Boeing decided to replace 777 engine covers ahead of recent blackouts

Since the potential modifications to the 777 external engine cowls, commonly known as cowls, had various shortcomings, “Boeing decided to redesign the fan cowl instead of trying to modify the existing fan cowls to address both the issues. structural strength ”and moisture problems, according to the internal FAA paper reviewed by the Wall Street Journal.

“Boeing will manufacture new fan cowls and provide service instructions to operators to remove and replace fan cowls,” according to the document, which is part of an August 6, 2020 routine, updating on ongoing efforts at the agency’s offices in the Seattle area. . Boeing and the FAA declined to comment on the status of the engine cover plan on Wednesday.

Such modifications to aircraft parts can require years of design, testing and regulatory approvals. There is growing concern among some aviation safety experts and regulators whether engine cowls are tough enough to withstand the impact of a fan blade breaking and firing outward during high speed flights.

Although rare, such engine cover damage has occurred in a handful of recent engine failures. Pilots practice landing a single-engine plane, which can be done safely, but large pieces of metal from covers can endanger other parts of the plane – and passengers -. The engine testing process has not fully taken this possibility into account, according to some safety experts and reports from the National Transportation Safety Board.

Jim Hall, chairman of the NTSB from 1994 to 2001, said recent incidents should have prompted regulators to look “very aggressively” at the problems surrounding engine covers.

“I have yet to see any indication that this has been done,” he said.

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

An FAA spokesperson said reducing the risk of engine fan blade failures that could lead to hood damage was a priority – at the center of agency guidance following 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 on the Southwestern flight of 2018 – killing a passenger – and considered the need for a change to other engines.

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

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. An apparently 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 looked like two recent failures of certain engines manufactured by Pratt & Whitney on a subset of Boeing 777 aircraft – the United flight 2018 and one in December 2020 operated by authorities at Japan Airlines Co. in the United States and Japan. , both attributed to fan blades that broken and damaged engine covers.

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

After the 2018 failure of the United 777, the FAA required that the affected engine type fan blades undergo special “thermo-acoustic image” inspections – using sound waves to detect signs of cracks – all 6,500 flights. The engine that failed over the weekend had made around 3,000 flights since its last inspection, according to people familiar with the matter.

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

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But a design change to fortify the engine cowls is a longer and more complex process. The FAA internal document said Chicago-based Boeing presented its 777 engine cowl findings to FAA specialists in the Seattle area in early August.

Aircraft engines and their protective cowls are believed to contain broken fan blades and other metal parts, preventing them from damaging the structures needed to keep the aircraft in the air. Loose engine covers that do not fall to the ground could create aerodynamic drag, safety experts have said. This could increase fuel consumption if the plane flew less efficiently, a concern for long flights over water with few options for emergency landings, one such expert said. The FAA document cites “fuel depletion” as a potential safety risk.

The engine certification tests focused on the fact that broken fan blades do not spring out from the side of an engine and puncture the aircraft fuselage. Less attention has been paid to the possibility that a blade could pull forward and damage the front portion of the engine cowls. These covers should not be attached when testing how motors cope with broken fan blades so that the blades remain visible.

“When you lose big chunks like that, it’s a danger,” said Jeffrey Guzzetti, former director of the FAA’s accident investigation division. “There had never been an obligation to consider this before – it never really happened.”

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