PHILADELPHIA -- U.S. airline regulators said Wednesday that they will order inspections of engine fan blades like the one involved in a failure that killed a woman on a plane that made an emergency landing in Philadelphia.
The Federal Aviation Administration said it will issue a directive in the next two weeks to require ultrasonic inspections of CFM56-7B engines after they notch a certain number of takeoffs.
The FAA decision came nearly a year after the engine's manufacturer recommended that airlines using certain CFM56 engines conduct ultrasonic inspections to look for cracks.
Federal investigators said initial findings show that Tuesday's aircraft emergency was caused by a fan blade that snapped off, leading to debris hitting the Southwest Airlines plane and a woman being partially blown out a window. She later died.
"This fan blade was broken right at the hub, and our preliminary examination of this was there is evidence of metal fatigue where the blade separated," National Transportation Safety Board Chairman Robert Sumwalt said.
Metal fatigue -- microscopic cracks that can splinter open under the kind of stress placed on jetliners and their engines -- was also blamed for an engine failure on a Southwest plane in Florida in 2016.
That led manufacturer CFM International, a joint venture of General Electric Co. and France's Safran SA, to recommend last June that airlines conduct the inspections of fan blades on many Boeing 737s.
European regulators last month required airlines flying in Europe to conduct the inspection, but the FAA had not yet required them despite proposing a similar directive in August.
The failure of the fan blade that snapped off as Flight 1380 cruised at 500 mph high above Pennsylvania set off a catastrophic chain of events that killed Jennifer Riordan, 43, of New Mexico and broke a string of eight straight years without a fatal accident involving a U.S. airliner.
Sumwalt expressed concern about such a destructive engine failure but said he would not yet draw broad conclusions about the safety of CFM56 engines or the entire fleet of Boeing 737s, the most popular airliner ever built.
It was unclear if the FAA's original directive would have forced Southwest Airlines to quickly inspect the engine that failed. Southwest Airlines Chief Executive Officer Gary Kelly said the engine had logged only 10,000 cycles since being overhauled. A cycle is one takeoff and one landing.
Before Wednesday's announcement, critics accused the FAA of inaction in the face of a threat to safety.
Robert Clifford, a lawyer who is suing American Airlines over another engine explosion that caused a fire that destroyed the plane, said the FAA should have required the inspections -- even if it meant grounding Boeing 737s.
"There is something going on with these engines," he said, "and the statistical likelihood of additional failures exists."
Kelly said it is too soon to say if Tuesday's incident is related to any other engine failures such as the one in 2016.
Tuesday's plane had flown 40,000 cycles since 2000, he said. Boeing delivered the plane to Southwest in July 2000, meaning that if the plane has been in continuous use it has made about three flights a day.
Kelly said the plane was inspected Sunday and nothing appeared to be out of order. A spokesman said it was a visual inspection and oil service of the engines. Sumwalt said, however, that the kind of wear seen where the missing fan blade broke off would not have been visible just by looking at the engine.
Meanwhile, the Southwest pilot who made the emergency landing Tuesday was being praised for her "nerves of steel" in helping to prevent further tragedy.
Tammie Jo Shults was at the controls of the Dallas-bound flight when it landed in Philadelphia, said her husband, Dean Shults. After shrapnel smashed a window and damaged the fuselage, the pilot took the twin-engine Boeing 737 that left New York with 149 people on board into a rapid descent as passengers using oxygen masks that dropped from the ceiling braced for impact.
Shults was among the first female fighter pilots in the U.S. military, according to friends and the alumni group at Shults' alma mater, MidAmerica Nazarene. She graduated from the university in Olathe, Kan., in 1983 with degrees in biology and agribusiness, university spokesman Carol Best said.
"She has nerves of steel," said Alfred Tumlinson, a passenger on Flight 1380, going on to say that he would "send her a Christmas card ... with a gift certificate for getting me on the ground."
Dean Shults also is a Southwest pilot, said Shults' brother-in-law, Gary Shults.
"She's a formidable woman, as sharp as a tack," said Gary Shults, a dentist in San Antonio. "My brother says she's the best pilot he knows. She's a very caring, giving person who takes care of lots of people."
Passengers said she walked through the aisle and talked with them to make sure they were OK after the plane touched down, carrying the body of Riordan as well as seven people with injuries.
Travelers said fellow passengers dragged Riordan back into the plane as the sudden decompression of the cabin pulled her part way through the smashed window.
On Wednesday, federal investigators were still trying to determine how the window that killed Riordan came out of the plane.
Riordan was seated in that row and wearing a seatbelt. Philadelphia's medical examiner said Wednesday evening that she died of blunt impact trauma to her head, neck and torso.
Information for this article was contributed by Terry Wallace and Claudia Lauer of The Associated Press; and by Samantha Schmidt of The Washington Post.
A Section on 04/19/2018