Pratt & Whitney and Airbus are working on a mitigation plan to correct recently discovered issues with PW1100G-JM geared turbofan (GTF) high pressure compressor (HPC) parts that have led to several in-service incidents on Airbus A320neos and triggered an emergency order from the European Aviation Safety Agency (EASA). EASA's order, issued February 9 and based on an Airbus alert to operators, required operators to ensure no aircraft had two of the affected engines on one aircraft, and banned all extended range twin engine operations (ETOPS) flights using any affected engines, effective immediately.
Pratt said the issue covers 43 engines on 32 aircraft, including 11 A320neos with two affected engines. Another 55 engines from the affected population have been delivered to Airbus, Pratt said in a February 11 statement. Deliveries of Pratt-powered A320neos have stopped.
"Pratt & Whitney, in coordination with Airbus, will present to regulatory authorities this week a proposed mitigation plan for the modified configuration," the engine-maker said. "Pratt & Whitney will be in a position to provide greater detail around the remediation plan and impact, if any, on its 2018 delivery plan, once the regulatory authorities address its proposed solution."
The issue stemmed from an engineering change implemented in mid-2017 to improve the durability of the PW1100G-JM engine's HPC aft hub knife-edge seal, Pratt explained. The modified engines began entering revenue service in December. Since then, Pratt said, there have been four in-service incidents—either in-flight shutdowns (IFSDs) or rejected takeoffs—linked to the problem.
"While 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 [engine serial number] P770450, are more susceptible to IFSD," EASA explained in its directive.
Airbus has delivered 113 PW1100G-JM-powered A320neo-family aircraft to 18 customers. Indigo, with 32 Pratt-powered A320neos in service, operates the largest fleet of the new-generation Airbus narrowbody. Neither Pratt nor Airbus identified any of the affected operators.
The knife-edge seal problem is the latest of several issues that have hampered the GTF program. Pratt has installed several fixes aimed at improving reliability. It is not clear if the latest issue is linked to any previously identified problems or related modifications.