Boeing is inspecting the horizontal stabilizers of all completed 787s for improperly installed shims that could potentially reduce the fatigue life of the unit if left uncorrected.

Boeing says the newly-discovered “workmanship issue” concerns small gaps found around the intersection of the stabilizer’s aft spar with the center box that forms the structural join between the two horizontal tails. The stabilizers, designed and manufactured by Alenia Aeronautica at its Foggia facility in Italy, are made up of two monolithic co-cured horizontal units and the center box.

The inspections are aimed at finding compressed shims where fasteners may have been over-torqued to complete assembly. This has the potential to alter load paths and load concentrations, thereby potentially reducing structural fatigue life. The company plans to perform rework and replacement where needed. If a shim — a ‘filler’ used to plug small gaps in completed structures — does require replacement, Boeing estimates the work will take up to eight days.

Flight tests have been suspended temporarily on ZA002 and ZA003, the only two 787 scheduled to fly on Thursday, June 24, while inspections continue. However “..the overall program schedule can accommodate the inspection process and the required rework without jeopardizing our delivery commitment,” says Boeing Commercial marketing vice president Randy Tinseth, commenting on his blog.

Boeing is reverting to ground tests for ZA003, which is now scheduled to undergo high intensity radiated field tests, while ZA002’s ground crew will take the opportunity of the inspection to perform regular maintenance. ZA001 is undergoing landing gear actuation tests prior to returning to flight tests with a new set of Trent 1000 engines. ZA004 continues its planned lay-up at Victorville, Calif., while having sensors installed for the coming load survey. Plans meanwhile continue for the start of flutter testing on ZA005, the first General Electric GEnx-1B powered 787.

Photo credit: Guy Norris