Boeing 777 has dainty feet

From:         ncm@netcom.com (Nathan Myers)
Date:         10 Jul 95 16:36:53 
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I have heard recently that the new Boeing 777 jetliner, described in recent
news reports as "skating through the approval process", has a little problem
that might be interesting to RISKS readers.

It seems that an important part of the landing gear is too weak, and will get
"used up" (through metal fatigue), and need to be replaced annually. While
this is probably not a safety problem, it's an extra expense (frequent
inspections and replacements) and an embarrassment.

Unfortunately, fixing it isn't just a matter of making the part stronger; it
would then be bigger and heavier, affecting fit, balance, and nearby parts.
This sort of problem is familiar in the "shakeout period" of all previous
jetliners, but it's surprising that it showed up so late in the approval
process.  (A previous 7?7 has a nonlinearity in the landing gear linkage that
caused an oscillation when trying to close the doors; it was fixed by an
appalling hydraulic "patch" that cancels feedback during the nonlinear portion
of the cycle.)

How did this mistake get all the way through Boeing's legendary engineering
process?  The 777 is the first commercial Boeing to have been modeled entirely
on computer before construction.  Apparently the part is precisely a factor of
two weaker than it should have been.  Does this smell like a structural model
entry error?  I have been unable to find out more about the source of the
error, and would welcome more detailed information.

Maybe the RISK is in streamlining your engineering process so well, and
eliminating so many of the more common mistakes that would have caused delays,
that you are already getting final FAA approval before the booboos that only
time can reveal are noticed.  Or maybe the RISK is just that better
communications can leak word of embarrassments few would have known about
otherwise.