Boeing has again halted 787 deliveries, this time after the Federal Aviation Administration declined to approve a Boeing-proposed algorithm related to inspections of a fuselage issue.

The move, which comes two months after Boeing resumed deliveries following a previous five-month pause, may reflect the FAA taking a more-proactive oversight role, says Michel Merluzeau, an analyst with aerospace consultancy AIR.

“The FAA is really not accepting what Boeing is proposing,” he says. “What we are seeing here is an audit of the processes at Boeing from the FAA… They are ensuring that everything that goes into this aircraft is by the book.”

Boeing 787-10. Boeing

Source: Boeing

Boeing 787-10

“Hopefully, this is just a case of everybody involved - Boeing and the regulators - being very mindful of getting everything perfectly squared away,” adds Richard Aboulafia, analyst with consultancy Teal Group. “The alternative explanation - another big issue needing to be resolved - would be painful.”

The FAA on 28 May confirmed Boeing voluntarily halted 787 deliveries.

“Boeing still needs to show that its proposed inspection method would meet FAA’s federal safety regulations,” says the US regulator. “The FAA is waiting for additional data from Boeing before determining whether the company’s solution meets safety regulations.”

Boeing had proposed to the FAA the use of an algorithm as part of the company’s plan for inspecting 787s for what the FAA calls a “shimming” issue related to 787 fuselages. The algorithm would have eliminated the need for Boeing to individually inspect multiple components.

The FAA requested Boeing supply data to support the algorithm. But the company has not supplied that data and the FAA says it was unwilling to sign off on Boeing’s method without addition validation, the agency says.

“Since the FAA has not approved Boeing’s proposal, Boeing chose to temporarily stop deliveries to its customers,” says the FAA.

Boeing says the latest pause does not relate to a 2019 fuselage “shimming” issue but rather a more-recent concern involving “skin flatness” of 787 fuselages. Shims can be one method of addressing skin-flatness problems.

“We are working to provide the FAA with additional information concerning the analysis and documentation associated with the verification work on undelivered 787s,” Boeing says. “We continue to work closely with the FAA in a transparent and timely manner. There is no impact on the in-service fleet.”

Boeing calls the delivery halt a “near-term” delay resulting from an issue for which the company had previously been cleared to resume 787 deliveries.

In 2019, Boeing identified a shimming issue affecting aft fuselage sections of 787s it said were produced that year. The company said the issue did not affect flight safety and that it addressed the problem in its production system.

Then, in October 2020, Boeing halted 787 deliveries until March due to what it described as a “skin-flatness” issue involving the same aft section of the jets’ fuselage, where fuselage sections join.

Skin flatness did not meet tolerances equivalent to the width of a human hair, Boeing said, adding that issue also did not affect flight safety.

Since resuming 787 deliveries in March, Boeing has delivered about one dozen of the jets, Cirium fleets data shows.

The FAA says it approved those jets not using Boeing’s algorithm but rather labour-intensive inspections.

The FAA has proposed two airworthiness directives (ADs) requiring inspection for and repair of potential shimming issues involving in-service 787s.

The first proposal, issued 7 May, says “shimming requirements were not met during the assembly of certain areas of the front spar pickle fork and front spar outer chord structural joints, which can result in reduced fatigue thresholds of the affected structural joints”.

The second proposal, dated 10 May, addresses shimming issues involving aft wheel well bulkhead structural joints.

News that Boeing halted 787 deliveries comes one day after the FAA said Boeing agreed to pay $17 million in penalties related to 737 Max and 737NG issues. The FAA says the manufacturer had installed instruments on 759 Boeing 737 Max and NG aircraft containing sensors that were not approved for that equipment.