Operators of Airbus A220s are being instructed to conduct checks of the low-pressure compressor on Pratt & Whitney PW1500G engines, following two similar incidents involving failures on Swiss aircraft.
The incidents – on 25 July and 16 September – both occurred to Swiss A220-300s operating the Geneva-London Heathrow route.
Operators of the type have been told in a US FAA directive to perform initial and repetitive inspections of the compressor's inlet guide vane and the stage-one rotor.
Both Swiss A220 incidents involved failure of the stage-one rotor, resulting in the rotor being released from the low-pressure compressor case and damaging the engine.
"[Such] rotor failures historically have released high-energy debris that has resulted in damage to engines and [aircraft]," says the FAA directive.
It adds that, owing to similarity of design, it is extending the inspection regime to Embraer E2-family jets fitted with Pratt & Whitney PW1900G powerplants, because they are susceptible to the same condition.
The directive covers engines which have accumulated fewer than 300 cycles.
Initial inspections must take place within 50 cycles and within each subsequent interval of 50 cycles until the engine reaches this 300-cycle threshold.
They require borescope inspection of the rotor for damage or cracks at the blade tips, leading edge, and other areas, and checks on the inlet guide vane stem for misalignment. Any substantial findings must prompt replacement of the low-pressure compressor.
Pratt & Whitney issued a service bulletin on 23 September covering the borescope procedures. The FAA says the directive, which takes effect immediately, is an interim measure because the investigation into the Swiss A220 engine failures is still continuing.