After U.S. regulators had announced extra inspections, and Japan suspended her use of Boeing jets, Boeing Co has revealed it recommended suspending the use of 777 jets with the same type of engine that shed debris over Denver at the weekend.
The moves involving Pratt & Whitney PW4000 engines came after a United Airlines 777 landed safely in Denver on Saturday local time after its right engine failed.
United said the next day it would voluntarily and temporarily remove its 24 active planes, hours before Boeing’s announcement.
In a statement, Boeing said that it is “actively monitoring recent events related to United Airlines Flight 328.”
“While the NTSB investigation is ongoing, we recommended suspending operations of the 69 in-service and 59 in-storage 777s powered by Pratt & Whitney 4000-112 engines until the FAA identifies the appropriate inspection protocol.”
Boeing said 69 of the planes were in service and 59 were in storage, at a time when airlines have grounded planes due to a plunge in demand associated with the COVID-19 pandemic.
The manufacturer recommended airlines suspend operations until U.S. regulators identified the appropriate inspection protocol.
The 777-200s and 777-300s affected are older and less fuel efficient than newer models and most operators are phasing them out of their fleets.
According to the National Transportation Safety Board (NTSB), the initial examination of the plane indicated most of the damage was confined to the right engine, with only minor damage to the airplane.
The board also said the inlet and casing separated from the engine and two fan blades were fractured, while the remainder of the fan blades exhibited damage.
Japan’s transport ministry ordered Japan Airlines Co Ltd (JAL) and ANA Holdings Inc to suspend the use of 777s with PW4000 engines while it considered whether to take additional measures.
The ministry said that on Dec. 4, 2020, a JAL flight from Naha Airport to Tokyo returned to Naha due to a malfunction in the left engine.
Japan Transport Safety Board said on Dec. 28 that it had found two of the left engine’s fan blades were damaged, one from a fatigue fracture. The investigation is ongoing.
United is the only U.S. operator of the planes, according to the Federal Aviation Administration (FAA). The other airlines using them are in Japan and South Korea, the U.S. agency said.
Japan said ANA operated 19 of the type and JAL operated 13 of them, though the airlines said their use had been reduced during the pandemic. JAL said its fleet was due for retirement by March 2022.
Pratt & Whitney, owned by Raytheon Technologies Corp, said it was coordinating with operators and regulators to support a revised inspection interval for the engines.
An official at South Korea’s transport ministry said it was waiting for formal action by the FAA before giving a directive to its airlines. The U.S. agency said it would soon issue an emergency airworthiness directive.
Korean Air Lines Co Ltd said it had 16 of the planes, 10 of them stored, and it would consult with the relevant authorities.
In February 2018, a 777 of the same age operated by United and bound for Honolulu suffered an engine failure when a cowling fell off about 30 minutes before the plane landed safely. The NTSB determined that incident was the result of a full-length fan blade fracture.
Because of that 2018 incident, Pratt & Whitney reviewed inspection records for all previously inspected PW4000 fan blades, the NTSB said. The FAA in March 2019 issued a directive requiring initial and recurring inspections of the fan blades on the PW4000 engines.