Two days after a woman died and seven people were injured aboard Southwest Airlines flight 1380, the FAA has ordered inspections of fan blades on all CFM56-7B engines of the same type that were involved in Tuesday’s incident, NPR reported.
Meanwhile, information about the cause of death of Jennifer Riordan, the mother of two who was killed when she was partially sucked out a shattered jet window, has finally been released: Philadelphia’s medical examiner said Riordan was killed by blunt trauma to her head, neck and torso when she was partially blown out a cabin window shattered by engine debris. Federal inspectors say Riordan, 43, was wearing a seatbelt at the time of the accident.
So far, investigators have determined that the accident was caused by a propeller blade inside the engine tearing off midflight and wrecking the inside of the engine, showering the plane with the debris that broke Riordan’s window. The plane, which took off from New York, was forced to make an emergency landing in Philadelphia.
Bowing to the demands of outside airline safety experts, the FAA said late Wednesday that some 220 CFM56-7B engines used to power Boeing 737s must be ultrasonically inspected after a certain number of takeoffs. American Airlines has about 300 planes with CFM56 engines, while Delta Air Lines has about 185. The engines are produced by CFM, a 50/50 joint company of GE and Safran Aircraft Engines.
Separately, Southwest Airlines said it would carry out an inspection of its fleet over the next month.
The problem with the fan blade that broke off is that the “metal fatigue” discovered by the investigators would’ve been difficult to detect pre-accident – the only way to find it would’ve required an ultrasound inspection.
With the NTSB’s investigation ramping up, the Wall Street Journal reported Thursday that the agency is focusing on two issues:
- How did the propeller blade wear down?
- And why did the loss of a single propeller blade have such a devastating impact on the cowling (the engine covering that appeared damaged in flight photos) and the rest of the engine?
Should the agency find any issues requiring immediate attention, Robert Sumwalt, the chairman of the NTSB, promised that the board would issue “urgent safety recommendations” (the NTSB doesn’t have the power to compel action, only the FAA can do that).
“If we feel there is a deeper issue, we have the capability to issue urgent safety recommendations,” he said.
Engine coverings are coated in special protective materials to prevent an incident exactly like the one that unfolded on Southwest Flight 1380 – which is why the damage sustained by the engine is so alarming.
Historically, engine designers and maintenance crews have been on guard against internal parts shooting into the cabin or out the front of the engine. Kevlar shielding and other design elements are primarily intended to prevent such an event, called an uncontained failure.
But experts tracking the probe now are focusing on an apparent vulnerability in the cowling, which shouldn’t have been affected by the kind of internal failure that apparently occurred Tuesday.
Investigators have found numerous remnants of the cowling on the ground, including a large piece roughly 65 miles from where the plane touched down, Mr. Sumwalt said. “We are finding additional pieces” as more reports from the public emerge, he said.
A former airline engineering chief said the the incident suggests that aircraft manufacturers may need to reexamine how engines are reinforced.
Ray Valeika, a former maintenance and engineering chief at Delta Air Lines Inc., said the accident suggests traditional risk-reduction approaches may need adjustment. “To have a single blade split the cowling like that is concerning,” he said.
Among the issues likely to come under question is whether Southwest fully followed nonbinding recommendations for enhanced inspections by the engine maker.
Investigators are expected to delve into, among other things, whether ultrasound inspections were conducted as recommended in June 2017 by engine maker CFM International—a joint venture between General Electric Co. and France’s Safran SA . They are trying to determine whether the recommendations applied to the specific engine in the accident, according to people familiar with the details.
Unsurprisingly, representatives from CFM touted their safety credentials, saying the CFM is the safest and best-selling jet engine in a world.
The FAA had apparently directed air lines to conduct ultrasonic inspections of CFM engines after an alert from the company, but it’s unclear if such an inspection would’ve caught the defect that caused the propeller blade to break off. “It was on the interior part of the fan blade,” Sumwalt said, adding that it was “certainly not detectable from looking at it from the outside.”
NTSB investigators determined that a similar issue with metal fatigue caused an engine failure on another Southwest Airlines flight in August to 2016.
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