The European Aviation Safety Agency (EASA) has issued an Emergency Airworthiness Directive (EAD) that has lead to the grounding of specific Pratt & Whitney PW1100 GTF-powered A320neo/A321neo aircraft effective immediately.

Issued on Friday, February 9, the EAD said the measure was necessary after several A320neo Family jets reported In-Flight engine Shut-Downs (IFSD) and Rejected Take-Off (RTO) events. Affected PW1100G variants include: the PW1127G-JM, PW1127GA-JM, PW1130G-JM, PW1133G-JM, and PW1133GA-JM engines having Engine Serial Number (ESN) P770450 or subsequent.

"While the investigation is ongoing to determine the root cause, preliminary findings indicate that the affected engines, which have high pressure compressor aft hub modification embodied from ESN P770450, are more susceptible to IFSD. This condition, if not corrected, could lead to dual engine IFSD," EASA said.

Airbus said in a statement that it had extended full support to Pratt & Whitney in its investigations into "the root cause of this new finding." Citing sources at the European manufacturer, Reuters says Airbus has stopped test flights as well as deliveries of the PW1100-powered A320neo variant for the time being. Airlines and lessors have already been consulted, the report said, adding that new deliveries could be delayed by as much as six months.

According to Pratt & Whitney, the issue specifically pertains to the knife edge seal in the High-Pressure Compressor (HPC) aft hub on the PW1100G-JM engine.

"This issue is isolated to a limited subpopulation of engines," it said in a communique. "We have identified the potentially affected engines and communicated with our customers."

EASA's operational restrictions entail the grounding of aircraft with two affected engines pending repair/change out, the de-pairing of affected engines, and the discontinuation of Extended Range Twin-engine Operations (ETOPS) for aircraft fitted with affected engines.

Operators that have thus far been forced to ground select jets include IndiGo Airlines (6E, Delhi Int'l). According to The Economic Times, three of the Indian LCC's thirty-two A320neo have been taken out of service, by order of the Indian Directorate General of Civil Aviation (DGCA), pending remedial action. CNN reports Hawaiian Airlines (HA, Honolulu) has also confirmed that one of its A321neo is affected and that it has since been taken out of service.

As of February 12, ch-aviation research shows the following airlines have grounded A320/321neo aircraft: Air Astana (one A321neo), Air China (three A320neo), Hawaiian Airlines (one A321neo), HK Express (one A320neo), Indigo (three A320neo), LATAM Airlines (two A320neo), Lufthansa (one A320neo), Sichuan Airlines (three A320neo), Spirit Airlines (one A320neo), Tianjin Airlines (two A320neo), VietJetAir (one A321neo), Volaris (one A320neo), and West Air (China) (one A320neo).