DGCA: Piston Seals Linked Pratt A320neo Engine Failures

Fractured mid-turbine frame (MTF) piston seals have been linked to about half of the Pratt & Whitney PW1100G-JM engine failures reported by Indian carriers that damaged low-pressure turbines (LPTs), leading to a Pratt service bulletin recommending inspections, India’s Directorate General of Civil Aviation (DGCA) said.

Providing an update on the A320neo engine issues plaguing its operators, DGCA said the repetitive check is helping identify seals with excessive wear before the they fail. “A number of engines have been removed based on this inspection,” the agency said in a Jan. 12 update.

The long-term fix is a more durable blade, which Pratt has developed and is installing on new engines and making available to operators for the in-service fleet.

DGCA has ordered India’s Go Air and Indigo to fast-track introduction of modified engines to eliminate the LPT blade-fracture risk and several other issues plaguing their A320neo fleets. In the meantime, “mitigation measures put in place,” including the inspections, seals, and use of a less aggressive “alt-climb” procedure “will help in containing the engine failures on-wing,” DGAC said.

The agency in November ordered IndiGo to ensure its entire fleet of PW1100G-JMs contain the modified standard by Jan. 31 following four in-flight shutdowns within a week. LPT failures leading to operational disruptions jumped in 2019, DGCA said an a previous update, totaling 17 through July globally, including seven within India, compared to six and five, respectively, in all of 2018.

The new update gives the airline until May 31, and said the number of engines it will need has climbed to 135 from 120, to account for engines removed following seal inspections “and other reasons,” DGCA said. “No aircraft with [an] unmodified engine in [IndiGo’s] fleet shall be allowed to fly after that,” it added.

Pratt, Airbus and Indigo proposed a revised deadline of July 1, 2020, but DGCA pushed for a month earlier.  he U.S. FAA has ordered all engines to have modified blades by mid-December 2020. EASA has a de-pairing mandate in place and is expected to mandate fleet-wide removal in a subsequent airworthiness directive.

The LPT issue is one of several that has plagued PW1100G-JM operators, hitting Indian carriers particularly hard. Part of the reason is India’s demanding operating environment, which regularly exposes engines to sand, dust, and high ambient temperatures.

Indigo’s problems were exacerbated by standard operating procedure that had pilots climbing at maximum thrust settings, increasing strain on the engines. DGCA linked at least a dozen engine failures to the practice. In response, Indigo adopted the alt-climb procedure late last year.

DGCA said Indigo’s entire fleet has at least one modified engine, and 70% of all engines are expected to be the new standard by the end of March.

IndiGo has 103 Pratt-powered A320neos in service and 49 on order, Aviation Week’s Fleet Services database shows. Last year, the airline confirmed that 280 more A320neos in its backlog will be powered by CFM Leap-1As.

Sean Broderick

Senior Air Transport & Safety Editor Sean Broderick covers aviation safety, MRO, and the airline business from Aviation Week Network's Washington, D.C. office.