The chairman of the National Transportation Safety Board said Wednesday his agency was interviewing the crew of Southwest Airlines Flight 1380 and examining cockpit voice and data recorders as they investigate an engine failure that killed one passenger.
The flight from New York to Dallas made an emergency landing Tuesday in Philadelphia with heavy damage to the left engine, left wing and the fuselage where a passenger was partially sucked out of a window and later died.
In a field about 70 miles from Philadelphia Wednesday, investigators examined more pieces of the crippled plane hoping to be able to reconstruct the damaged engine.
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“We are finding, and residents are finding, additional pieces of engine cowlings,” said NTSB Chairman Robert Sumwalt.
The NTSB also released new video showing the extent of the damage to the left engine -- and the leading edge of the left wing -- hit by engine shrapnel.
In the early stages, investigators appear to have zeroed in on a missing fan blade in the engine --- finding signs of metal fatigue where the blade broke loose.
The fan blades function as a large propeller making the air accelerate at the front of the engine.
If the blades become worn or fatigued they can break -- a rare occurrence -- especially in the type of engine involved in Tuesday’s troubled flight, a CFM-56, the most popular jet engine in the world.
“The airplane and engine are workhorses of the fleet and they certainly have a good record, “said Tommy McFall, a veteran accident investigator who has worked for the NTSB and a major airline.
McFall said the NTSB will be looking not only at the Flight 1380 but also any other previous incidents.
In 2016 another Southwest Airlines plane lost a fan blade on a flight that landed in Florida -- and NTSB found signs of metal fatigue.
“If there have been other apparently similar modes of failure then they will be comparing these events and seeing if there are common threads,”, McFall said.
Investigators are also looking at the maintenance history for the plane involved in Monday’s incident.
Sumwalt said the NTSB would convene a maintenance group at Southwest Airlines headquarters in Dallas to begin examining records as a routine part of the investigation.
“They will begin to examine the inspection records for this engine and specifically for this fan section these fan blades to understand the inspection history,” Sumwalt said.
Southwest Airlines has announced it will perform ultrasonic tests on all engines in its fleet to check for signs of metal fatigue over the next 30 days -- out of what the company calls an abundance of caution.
Meanwhile --- investigators are also examining why a protective ring in the engine did not contain the damage -- as it is designed.
Both the engine maker CFM International, and the aircraft manufacturer, Boeing, said they are assisting the NTSB in the investigation.