Boeing is checking out horizontal stabilizers on the 787 for improperly installed shims which could, if left uncorrected, potentially reduce the unit’s fatigue life.
In the meantime, flight tests have been temporarily halted, with ground tests now set to take place instead tomorrow on ZA002 and ZA003 – the only two 787s originally scheduled to be flying around now. ZA003 is now scheduled to undergo high intensity radiated field tests, while ZA002’s ground crew will 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.
Inspections are thought to be focused on the stabilizer rear spar. (Guy Norris)
The unfortunate “workmanship issue” concerns small gaps found around the intersection of the aft spar in the Alenia-built stabilizer with the center box that forms the structural join between the two horizontal tails. The stabilizers, manufactured at its Foggia facility in Italy, are made up of two monolithic co-cured horizontal units and the center box.The inspections will try to find if tiny shims used to fill gaps in the structure have been compressed. This will show where fasteners may have been over-torqued to complete assembly. Compressed shims and over-torqued fasteners have 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 and estimates the work will take up to eight days on any aircraft affected. The inspection does not apparently threaten the planned flight of ZA003 to Farnborough next month. It should be noted that workmanship issues have cropped up before with 787 parts from Alenia. As Dominic Gates points out in the Seattle Times, it is almost exactly a year ago now that Boeing was forced to issue a 'stop work' order at Alenia's Grottaglie facilty in Italy following the discovery there of wrinkled skins in the fuselage sections produced there.