Boeing moved to replace 777 engine covers for recent failures

As potential adaptations to 777 external engine covers, commonly known as casings, had various shortcomings, Boeing decided to redesign the fan cover instead of trying to modify existing fan covers to address the structural strength issues. internal FAA document reviewed by The Wall Street Journal.

“Boeing will manufacture new fan hoods and provide service instructions for the drivers to remove and replace the fan housings,” according to the document, which is part of a routine on August 6, 2020, regarding the efforts underway at the office of the agency in Seattle. . Boeing and the FAA declined to comment on Wednesday on the status of the engine cover.

Such modifications to aircraft parts may require years of design, testing, and regulatory approvals. Some aviation safety experts and regulators are increasingly concerned about whether engine hoods are robust enough to withstand the impact of blowing down a fan blade and outward shooting during flights.

Although rare, such hood damage has occurred in a handful of recent engine outages. Pilots practice landing a plane on one engine, which can be done safely, but large pieces of metal from lids can endanger other parts of the aircraft – and passengers. According to the safety experts and reports from the National Transport Safety Council, the possibility of the engine testing process has not been fully justified.

Jim Hall, chairman of the NTSB from 1994 to 2001, said recent incidents should have prompted regulators to look ‘very aggressively’ at engine hood issues.

“I have not seen it done yet,” he said.

Boeing has said it will continue to follow the FAA’s guidance on 777 engine covers, and is making ongoing efforts to implement safety and performance improvements in the fleet.

An FAA spokesman said reducing the risk of engine fan blade failure leading to hood damage was a priority – the focus of agency prescriptions after the 777 incidents in 2018 and last week. FAA officials said the agency was working with Boeing on a design change for a different type of engine that failed during the 2018 Southwest flight – killing a passenger and investigating the need for changes to other engines. .

“Any proposed design change to a critical piece of structure must be carefully evaluated and tested to ensure that it provides an equivalent or improved level of safety and does not pose unintended risks,” the agency’s spokesman said.

The 777 engine outage last weekend came shortly after the plane – as in one of the 2018 incidents, managed by United – took off from the International Airport. According to the NTSB, which is leading the investigation, a seemingly weakened fan blade broke and it looks like he shaved a second blade about in half. The lid of the engine was ripped away and left a trail of rubbish in the town below.

It looks like two recent failures of certain Pratt & Whitney-manufactured engines in a chassis of Boeing 777 aircraft – the 2018 United flight and one in December 2020 operated by the Japan Airlines Co. authorities in the US and Japan, both attributed to fan blades being chopped off and battered engine covers.

In all three cases, the planes landed safely without any injuries.

Following the failure of the United 777 in 2018, the FAA instructed that fan blades on the engine in question undergo relevant inspections of ‘thermal-acoustic image’ – using sound waves to detect signs of cracks – every 6,500 flights. According to people familiar with the engine that broke down over the weekend, it has made about 3,000 flights since its last inspection.

The FAA on Monday ordered immediate thermal-acoustic image inspections for fan blades on certain Pratt & Whitney engines on some Boeing 777 jets. Pratt & Whitney is a unit of the aviation company Raytheon Technologies Corp.

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But a design change to strengthen engine covers is a longer, more involved process. The internal FAA document said that Boeing in Chicago submitted its 777 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 structures needed to keep the aircraft afloat. Safety experts have said that stand-alone engine covers that do not fall to the ground can cause aerodynamic resistance. This can increase fuel consumption if the aircraft flies less efficiently. This is a problem for long-haul flights over water with few options for emergency landings, said one of these experts. The FAA document cites ‘fuel depletion’ as a potential safety hazard.

The certification tests of engines focused on making sure that broken fan blades did not shoot to the side of an engine and did not stick to the fuselage of the aircraft. Less attention was paid to the prospect of a blade shooting forward and damaging the front of the hoods. It is not necessary to fasten the lids during tests of how engines with broken fan blades cope so that the blades remain visible.

“If you lose such large pieces, it’s a danger,” said Jeffrey Guzzetti, a former director of the FAA’s Accident Investigation Division. “There’s never been a requirement to consider it before – it’s never really happened that much.”

Write to Andrew Tangel at [email protected] and Alison Sider at [email protected]