FAA Orders 787 Wing Splice Checks

The FAA has issued airworthiness directive AD 2026-17-02, effective 1 October 2026, requiring repetitive ultrasonic inspections of wing splice plates on the Boeing 787-8, 787-9 and 787-10 after a Boeing investigation found manufacturing errors and excessive preload forces at lower side-of-body splice joints.

The directive addresses a fatigue-crack risk that, left unaddressed, could weaken the primary wing structure until it can no longer sustain limit load — the structural design load condition that airworthiness certification requires an aircraft to withstand without permanent deformation.

What prompted the directive

The AD traces back to a Boeing investigation into how the 787's wing is joined to the centre fuselage section. At the lower side-of-body splice plates — the structural joints where the wing's lower chord meets the fuselage — the investigation identified two related problems:

• Shim gaps that may have exceeded engineering allowances during assembly, and
• High pull-up forces applied at fastener holes, which can seed fatigue cracks in the surrounding aluminium structure.

A shim is a spacer used during assembly to fill gaps between mating surfaces. When a shim gap is larger than the engineering allowance, the pull-up force needed to close the joint during fastener installation concentrates stress at the fastener holes. Repeated flight load cycles then act on that pre-stressed metal, and fatigue cracks can initiate earlier than the fatigue analysis underlying the certification basis assumed.

This failure mechanism is the structural cousin of the manufacturing-conformity issues that have driven previous 787 airworthiness actions, and it is part of a wider pattern of crack-inspection directives emerging from fleet-leader sampling and manufacturing investigations — a pattern The Flight Brief has covered in our reporting on the 747-8F freighter crack inspection AD and the 737 MAX bear strap crack inspection requirement.

What the AD requires

AD 2026-17-02 mandates repetitive ultrasonic (UT) inspections of the splice plates and associated structural elements at the wing-to-body join. The inspection scope covers:

• splice plates at the lower side-of-body joints;
• rear spar terminal fittings;
• lower chords;
• front spar terminal fittings; and
• jack pads.

Ultrasonic testing is the standard non-destructive inspection method for subsurface fatigue cracks in thick structural sections. A transducer coupled to the surface sends high-frequency sound waves into the metal; reflections from a crack surface are displayed on the instrument and interpreted by a certified NDT technician. Unlike visual or dye-penetrant methods, UT can find cracks that have not yet reached the surface — which is precisely the condition at issue here, where cracks may initiate at fastener holes beneath installed hardware.

For maintenance organisations, the AD is a Part 145 workflow item: aircraft must be inspected at intervals specified in the compliance table, with findings dispositioned through the approved structural repair manual or engineering-approved repairs before return to service.

Why the wing-to-body join matters

The side-of-body splice is primary structure — the load path through which wing bending loads transfer into the fuselage. Certification of transport-category aircraft under Part 25 of the FAA regulations requires the structure to sustain limit load without detrimental permanent deformation, and ultimate load — 1.5 times limit load — without failure. A fatigue crack at a splice plate fastener hole degrades the remaining load-carrying capability of the joint and reduces the residual strength margin below what the certification fatigue substantiation assumed.

That is why the FAA's unsafe-condition statement in the AD frames the risk in structural terms rather than as a nuisance finding: cracks at these locations, continuing to grow under repeated flight cycles, "could result in reduced structural integrity of the wing."

The 787's particular relevance here is its composite-heavy airframe. The wing-to-body join, however, includes the metal fittings and splice plates named in the AD, and the inspection technique — ultrasonic — reflects the need to examine installed structure without disassembly.

Affected fleet and operational impact

The AD applies to all 787-8, 787-9 and 787-10 aircraft — the entire in-service Dreamliner fleet. Operators will need to plan the inspections into existing heavy-check or line-maintenance windows where possible, but repetitive inspections by their nature recur, and compliance planning becomes a standing item in the maintenance programme for each affected airframe.

The practical MRO considerations are the familiar ones that accompany any recurring structural inspection requirement:

• NDT technician availability — certified UT technicians are a constrained resource, and a fleet-wide directive concentrates demand on inspection shops.
• Aircraft downtime — access to the splice plates, spar terminal fittings and jack pads may require panels opened and, in some cases, interior or fuel-tank access, which extends ground time.
• Finding disposition — any crack indication requires engineering assessment and repair before further flight, which is where AOG risk concentrates.

Operators with mature AD tracking systems — the compliance-management tooling we surveyed in our AD compliance tracking software buyer's guide — will absorb this into existing processes. Operators and lessees with smaller technical organisations should confirm which compliance option applies to their aircraft and whether any prior-shop-visit records satisfy the initial inspection requirement.

The wider pattern

AD 2026-17-02 joins a growing set of directives driven by manufacturing-conformity findings rather than in-service failures discovered the hard way. The FAA's post-2024 posture toward Boeing production quality — including the return of enhanced certification delegation oversight we covered when the agency restored Boeing's airworthiness certification authority — has increased the volume of structured investigations into assembly variability across the 737, 777 and 787 programmes.

The positive reading is that the system is finding these conditions through engineering investigation and fleet sampling, before they become in-service structural findings. The demanding reading is that assembly variability at shim-controlled joints was not caught at the source-inspection stage, and a repetitive inspection directive is the corrective net for a process gap that has since been addressed on the production line.

What to watch

1. Initial compliance results — the rate of crack findings across the first inspection cycle will indicate whether the risk was concentrated in specific production blocks.
2. Any terminating action — Boeing may develop a design change or process fix that allows the FAA to terminate the repetitive inspections; operators should watch for alternative methods of compliance.
3. Interval adjustments — the FAA may relax or tighten inspection intervals based on fleet findings, as it has done in prior structural AD programmes.

For 787 operators, the immediate action is straightforward: confirm fleet applicability, identify each aircraft's compliance deadline and get the UT inspections into the maintenance plan. Structural ADs on primary wing structure do not sit in the deferrable pile.