FAA Draft Mandate Targets Boeing 787 Shimming Issue
Note: This article has been updated with additional details on the wheelwelll shim issue and context on previously reported 787 production issues.
WASHINGTON—The FAA plans to order inspections for cracking near the wheelwell on “certain” Boeing 787-8s and -9s linked to improper shimming during production.
A draft airworthiness directive (AD) published May 10 proposes mandating Boeing instructions sent to operators in September 2020. The mandate would cover an unspecified number of aircraft, detailed in the Boeing alert-requirements bulletins. Affected aircraft would need repetitive high-frequency eddy-current inspections, the draft AD said.
“This proposed AD was prompted by reports that shimming requirements were not met during the assembly of certain structural joints, which can result in reduced fatigue thresholds and cracking of the affected structural joints,” the FAA explained. “Not meeting the shimming requirements during assembly of the [affected structure] results in excessive pull-up forces, fastener shanking, excessive burr heights in metallic members and the presence of metallic chips (foreign object debris) in fastened interfaces, which all degrade fatigue performance of any affected structural joints,” the agency added.
The issue affects joints in the aft wheelwell bulkhead—a large composite structure running transversely across the lower section of the fuselage close to the junction of the wing trailing edge. The cracking problem is focused on the forward edge of the bulkhead’s side fitting at Station 1290 on both sides of the fuselage, the side fitting outer chord and fail-safe strap areas, as well as the body chord itself, the draft AD said. The issue also affects the fastener heads and vertical beam clips common to the horizontal flange around the forward edge of the bulkhead body chord.
Boeing’s September 2020 instructions address the affected in-service fleet with a phased inspection plan. While flagged as requiring action by operators, the issue does not present immediate risk to the fleet.
Boeing identified and corrected the issue in production before the first 787-10 was delivered in early 2018, a source with knowledge of the situation said. The FAA said its mandate would apply to 79 U.S.-registered aircraft. American Airlines and United Airlines are the only two U.S.-based 787 operators; they have a total of 96 787-8s and -9s, Aviation Week Intelligence Network Fleet and Data Services shows.
“We had previously issued inspection guidance to our customers on these items, and fully support the FAA’s airworthiness directive making that guidance mandatory,” Boeing said in a statement.
Outside of alerting affected operators and the FAA, Boeing has not discussed the wheelwell issue publicly. But the company has been grappling with a series of production-quality shimming-related issues on 787s. The most prominent involves interior skin imperfections that create problems at fuselage barrel joints. The skin issue and was the driver behind a recent, five-month pause in 787 deliveries as the company worked to understand the problem and inspect aircraft in its inventory.
Inspections and rework have spread into the supply chain, with fuselage section and Section 41 forward-fuselage supplier Spirit AeroSystems acknowledging it is reworking some of its products before shipping them to Boeing’s 787 production site in Charleston, South Carolina.
“At Boeing’s request, we did an audit of the Section 41 and all the different areas that we build, and we identified some similar fit-and-finish issues that they had identified on other sections of the aircraft,” Spirit CEO Tom Gentile said on the company’s May 5 earnings call.
The wheelwell issue is the latest in a series of shim-related nonconformities linked to the 787 program. The aft wheelwell bulkhead, which is made by Korean Air and Kawasaki Heavy Industries (KHI), provides support at a highly loaded part of the fuselage structure. It also is designed to protect the surrounding airframe and systems from the high temperatures produced by the brakes and wheel friction of the main landing gear.
Korean Air, which together with KHI renewed its aft wheelwell bulkhead supply contract with Boeing in 2020, also produces the 787’s raked wingtip, flap-support fairing for wing and aft-body sections.