FAA Warns Airbus A220 Operators to Monitor Low-Pressure Compressor to Prevent Stall Risk
Airbus' A220s are powered by Pratt & Whitney's PW1500G engines. The powerplant has been the subject of the investigation after a series of engine failures on some A220 jets operated by SWISS International Airlines and airBaltic.
Checks revealed that the stage-one rotor of the low-pressure compressor was exposed to acoustic resonance, after a change to the vane schedule from a full-authority digital engine control software update.
Operators have been instructed to revert to a previous vane schedule with revised software. But the US Federal Aviation Agency says this can result in a lower stall margin for the compressor, resulting in deteriorated or dirty engines experiencing recoverable stalls at the top of the climb.
In a special bulletin, the FAA says two such stalls have occurred on the same PW1500G powerplant.
While it says this concern does not warrant an airworthiness directive, it is recommended that A220 operators “continuously monitor” the operating performance of the low-pressure compressor.
Pratt and Whitney has a method to monitor this performance, the FAA adds, which uses engine data provided by carriers, enabling the detection of deteriorated compressors before the onset of stalls.
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