Boeing went on to replace the 777 engine covers before recent failures

As the potential modifications to the 777 outboard covers, commonly known as hoods, had several shortcomings, “Boeing decided to redesign the fan hood instead of trying to modify the existing fan covers to address both structural strength issues” and the moisture problems, according to the FAA internal document reviewed by The Wall Street Journal.

“Boeing will manufacture new fans and provide service instructions for operators to remove and replace the fans,” according to the document, part of a routine update on August 6, 2020 about ongoing efforts at the agency’s offices. in the Seattle area. Boeing and the FAA declined to comment on the status of the engine coverage plan on Wednesday.

These changes to airplane parts may require years of design, testing and regulatory approvals. Some aviation security experts and regulators are increasingly concerned that the engine covers are robust enough to withstand the impact of the fan blade breaking during flights.

Although rare, this damage to the engine cover has arisen in several recent engine failures. Pilots train to land an airplane operating on a single engine, which can be done safely, but large pieces of metal from the covers can put other parts of the aircraft – and passengers – at risk. The engine testing process was not fully considered for this 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 that recent incidents should have led regulators to look “very aggressively” at issues related to engine covers.

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

Boeing said it will continue to follow FAA guidance on 777 engine covers and is “committed to continuing efforts to bring safety and performance improvements to the entire fleet”.

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

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

The 777’s engine failure last weekend came just after the plane – as in one of United’s 2018 incidents – took off from Denver International Airport. An apparently weakened fan blade broke and appears to have cut a second blade almost 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 manufactured by Pratt & Whitney on a subset of Boeing 777 aircraft – the United 2018 flight and one in December 2020 operated by Japan Airlines Co. authorities in the U.S. and Japan assigned to blades fan caps that are broken and damaged.

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

Following the 2018 United 777 crash, the FAA determined that fan blades on the type of engine involved undergo special inspections of “thermo-acoustic imaging” – using sound waves to detect signs of cracks – every 6,500 flights. The engine that broke down 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 thermoacoustic imaging inspections for fan blades on some Pratt & Whitney engines on some Boeing 777 jets. Pratt & Whitney is a unit of aerospace company Raytheon Technologies Corp.

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But a change in design to strengthen the engine covers is a longer and more complex process. The FAA internal document said that Chicago-based Boeing presented the findings of the 777 engine cover to FAA experts in the Seattle area in early August.

Aircraft engines and their protective covers must contain broken fan blades and other metal parts, preventing them from damaging the structures necessary to keep the plane in the air. Loose engine covers that don’t fall to the ground can create aerodynamic drag, safety experts said. This can increase fuel consumption if the plane is flying less efficiently, a concern for long flights over water with few options for emergency landings, said one of those experts. The FAA document cites “fuel exhaustion” as a potential safety risk.

Engine certification tests focused on ensuring that broken fan blades do not reach the side of an engine and pierce the plane’s fuselage. Less attention has been paid to the prospect that a blade could shoot forward and damage the front of the engine covers. These covers do not need to be installed during testing of how the motors handle broken fan blades in order for the blades to remain visible.

“When you lose big parts like this, it’s a danger,” said Jeffrey Guzzetti, former director of the FAA’s accident investigation division. “There has never been a requirement to consider this before – it just never happened much.”

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