The engine that failed so catastrophically on a Boeing 737 plane operated by Southwest Airlines this week is not the only jet engine model with problems that have caught the eye of safety officials.
Like the engine on the Southwest jet, two others — one used on the Boeing 787 Dreamliner and another on some Boeing 767s — developed cracks. On Tuesday, the same day as the engine failure on the Southwest plane, the Federal Aviation Administration said Boeing 787 Dreamliners powered by Rolls-Royce engines could no longer be flown on ultralong, over-water flights.
The engines are produced by three different manufacturers, but the fact that all three have developed safety issues is prompting questions about the engines’ design, operation and their inspection procedures.
The worry is that the flaws are part of a trend as manufacturers push to develop ever more powerful and complex machines.
“We’ve gotten smarter,” said Richard Giannotti, an aerospace engineer. “We can design things to a very low margin with a lot of reliability data to back it up. But when we get to the ragged edge, it doesn’t take much for things to go wrong.”
He said that in the past, engines were designed with an abundance of precaution. “They don’t do that anymore. They’re trying to whittle down every last bit of material, every bit of weight. Thrust is king.”
But, Mr. Giannotti said, “there is such a thing as pushing things. We try to get right to the edge, with as little edge as possible, without stepping over.”
In the case of the Southwest engine failure this week, investigators say they are not only considering why a fan blade broke but why the engine housing failed to contain it. The shrapnel punctured a window in the plane, and a woman seated by it was partially sucked out. She was later pronounced dead.
The Federal Aviation Administration had already been close to ordering airlines using that particular engine, the CFM-56B, to conduct ultrasonic inspections. The agency appears to have been prompted to act after another Southwest 737 engine came apart in 2016, sending debris into the plane’s fuselage, wing and tail. The investigation into that incident is ongoing.
Late Wednesday, the F.A.A. said it was ordering those ultrasonic inspections. The engines on both Southwest planes, were manufactured by CFM International, a joint venture of General Electric and Safran of France.
The National Transportation Safety Board concluded that the inspections were insufficient to detect flaws in the disk of a CF-6 engine on an American Airlines Boeing 767 in late 2016. The plane was gaining speed on the runway in Chicago when the engine broke apart, sending metal fragments into the fuel tank and igniting a fire. The engine was manufactured by General Electric.
The chairman of the transportation safety board, Robert L. Sumwalt, said on Wednesday that the problems with the Southwest engine were worrisome because the agency had already discovered in the Chicago incident that some engine flaws were undetectable. “We are concerned about it,” Mr. Sumwalt said.
Inspections have also been ordered for the Rolls-Royce Trent 1000 engines that power a quarter of Boeing’s newest wide-body, the 787 Dreamliner, after cracks were found on rotor blades. But the F.A.A. went further and rescinded the operators’ approval to fly the airplanes any farther than 2 hours and 20 minutes from an emergency airport.
International long-haul carriers like United Airlines, Qantas Airways, Japan Airlines, Air New Zealand and British Airways purchased the Dreamliner over the past decade specifically for the plane’s ability to carry fewer people on longer routes more fuel efficiently. On extended flights over water, an airline could schedule flights on routes of up to five hours flying time from an emergency airport.
American and European regulators now say that cannot be safely accomplished. Should one Rolls-Royce engine fail, the higher power demand on the remaining engine could cause the second engine to fail.
“It’s pretty frightening,” said Mr. Giannotti, the aerospace engineer. “What is very clear is, there is a design flaw in the engine.”
LATAM Airlines, British Airways and Norwegian Air are three airlines that must now lease substitute airplanes or reassign other model aircraft to certain destinations, an expensive disruption.
“We are carrying out detailed precautionary inspections on Rolls-Royce Trent 1000 engines on our Boeing 787s to ensure we meet all the relevant regulatory requirements,” said Michele Kropf, a spokeswoman for British Airways. She declined to provide details of how the carrier was handling transoceanic routes on which it flies its 787s.
Although engine failure is not common, the bigger risk is when pieces of the motor fly out. “There’s a lot of mass behind them,” said Robert Benzon, a former investigator with the transportation safety board. “Because of the centrifugal forces involved, if they shoot out in the wrong direction, they can do anything.”
For more than a half-century, jet engines have taken the lead in advancing the capabilities of airliners, with each engine more powerful than the newest plane. They do more than just propel the plane through the sky; they provide power to the airplane’s demanding and complex systems.
The recent engine failures have certainly been disruptive and attention-getting, but do not necessarily indicate a trend, though Mr. Benzon said it might.
“It’s up to the industry and the entities, the investigators, the certification people, the F.A.A. in our case, to see if there is a trend and rectify it,” he said.
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