Michael Amon

Flight 1549 engine prone to rare stall

Posted in Newsday by michaelamon on November 24, 2009


BY MICHAEL AMON
Jan. 21, 2009 p. A3

Before Flight 1549 ditched into the Hudson River, the Federal Aviation Administration had ordered heightened inspection procedures for the type of engine on that aircraft, saying it was prone to a rare type of stall, federal records show.

News of the Dec. 31 FAA Airworthiness Directive yesterday came as federal investigators said they were probing a Jan. 13 mid-flight engine stall on the Airbus A320 just two days before it crash-landed in the Hudson River alongside Manhattan on Thursday. The crew corrected the Jan. 13 problem in the air and safely completed its journey from LaGuardia Airport to Charlotte.

National Transportation Safety Board investigators want to talk to the pilot of that flight, said spokesman Peter Knudson. But he said nothing so far found has contradicted the working theory that a bird strike caused the plane’s engines to shut down Thursday. The directive warned such compressor stalls – a disruption of airflow into the engine causing an abrupt shutdown and violent shuddering of the plane – were “likely to exist or develop on” the CFM56-5B engine series, two of which powered Flight 1549. The warning was issued without a public comment period because “an unsafe condition exists,” the directive said.

Experts said such stalls are unusual in modern jet engines.

“We have not found any indications of anomalies or malfunctions with the aircraft from the time it left the gate in LaGuardia [last Thursday\] to the point at which the pilots reported a bird strike and a loss of engine power,” Knudson said.

The FAA directive ordered airlines to conduct detailed inspections when both engines record temperatures above a certain threshold and required the removal of at least one of those engines, even if it passes inspection. Officials would not say whether Flight 1549’s engine turbines underwent the required inspection with an optical instrument that allows maintenance workers to see inside the engine.

“It’s like colonoscopy, almost. You can look down in there and see if there is any damage to the blades,” said Ted Steffens, an airline maintenance expert with Expert Aviation Consulting in Indiana.

Rick Kennedy, a spokesman for GE-Aviation, which co-owns engine manufacturer CFM International, said 12 of the more than 3,000 CFM56-5B series engines had running temperatures above the threshold. All of them were older, like those on Flight 1549, and some were no longer in service.

About 10 aircraft with such engines experienced compressor stalls last year, leading CFM International to issue a safety bulletin, he said. But he said compressor stalls are unrelated to what occurred on Flight 1549.

Spokesmen for the FAA and US Airways declined to comment. Airbus did not respond to messages.

Aviation experts said the plane’s apparent engine stall problems were likely a coincidence with little significance for the probe. John Cox, a former US Airways pilot and now president of Safety Operating Systems, a Washington aviation consulting firm, said a susceptibility to compressor stalls “would not affect the ability to take a bird strike,” especially since the plane’s engines were not designed to handle ingestion of large birds like the Canada geese suspected in Thursday’s crash.

The cockpit voice recorder, flight data recorder and transcripts of air traffic control conversations show that the plane lost power to both engines about one second after the pilots reported a bird strike.

Meanwhile, the search for the plane’s missing right engine appeared to progress yesterday afternoon, as police boats spotted an object about the same size as the lost engine about 60 feet deep in the middle of the river off West 52nd Street, New York City police said. Divers are to resume the search today.

On a large salvage barge at Weeks Marine in Jersey City yesterday, inspectors opened the aircraft’s nose cone to examine electrical devices inside. They drew large red circles on the nose portion of the fuselage, apparently to indicate possible bird strikes.

Staff writers Andrew Strickler and Anthony M. DeStefano contributed to this story.

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