From: firstname.lastname@example.org (Nathan Myers) Organization: NETCOM On-line Communication Services (408 261-4700 guest) Date: 07 Apr 95 03:09:13
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[I posted this in comp.risks; somebody suggested it belonged here too.] 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.