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New FAA directive targets PW1100G compressor problems

The Federal Aviation Administration has ordered airlines to replace components in the compressors and turbines of Pratt & Whitney PW1100Gs turbofans, which power Airbus A320neo-family aircraft.

The orders address corrosion concerns and issues with the engines' "knife edge seal" – the same seal that caused several inflight shutdowns earlier this year.

Those shutdowns prompted a grounding of PW1100G-powered A320neos.

"This [directive] was prompted by reports of in-flight engine shutdowns and aborted takeoffs as the result of certain parts affecting the durability of the rear high-pressure compressor… rotor hub knife edge seal," says one directive.

That order requires airlines to address the issue by replacing "diffuser case air seal" assemblies and vane assemblies in the second stages of high-pressure turbines in affected engines.

The FAA calls the knife-edge seal fix an "interim action" while P&W develops a solution. The problem arose because knife edge seals were allowing slightly too much air to pass through the engine.

P&W tells FlightGlobal it developed a fix "based on a design with which the company has significant experience".

"The situation was investigated by Pratt & Whitney and the company worked with Airbus, regulators and our customers to release a revised configuration to correct [the] issue in mid-February," P&W says. "We restarted engine deliveries back to Airbus by end of February. As of May 2018 we are caught up on our engine deliveries to Airbus."

P&W says 43 in-service engines were affected. Airlines returned all of those to P&W, which provided unaffected spares in return, it says.

The other directive orders airlines to replace the "front hub" of PW1100G high-pressure compressors – a measure that comes in response to a corrosion report.

"The [high-pressure compressor] front hub exhibited deposits that could not be removed using standard procedures and worsened over time," says the directive. "This condition, if not addressed, could result in uncontained [high-pressure compressor] front hub release, damage to the engine and damage to the airplane."

Carriers must replace the parts by mid-April, or within 6,180 cycles since the engine was new or five years since shipped, the FAA says.

In the USA, only Hawaiian Airlines and Spirit Airlines operate PW1100G-powered A320neo-family aircraft, according to the Flight Fleets Analyzer database. Airlines worldwide operate 227 Airbus narrowbodies with PW1100Gs, Fleets Analyzer shows.

Airbus also offers A320neo-family aircraft powered by CFM International Leap-1A turbofans.

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