The National Transportation Safety Board is finishing up its initial examination into the deadly Southwest Airlines engine failure Thursday but many questions remain unanswered.
Investigators can't explain with certainty why the left engine of Southwest Airlines Flight 1380 malfunctioned when the plane was reaching over 32,000 feet. It's too soon to determine what happened, said National Transportation Safety Board Chairman Robert Sumwalt.
"I know people would want answers right away. We would do a very methodical investigation," Sumwalt told reporters Wednesday in Philadelphia. "Right now, we just want to document everything that we can."
They've interviewed the pilots, examined the damaged engine and collected video footage from passengers who lived through those 22 minutes of chaos.
They recovered the airplane's cockpit voice recorder and flight data recorder. And they are still tracking down debris from the engine.
As the NTSB leaves the Philadelphia airport, here is what's next for investigators:
The NTSB will look into how an interior crack on a fan blade could have led to the engine failure. Sumwalt said it was "certainly not detectable from looking at it from the outside."
The crack was found in a fan blade of the CFM International 56-7B turbofan engine that separated during the incident.
The blade had broken twice, where the blade attached to a hub and almost halfway through it, Sumwalt said.
One of the cracks was consistent with metal fatigue, he said.
Manufacturers regularly inspect engines for hidden cracks using X-ray machines or ultrasound devices the same kind of technology doctors use to check the health of expectant mothers.
Southwest Airlines said in an email Wednesday that workers did a visual inspection of the engine that failed. An ultrasonic inspection of engine was scheduled to take place this December.
The Federal Aviation Administration said Wednesday night it will issue a directive in the next two weeks requiring inspections of certain CFM56-7B engines. The directive will require an ultrasonic inspection of fan blades when they reach a fixed number of cycles.
A team of investigators are expected to travel to the airline's headquarters in Dallas next week and search through the plane's records.
"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 and what type of inspections were conducted," Sumwalt said.
Every engine manufacturer and airline monitors the engines "very, very closely," according to John Goglia, a former NTSB board member.
Sumwalt said they have not determined the age of the engine.
The NSTB wants to locate every piece of the damaged engine and then rebuild it.
Once they have all the pieces, a team will lay them all down on a hangar's floor and piece it back together, Sumwalt said.
CNN
