Installation Specs Confusing; So's The Explanation
Given the problematic nature of Boeing's relationship with its
suppliers on the oft-stalled 787 Dreamliner program... perhaps it's
understandable that many assumed the latest problem involving
fasteners on the composite-bodied airliner was the fault of one of
those contractors.
Well, you know what they say about 'assuming' anything.
According to The Seattle Times, up to 8,000 fasteners will need
to be replaced on each of the first 12 Boeing 787s now in various
stages of assembly at suppliers and Boeing's production line in
Everett, WA.
As ANN reported earlier this month, Boeing
inspectors found some fasteners projecting slightly from their
mounting holes, instead of lying flush with surrounding panels.
Boeing made the discovery near the end of the 57-day-long strike
by workers represented by the International Association of
Machinists. The news followed Boeing's announcement of yet another
delay for the Dreamliner's first flight, now tentatively scheduled
in early 2009.
The planemaker initially said the fasteners had been improperly
installed... but as it turns out, the blame for the glitch lies
instead in the hands of Boeing's own engineers, who wrote the specs
on the proper way to fasten sections of the plane's carbon-fiber
composite skin to its titanium structure.
Given the groundbreaking nature of the 787's construction,
Boeing had to write many series of instructions on how to join
various sections of the airplane together... and one set of those
specifications was apparently quite confusing.
An operations manager at a Boeing supplier plant -- who asked
not to be identified, out of concern for angering Boeing -- told
the Times he reviewed Boeing's instructions on how to join
composite materials to titanium, and found it was entirely possible
to misinterpret the spec.
"If I'm struggling and a 25-year design engineer is struggling,
how can you expect a mechanic to understand this?" said the
manager.
Even the simplified explanation of the problem is confusing. In
essence, Boeing's instructions on how to fasten the dissimilar
components differ, depending on which side -- composite or titanium
-- the fastener head would be on, and on whether the composite
piece needed to be drilled.
Measurements on the spec governing drilled composite pieces
being fastened to titanium panels -- with the fastener head on the
titanium side -- were inaccurate, as well as headache-inducing. If
a machinist followed the instructions, the fastener would protrude
slightly in its hole... as it wasn't made clear in the spec that a
bevel needed to be drilled first.
Got all that?
In any case, it's fair to say workers feel slightly vindicated
by the revelation. "I don't think it should be pushed on the
inexperience of the mechanics," said Joy Romero, VP of the 787
program for Vought Aircraft, which assembles aft fuselage sections
for the 787 in Charleston, SC. "It's more about the clarity of the
specifications and the confusion of the specifications."
Alas, it's a small victory... as quality control inspectors must
now locate and replace the errant fasteners. In many cases, that
includes ripping off insulation and interior panels already put in
place. Teams will need to work about a week at a time to find and
reinstall the fasteners in one aircraft.
ANN's Daily Aero-Term (05.10.24): Takeoff Roll
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