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Southwest Airlines opposed a recommendation to inspect its fan blades after a 2016 accident in which one snapped off mid-flight, just like during the engine failure this week that killed a passenger.
A CFM56 engine on Southwest flight 1380 exploded over Pennsylvania on Tuesday, sending shrapnel into the fuselage of the Boeing 737-700 plane and shattering a window.
Bank executive Jennifer Riordan, who was in a window seat in Row 14 and was wearing a seat belt, was sucked partway through the gaping hole in the cabin and later died from her injuries.
It was the first death in a US commercial aviation accident since 2009.
Investigators said the fan blade that broke off mid-flight and triggered the fatal accident was showing signs of metal fatigue — microscopic cracks from repeated use.
The National Transportation Safety Board (NTSB) also blamed metal fatigue for the engine failure on Southwest Airlines flight 3472 on August 27, 2016 that was able to land safely in Florida.
The NTSB found the damage included a 12 centimetres by 40 centimetres hole that was found in the left fuselage just above the left wing, close to passenger windows.
No fan blade or inlet material was found in the hole and the cabin was not penetrated.
The 2016 incident led engine manufacturer CFM International to recommend in June 2017 that airlines conduct ultrasonic inspections of fan blades within 12 months on many Boeing 737s — the most popular airliner ever built.
The Federal Aviation Administration (FAA) proposed making the recommendation mandatory in August but never issued a final decision.
Southwest Airlines clashed with CFM over the recommendation, stating to the FAA in October that airlines needed 18 months to do the works and that only certain fan blades should be inspected, not all 24 in engines.
The Dallas-based carrier was not the only operator to ask for more time or suggest other changes.
The objections from Southwest and other airlines stem partly from the fact that carriers, while highly regulated, are not required to track each individual fan blade within an engine.
That, in turn, is making it harder for investigators to be certain whether the engine that exploded on a Boeing 737 on Tuesday was part of a group being targeted for inspection, according to the NTSB.
The blades, which sweep air backwards to help provide thrust, can be changed and repaired independently of the rest of the engine, meaning airlines that do not keep tabs have to examine more engines than anticipated, which adds time and cost.
It is unknown whether the FAA's original directive would have forced Southwest to quickly inspect the engine that blew up.
On Wednesday, the FAA said it would issue a directive in the next two weeks to require the ultrasonic inspections of fan blades on some CFM56-7B engines after they reach a certain number of take-offs and landings.
Blades that fail inspection would need to be replaced.
It was not immediately clear how many planes would be affected.
Last year, the FAA estimated that an order would cover 220 engines on US airlines.
That number could be higher now because more engines have hit the number of flights triggering an inspection.
Southwest has announced its own program for similar inspections of its 700-plane fleet over the next month.
Chief executive Gary Kelly said the plane that failed on Tuesday was inspected on the Sunday before and nothing appeared out of order.
A spokeswoman said it was a visual inspection.
NTSB chairman Robert 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.
AP/Reuters
Topics: accidents, air-transport, united-states