flight 383. The engine failure caused a fuel leak that resulted in a fire under the right wing. The incident led to emergency evacuation of 161 passengers and nine crew, but no serious injuries.
The plane, built in 2003, experienced the failure about 6,550 feet (2,000 meters) after beginning its take-off and came to a full stop at 9,225 feet (2,800 meters), about 27 seconds after the engine failure, the NTSB said in an interim report.
Investigators looking for what caused the General Electric CF6-80 engine to fail are focusing on a high pressure turbine disk that broke apart.
One piece hit a UPS warehouse facility, about 3,000 feet (900 meters) from the runway, after slicing through a portion of the wing and traveling over the fuselage. The majority of the disk was recovered, and during laboratory inspection showed features consistent with fatigue cracking, the NTSB said.
The disk had gone through 10,984 cycles, or take-offs and landings, and had a life limit of 15,000 cycles. Review of the engine maintenance and manufacturing records and processes was continuing, the NTSB said, adding that additional examinations of the disk would focus on the cracking.
GE said the engine was manufactured in 1998. The failed disk was made of Inconel 718, an alloy used in aviation for decades, GE said. The CF6 engine is used on current Boeing 767 freighters and the KC-46 tanker used to refuel military planes in flight.
Uncontained aircraft engine failures are rare. GE said it had not suffered an engine failure caused by a problem with the Inconel 718 disk in more than 30 years. The CF6-80C2 has been in service for more than 30 years and has an in-flight shutdown rate of 0.004 percent over 400 million hours of flight.
The rotating disk "operates in one of the most harsh environments of a jet engine, especially at aircraft take-off," GE said in a statement.
American Airlines declined to comment.
The fire prompted 130 delays of departing flights and 170 inbound flights within two hours, according to flight-tracking website FlightAware.com.
(Additional reporting Jeffrey Dastin in New York; Editing by Frances Kerry and Dan Grebler)