Compressor Stall Problem Reported With A320 Engines

The National Transportation Safety Board's ongoing investigation into last week's downing of US Airways Flight 1549 has centered on the aircraft's two CFM International turbofans, which appear to have been knocked out simultaneously after an encounter with a large flock of birds. The NTSB is exploring all possible causes for the engines to lose power, however... and that investigation has revealed some interesting tangents.

As ANN reported Tuesday, passengers who flew on the same plane on January 13 -- two days before Flight 1549 ditched in New York's Hudson River -- reported a loud bang and temporary loss of power in the plane's number two (right) on their flight, which was attributed to a compressor stall. The NTSB has since confirmed those reports.

Now, Newsday reports that two weeks before that incident, the FAA issued an airworthiness directive on CFM56-5B engines... the same type that were on N106US, the A320 that ditched in the Hudson. That AD was related to, you guessed it, compressor stall incidents; specifically, the AD calls for more stringent inspections of engines which exceed upper operating temperature ranges when the throttles are rolled back from takeoff power.

Earlier this month -- before Flight 1549 -- General Electric spokesman Rick Kennedy told The Business Courier of Cincinnati there had been 10 reported cases of compressor stalls on A320 family aircraft since April 2008, each lasting "a second or two." In one of those cases, both engines on an Air France A320 suffered apparent compressor stalls shortly after takeoff.

CFM is a joint venture of GE Aviation and French consortium Snecma.

At this time, these revelations appear to have little to do with what felled Flight 1549 on January 15. Both pilots onboard the airliner say they saw a large flock of birds immediately before the engines flamed out, and were unable to maneuver to avoid it. Neither have reported any prior engine anomalies.

That seems to follow with early results of the NTSB's investigation. "We have not found any indications of anomalies or malfunctions with the aircraft from the time it left the gate in LaGuardia... to the point at which the pilots reported a bird strike and a loss of engine power," said Board spokesman Peter Knudson on Tuesday.

Furthermore, analysis of the aircraft's right engine has revealed broken turbine vanes, consistent with impact with foreign matter... like with one or more large birds. Crews are still working to recover the plane's left engine from the floor of the Hudson River.

Newsday adds that salvage crews were seen Tuesday circling several areas of the A320's nose section with greasepens, "apparently to indicate possible bird strikes."

(Image by Gregory Lam)

FMI: www.faa.gov, www.ntsb.gov