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it planned to strengthen protective engine covers on its 777 jets months before a couple of recent serious failures, including one near Denver last weekend, according to an internal document from the Federal Aviation Administration.
The aircraft manufacturer and the regulator had been discussing possible solutions even longer, for about two years, according to people familiar with the matter. The talks began after two failures in 2018, one in a 777 operated by United Airlines Holdings. Inc.
and the other on a Southwest Airlines Co. 737.
Because possible modifications to the 777’s outer engine covers, commonly known as covers, had several shortcomings, “Boeing has decided to redesign the fan cover rather than attempt to modify the existing fan covers to address both resistance issues structural “such as moisture issues, according to the FAA internal document reviewed by The Wall Street Journal.
“Boeing will manufacture new fan covers and provide service instructions for operators to remove and replace,” according to the document, which is part of a routine August 6, 2020 update on efforts being made at the offices of the agency in the Seattle area. . Boeing and the FAA declined to comment on the status of the engine deck plan on Wednesday.
Such changes to aircraft parts can require years of design, testing, and regulatory approvals. Some regulators and aviation safety experts have become increasingly concerned about whether engine covers are robust enough to withstand the impact of a fan blade breaking and shooting outward during flights.
While rare, this engine cover damage has occurred in a handful of recent engine failures. Pilots train to land a plane that operates on a single engine, which can be done safely, but large pieces of metal on the decks can put other parts of the aircraft, and passengers, at risk. The engine testing process has not fully accounted for that possibility, according to some safety experts and reports from the National Transportation Safety Board.
Jim Hall, president of the NTSB from 1994 to 2001, said recent incidents should have prompted regulators to look “very aggressively” at engine cover issues.
“I have yet to see indications that this was done,” he said.
Boeing said it will continue to follow FAA guidance on 777 engine covers and is “committed to ongoing efforts to introduce fleet-wide safety and performance improvements.”
An FAA spokesperson said reducing the risk of engine fan blade failure that could lead to hood damage has been a priority, the focus of agency directives following the 777 incidents in 2018 and last week. . FAA officials have said the agency was working with Boeing on a design change for a different type of engine that failed on the 2018 Southwest flight, causing the death of a passenger, and reviewing the need for changes to other engines.
“Any proposed design change to a critical piece of the structure must be carefully evaluated and tested to ensure it provides an equivalent or improved level of safety and does not present unwanted hazards,” the agency spokesman said.
The 777 engine failure last weekend came shortly after the plane, as in one of the 2018 incidents, operated by United, took off from Denver International Airport. A seemingly weakened fan blade broke and appears to have cut a second blade roughly in half, according to the NTSB, which is leading the investigation. The engine cover was ripped off, leaving a trail of debris in the city below.
It resembled two recent failures of certain engines made by Pratt & Whitney in a subset of Boeing 777 aircraft: the 2018 United flight and one in December 2020 operated by Japan Airlines Co. Authorities in the US and Japan attributed both to the fan blades that are broken and battered motor covers.
In all three cases, the planes landed safely and without injuries.
After the 2018 failure of the United 777, the FAA ordered the fan blades of the type of engine involved undergo special “thermoacoustic imaging” inspections, using sound waves to detect signs of cracks, every 6,500 flights. The engine that failed over the weekend had made about 3,000 flights since its last inspection, according to people familiar with the matter.
On Monday, the FAA ordered immediate thermoacoustic imaging inspections for fan blades on select Pratt & Whitney engines on some Boeing 777 aircraft. Pratt & Whitney is a unit of the aerospace company Raytheon Technologies Corp.
But a design change to strengthen the engine covers is a longer and more complicated process. The internal FAA document said Chicago-based Boeing had presented the 777’s engine cover findings to FAA specialists in the Seattle area in early August.
Aircraft engines and their protective covers are supposed to contain broken fan blades and other metal parts, preventing them from damaging the structures necessary to keep the plane in the air. Separate engine covers that don’t drop to the ground could create aerodynamic drag, safety experts said. That could increase fuel consumption if the plane flies less efficiently, a concern for long flights over water with few options for emergency landings, one of these experts said. The FAA document cites “fuel depletion” as a potential safety hazard.
Engine certification testing has focused on ensuring that broken fan blades do not fly off the side of an engine and puncture the aircraft fuselage. Less attention has been paid to the possibility that a blade could shoot forward and damage the front of the engine covers. It is not necessary to put on those covers during testing of how motors cope with broken fan blades so that the blades remain visible.
“When you lose big pieces like that, it’s a hazard,” said Jeffrey Guzzetti, former director of the FAA’s accident investigation division. “There was never a requirement to consider this before, it just never happened that much.”
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