An internal memo from the Federal Aviation Administration shows that as Boeing engineers disassemble the aircraft and discover new or more general problems, the manufacturing defects of the 787 Dreamliner are expanding.

The FAA memo, which was circulated internally on Monday and reviewed by the Seattle Times, pointed to new concerns about previously unreported deficiencies.

The memorandum also detailed the small gaps found in the entire aircraft structure: the junction of the large fuselage section, the front ballast bulkhead, and the structure around the passenger and cargo doors.

The FAA memo lists the safety conditions that affect aircraft currently in service worldwide, and points out that these tiny gap defects are believed to exist on more than 1,000 Dreamliner aircraft. These are not considered direct safety issues, but may cause premature aging of the airframe.

A Boeing spokesperson said on Friday: "We are looking at the undelivered aircraft from start to finish, and we have found areas where the manufacturing does not meet engineering specifications." "None of these issues are direct flight safety issues."

The spokesperson said that the aircraft currently in service can be inspected and reworked in future routine maintenance.

However, to complicate the process, the FAA memo states that Boeing does not have detailed configuration data for each aircraft and cannot know which aircraft may have defects.

It is not clear whether a solution that meets the FAA's requirements will further delay the delivery of the 787 until next year.

Such a delay may increase the total cost of getting the 787 program back on track, higher than Boeing’s previous estimate of $1 billion, and may face the risk of accounting write-offs in the fourth quarter.

The FAA’s internal memorandum concerned how Boeing reported to the FAA earlier this year that Mitsubishi Heavy Industries of Japan, which manufactures carbon composite wings for jet aircraft, found that the composite material was contaminated during the manufacturing process, which may be Weak the bond of the two composite parts together with an adhesive.

For example, when the stiffener is glued to the inside of the wing skin.

In the manufacturing process of the composite material, a carbon fiber tape impregnated with epoxy resin is laid on a mold and then hardened in an autoclave called an autoclave.

The bag is placed around the composite material to create a vacuum, and a sheet can be placed between the composite material and the mold to facilitate demolding when coming out of the autoclave. Contamination occurs because some bagging and mold release materials contain polytetrafluoroethylene-usually known under the brand name Teflon.

The use of PTFE, which leaves a residue after removal, does not meet Boeing's manufacturing specifications.

Initial tests conducted by Boeing and reported to the FAA in April showed positive results: Although the bond strength has been reduced, it is still within design limits.

However, the memo includes a new update at the end of last month, in which Boeing told the FAA that other major suppliers are now also discovering the same pollution, affecting not only the wings, but also the fuselage and tail.

In addition, further testing of small pieces of composite material now shows that, in some cases, the bond strength between contaminated parts is below the allowable design limit.

Boeing proposed to the FAA last month a method to assess the integrity of bonds in affected structures. But the FAA does not believe it. It responded that the proposed evaluation method has not been approved and has not been tested and verified.

"The FAA will conduct an investigation," the memo said.

Boeing’s communications team said on Friday that it did not immediately obtain detailed information about the pollution issue and was unable to comment on the specific issue before press.

A spokesperson for the FAA said: "We do not comment on ongoing discussions with manufacturers."

The FAA memo also highlighted the small gaps found in the structure around the passenger door and cargo door in the rear fuselage section built by Leonardo in Italy.

This is another example of the tiny gaps found in the aircraft structure during the final assembly. Previously, tiny gaps were found between the main part of the fuselage and the front pressure bulkhead. The front pressure bulkhead is a dome behind the nose of the aircraft. Shaped structural barrier for maintaining air pressure in the cockpit and passenger cabin.

As in the previous examples, the gap in the structure around the rear door of the fuselage is caused by the corrugation of the composite material at the joint.

The FAA pointed out that these differences between manufacturing structures and engineering specifications are not the result of poor mechanics, but the inaccuracy of the robotic equipment used to manufacture aircraft structures.

Such gaps can also occur in metal airplanes, usually filled with small pieces of material called shims during assembly. But somehow, Boeing suppliers ignored these gaps in the process of building the aircraft part.

The FAA stated that the lack of gaskets can cause skin fasteners to fall off.

The FAA memo states that Leonardo relies on mechanics to inspect his work when assembling structures, and quality inspectors have limited or no supervision. It also pointed out that the Italian supplier received two official notifications in 2018, stating that it had not conducted surface waviness inspections, and received two more notifications in 2020.

In this month’s update, the FAA stated that although Boeing provided a report claiming that the clearances around the rear fuselage door meet engineering requirements, it did not provide detailed manufacturing data on the assembly conditions of each aircraft.

The memo called the FAA "skeptical."

While waiting for the FAA to approve the inspection method, Boeing is repairing some aircraft.

A Boeing spokesperson said that its engineers have been trying to come up with a standard procedure to remove doors and inspect surrounding structures to meet FAA requirements, but because this takes too long, it has begun to modify some initial aircraft.

"We have been trying to determine a door disassembly and inspection method to see [whether it is possible] to plan a non-destructive inspection method to determine what we need to do in the future. This will take more time," the spokesperson said. "Therefore, we have begun to modify the door structure in the near future to try to be able to move forward on some aircraft."

At the same time, Boeing has suspended assembly of the rear fuselage in South Carolina while solving the problem.

The Wall Street Journal took the lead on Friday to report on the latest issue of the structure around the door. The Wall Street Journal quoted an unidentified person familiar with the plan as saying that it is increasingly likely that Boeing will resume delivery of the 787 "as of February or March at the earliest."

The FAA memo reviewed by the Seattle Times also provided an update on another 787 defect: an incorrect titanium alloy was used in certain parts of the fuselage part made by Leonardo in Italy.

Parts using this incorrect metal, including the fuselage frame and floor beam fittings, are installed on more than 450 Dreamliner aircraft. Boeing believes that the most critical installation is the fitting from the floor beam on the side of the fuselage area where the wings are connected to the fuselage frame.

The FAA stated that if two or more adjacent parts use the wrong titanium alloy, this may create unsafe conditions. Two airplanes with this direct safety issue were identified, and both All Nippon Airways jets were parked in Victorville, California.

All Nippon Airways agreed to ground the aircraft while Boeing repaired the aircraft. This work was completed last month.

Finally, the memo states that the FAA is still evaluating Boeing’s proposal to use statistical sampling to determine which aircraft are affected by the lack of gaskets and small gaps in connections.

The memo pointed out that more than 1,000 aircraft currently flying are affected, and the FAA is concerned about the lack of detailed assembly data for each aircraft. Boeing submitted an inspection proposal and stated that the process does not require FAA approval.

"We strongly disagree," the memo said. This stalemate about what level of inspection is appropriate remains a major stumbling block for Boeing to resume 787 deliveries.

Correction: This story was updated earlier on Saturday to correct the description of the composite material contamination problem. Teflon residue does not reduce the strength of the part. Conversely, when two such composite parts are bonded together with an adhesive, it reduces the strength of the connection.

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