United Airlines Begins P&W 777 Engine Modifications Ahead of FAA Action

United Airlines has begun modifications to its fleet of Boeing 777s with Pratt & Whitney 4000-family engines that have been grounded since an engine failure over Denver in February.

The Chicago-based carrier, in collaboration with Boeing, has begun modifications to the aft bulkhead of the inlet cowl, United Senior Vice President of Flight Operations Bryan Quigley told pilots in an internal newsletter on October 6. In an unusual move, the work is being done ahead of an U.S. Federal Aviation Administration (FAA) airworthiness directive, posing some risk of the final mandate not matching the work undertaken by United. Quigley acknowledged this and said the airline is "over-communicating" the work it does with the regulator.

"We need to work ahead of the regulatory action in order to be able to return a large number of the aircraft back to the operation as quickly as we can," said Quigley, shedding light on why the carrier is taking the risk of possible additional modification work.

The Wall Street Journal reported in August that the FAA was unlikely to re-certify 777s with PW4000 engines until early 2022. The regulator was expected to mandate additional inspections and approve a proposed Boeing modification to the engine cover to prevent it from coming off in the event of a failure.

United has parked its 52 PW4000-powered 777-200s — more than 70 percent of its 74-aircraft strong 777-200 fleet. Many of those aircraft are configured in a high-density layout for the airline's Hawaii and hub-to-hub domestic flights that, without the jets, has put it at something of a capacity recovery disadvantage to its competitors as travelers — particularly domestic ones — have returned in droves.

The grounding contributed to "lower stage length and lower gauge versus 2019" in the second quarter that resulted in higher-than-forecast unit costs, Chief Financial Officer Gerry Laderman said in July.

"We'd like to see those aircraft back up in the air sometime late this year, early next year and be ready for full flying by the spring of next year when we believe that Europe is going to be fully open for business," United Chief Commercial Officer Andrew Nocella said of the 52 777s in September.

All PW4000-powered 777s globally have been grounded since the engine failure on a United jet scattered debris over Denver almost eight months ago. No one was injured and the aircraft only sustained minor damage, but the FAA quickly moved to ground the jets and mandated emergency inspections. The National Transportation Safety Board (NTSB), in its preliminary report in March, found evidence of fatigue fracture on one of the two fan blades that broke off from the engine.

Other areas of focus for United to return the 777s to the skies include ultrasonic and thermal acoustic fan blade inspections, inlet cowl and fan cowl thermography inspections, and inflight fire modifications, said Quigley. He did not say which of these steps were completed and which still underway.

United and Pratt & Whitney did not respond to request for comment on the modifications.