The Federal Aviation Administration ordered airlines to inspect engines and restrict flights of other planes after Southwest Flight 1380’s fatal engine failure.
As airlines voluntarily speed up safety inspections after a fatal Southwest Airlines engine failure Tuesday, the Federal Aviation Administration announced it will order inspections within two weeks.
The action, however, followed months of haggling between the manufacturer and airlines over the deadline for completing inspections on engines common to the popular Boeing 737, an industry workhorse. The proposal resulted from a similar Southwest engine failure in August 2016.
Problems with fan blades occasionally breaking off, which typically result in unscheduled landing rather than passenger injuries, extend beyond the 737 and the engine manufacturer CFM International. An FAA order Tuesday immediately restricted flights of 787 aircraft with a certain type of Rolls-Royce engines, after « several engine failures » and reports of cracked fan blades.
The attention focused on fan blades followed an engine failure Tuesday aboard a Southwest flight from New York to Dallas. A passenger died after being pulled partially through a window the plane before being pulled back by other passengers.
Investigators from the National Transportation Safety Board have focused initially on a broken fan blade – number 13 of 24 – in the failed engine.
Cracking from metal fatigue, or a weakening of the metal from the heat and stress of spinning to push air through the engine, was visible on the broken stump, according to Robert Sumwalt, the safety board chairman.
But investigators must still determine what caused the fatigue and whether there was a manufacturing flaw, Sumwalt said.
The cracking wasn’t visible from the exterior of the fan blade, according to Sumwalt. That’s why airlines decided to speed up ultrasound inspections of fan blades, to spot problems before engines fail.
The FAA said Thursday it would issue its inspection order for CFM56-7B engines within two weeks.
“The directive will require an ultrasonic inspection of fan blades when they reach a certain number of takeoffs and landings,” the FAA said. “Any blades that fail the inspection will have to be replaced.”
Southwest, which flies 737 aircraft exclusively, had already announced after the Monday failure that it would inspect all the similar engines in its 700-plane fleet within 30 days. United Airlines executives also said during an earnings call Wednesday that they would inspect 698 similar engines in their fleet.
But Southwest also said the failed engine didn’t technically fall under the FAA inspection proposal in August.
Sumwalt couldn’t say Wednesday whether the engine qualified under the proposal because part numbers change over time. But he said investigators would track down the inspection status while studying engine maintenance records.
The FAA proposal resulted from an August 2016 engine failure on a Southwest flight from New Orleans to Orlando, which diverted to Pensacola, Fla. Engine debris tore a 5-inch-by-16-inch hole in the fuselage above the left wing, but didn’t injure anyone inside the cabin.
Even after the FAA proposal in August, airlines disputed how many engines were at stake. Southwest called FAA’s estimate of 220 engines needing inspection “vastly understated,” and United said the number could “be much higher.”
Southwest, for example, said it identified 109 engines qualifying for inspections. But the airline said without tracking blade numbers, it would have to inspect 732 more engines to comply.
Southwest, United and Delta Air Lines each sided with FAA’s proposed 18-month deadline to complete inspections. American Airlines suggested 20 months.
But CFM, which is jointly owned by GE and Safran Aircraft Engines of France, urged a 12-month deadline.
The FAA hadn’t acted on the proposal before the Tuesday incident.
Fan blades occasionally break for a variety of reasons. An object like a bird could fly into an engine. A manufacturing flaw might leave the metal weaker than intended, as happened with a disc in an American Airlines engine in October 2016. Or the routine heat and vibrations from rotating quickly enough to lift a plane into the air could snap a fan blade after 40,000 flights.
Al Sievers, a physics professor emeritus at Cornell University, warned that the length of the fan blades at more than a foot long might leave them vulnerable to breaking. He compared vibrations of the spinning blades to violin strings, and warned that if one fell out of tune it could grow worse until snapping.
“You can imagine bending the blade back and forth, back and forth until it hardens and snaps,” he said.
Federal investigators plan to test the Southwest equipment to determine whether a manufacturing flaw or usage led to the break, Sumwalt said.
But Sievers suggested the industry should test more broadly whether blades are failing because of defects or usage.
Concerns about fan blades are broader than the plane or manufacturer or airline.
The FAA on Tuesday restricted the flights of 787 Dreamliner aircraft with a certain type of Rolls-Royce engines to fly farther than 140 minutes from an airport, down from the previously approved 330 minutes. The order followed a similar directive in December from the European Aviation Safety Agency.
The European order followed an engine failure aboard a Scoot 787 that returned safely to Singapore airport. A fan blade had broken off after cracking from corrosion.
The planes are designed to fly with one engine. But regulators were concerned that after one engine failed, the higher thrust required of the remaining engine could lead to another broken fan blade that could leave the plane with neither engine working.
« The resultant blade vibration can result in cumulative fatigue damage that can cause blade failure and consequent engine shutdown, » the FAA said in ordering the flight restrictions.
The restrictions could disrupt 787 trips over oceans for the long-distance planes. Boeing said the safety orders could affect one-fourth of the 670-plane fleet, including 14 planes at U. S. airlines.
« If a durability issue is found, the blade will be replaced, » Boeing said in a statement. « This is a known issue and we will continue to work with Rolls-Royce, our customers and the regulators to fully resolve it.
