WASHINGTON — A rare failure in a metal-alloy disk spinning in the engine of an American Airlines jet sparked a fire that prevented takeoff, federal investigators said Tuesday.
The National Transportation Safety Board discovered quickly after the Oct. 28, 2016 incident in Chicago that a disk broke apart in the General Electric engine on the right side of the plane.
Within weeks, GE said there was a flaw in the common nickel-metal alloy used to manufacture the disk. But GE said the problem hadn't been detected in 30 years and there was only one plane at that time still using a disk from the same batch of alloy.
The board ruled that the internal manufacturing flaw likely wasn't possible to detect during manufacture or inspections between flights. The board urged the Federal Aviation Administration to develop new inspections for airliner engines to find internal disk cracks.
Robert Sumwalt, the board chairman and a former airline pilot, noted that nearly every airliner engine uses a similar metal alloy and this was the only reported failure in this way.
“It’s going to scare people," Sumwalt said. "The fact is this is a very, very rare failure."
Nobody was killed in the incident at O’Hare International Airport aboard a flight headed to Miami. But one passenger was seriously injured and 19 suffered minor injuries during the chaotic evacuation of the Boeing 767-300ER.
Investigators later found four pieces of the engine hurled up to a half-mile away on airport grounds. Holes were punctured in the right wing.
The pilots aborted the takeoff as passengers and crew members could see flames outside the window from rows 28 to 32. The pilots abandoned the takeoff at 147 mph, just before the limit of 154 mph to stop safely.
“They pulled this off spectacularly by having this rejected takeoff still stay on the runway," said Christopher Hart, a safety-board member. “I want to give kudos to the flight crew."
More about the engine fire and its aftermath:
Passengers moved from the right to the left side of the plane before it stopped moving, witnesses told investigators. Then passengers rushed the exit doors before the plane came to a halt about 3,775 feet from the end of the runway, and the cabin filled with smoke, investigators said.
Flight attendants had reported a loud noise – like a blown tire – while rolling down the runway before the plane fishtailed.
Flight attendants had trouble using the plane's phones to consult with pilots and notify them about evacuating. American Airlines has 13 different types of phones, including two for the 767. The type on the accident plane required the flight attendant to read a number on the back of the handset and then dial it, which the flight attendant said she dialed mistakenly.
“Even though there were mistakes, the majority of the flight attendants remained calm and did the job that they were required to do and trained to do, which was to put the safety of the passengers first," said Bella Dinh-Zarr, a safety-board member.
Kevin Brickner, American’s vice president for safety and operations, said in a statement to that board that flight attendants took the right steps to focus on evacuating the plane despite difficulties communicating with pilots.
“American empowers all crew members with the discretion to order an evacuation for safety purposes, and, under the exigent circumstances with visible smoke and fire, it was clearly appropriate for the cabin crew to initiate the evacuation without delay,” Brickner said.
American is enhancing training with mockups of each specific type of intercom phones installed on its fleet, he said.
“American Airlines has a robust safety culture, sound training programs for pilots and flight attendants, and well-proven operational and maintenance procedures,” Brickner said.
Emergency slides were blown toward the rear of the plane before the engine was shut down. One passenger in seat 20B told investigators he tumbled getting off the bottom of the slide where there was no one to help him. He was seriously injured when he was knocked over by the thrust from the engine.
American Airlines didn't have a separate checklist for engine failures on the ground, in contrast to an engine fire in the air, which could have urged pilots to shut off a second engine that wasn't on fire during an evacuation, investigators said. The board recommended the airline develop one.
Flight attendants told passengers to leave their bags behind. Despite passengers screaming “fire, open the door,” at least a couple of passengers refused to comply with flight attendants.
One man insisted on carrying a bag over his head. A woman struggled briefly with a flight attendant in the burning plane to keep her large bag.
“There needs to be something done with bags,” a flight attendant told investigators. “One passenger came running up the right aisle with a bag over his head. A flight attendant from the back was trying to get it away from him. The man kept yelling, ‘I’m taking it with me.’”
The board recommended FAA develop better counter-measures to prevent passengers from bringing carry-on bags with them during an evacuation. Airline officials agreed that the industry should develop better standards for carry-on bags, to avoid puncturing evacuation slides.
Crews train to evacuate planes within 90 seconds. Investigators found that after the plane halted, exit doors began opening after 15 seconds. The first passengers left within 31 seconds and all were out within 2 minutes and 11 seconds.
The fire scorched the outside of the plane, charring insulation blankets and melting windows before ultimately melting the wing. But Chicago fire investigators removed side panels and ceiling panels in the cabin from rows 28 to 35, and found no flames had gotten inside the plane.