Boeing was changed to replace 777 engine covers before recent failures

Because the possible modifications to the 777’s external engine covers, commonly known as hoods, had several shortcomings, “Boeing has decided to redesign the fan hood instead of trying to modify existing fan hoods to address structural strength issues. “and moisture problems, an internal FAA document reviewed by The Wall Street Journal.

“Boeing will manufacture new fan hoods and provide service instructions to operators to remove and replace them,” according to the document, which is part of an updated routine on Aug. 6, 2020 on ongoing efforts in offices. of the Seattle agency. Boeing and the FAA declined to comment on the status of the engine coverage plan on Wednesday.

These changes to aircraft parts may require years of design, testing, and regulatory approvals. Some regulators and aviation safety experts are increasingly concerned about whether the engine covers are sturdy enough to withstand the impact of breaking and firing a fan vane during flights.

While rare, this damage to the engine cover has occurred in a handful of recent engine failures. Pilots train to land an engine-powered aircraft, which can be done safely, but large pieces of metal on the decks can endanger other parts of the aircraft – and passengers. According to some safety experts and reports from the National Transportation Safety Board, the engine testing process has not been fully explained by this possibility.

Jim Hall, president of the NTSB from 1994 to 2001, said recent incidents should have motivated regulators to look “very aggressively” at issues related to engine covers.

“I haven’t seen any signs of it being done yet,” he said.

Boeing said it will continue to follow FAA guidelines on 777 engine decks and is “committed to continued efforts to introduce safety and performance improvements throughout the fleet.”

An FAA spokesman said reducing the risk of engine fan blade blades that could damage the hood has been a priority – the focus of the agency’s directives after the 777 incidents in 2018 and the week past. FAA officials have said the agency was working with Boeing on a design change for another engine that failed on the 2018 Southwest Flight – killing a passenger – and reviewing the need for changes in other engines.

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

The engine crash of the 777 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 in about 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 manufactured by Pratt & Whitney on 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 to fan blades that broke and covered the engine covers.

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

Following the bankruptcy of the 2018 United 777, the FAA required that fan blades of the type of engine involved undergo special inspections of “thermal-acoustic imaging” –– using sound waves to detect signs of cracks –– each 6,500 vols. The engine that crashed over the weekend had made nearly 3,000 flights since its last inspection, according to people familiar with the matter.

On Monday, the FAA ordered immediate thermal-acoustic imaging inspections of fan blades on some Pratt & Whitney engines on some Boeing 777 aircraft. Pratt & Whitney is a unit of the aerospace company Raytheon Technologies Corp.

RTX 5.01%

But a design change to strengthen engine covers is a longer and more involved process. The FAA internal document said Chicago-based Boeing had presented its 777 engine coverage results 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 needed to keep the aircraft taking off. Engine covers that do not fall to the ground could generate aerodynamic drag, safety experts said. This could increase fuel consumption if the plane flies less efficiently, a concern for long flights over water with few options for emergency landings, said one such expert. The FAA document cites “fuel depletion” as a potential safety hazard.

Engine certification testing has focused on making sure broken fan blades do not fire to the side of an engine and puncture the aircraft’s fuselage. Less attention has been paid to the possibility that a blade may shoot forward and damage the front of the engine covers. These covers do not need to be joined during testing of how the motors cope with the broken fan blades, so that the blades remain visible.

“When you lose big pieces like that, that’s a danger,” said Jeffrey Guzzetti, former director of the FAA’s accident investigation division. “There was never any requirement to take that into account, but it never happened that much.”

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