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Newsgroups: comp.risks
X-issue: 8.67
Date: Sun, 7 May 89 07:58:49 -0400
From: henry@utzoo.UUCP
Subject: Re: B-2 builders: Prototype need not apply

There is a subtlety here that people not intimate with military aviation may
not appreciate.  This is not as big an innovation as Northrop is claiming.  It
has been common for quite some time to build even the first one of a new
aircraft in "production" tooling.  Although it does save a lot of time, it also
contributes greatly to realistic testing.  Things like production processes
affect the result; it simply is not possible, in practice, for a hand-built
prototype to accurately represent production hardware.  Proper testing requires
hardware built with production tooling.  This practice started with the USAF's
"Cook-Craigie plan" techniques in the 1950s.

(Many of the critics quoted in the Philadelphia Inquirer article are making
fools of themselves because they don't understand this.)

Doing this also helps a lot when one wants to get production moving rapidly
after testing; part of Cook-Craigie is a scheme whereby early stages of
production ramp up fully while later stages concentrate on getting the first
few aircraft out the door, the hope being that any modifications that are
needed will not affect the early stages badly.

Inevitably, this sort of thing involves risk that production tooling will need
to be torn up and revised because testing finds problems, and that half-built
aircraft may need expensive revisions or even scrapping.  Efforts are made to
get the thing right the first time, and to get good test results as quickly as
possible.  Sometimes it works well; sometimes not.  As in other such production
innovations, after early successes there was a tendency for later projects to
get the outline right -- first aircraft built in production tooling, first
stages of production rolling early -- while forgetting important unorthodox
details like the emphasis on intensive early testing.  The result is failures,
which tend to be blamed on bad luck or the inherent difficulty of the problem
rather than on bad management.

(Another production innovation which suffered the same fate was concurrency:
designing all the pieces of the hardware simultaneously, relying on good
interface documentation to make sure they all work together.  When it works, it
gets hardware out the door much sooner than step-by-step methods.  It worked
well for the early ICBM programs because (a) they consistently funded multiple
parallel development efforts for anything deemed risky, and (b) they didn't
choose between them until hardware was available to be tested.  Many later
programs adopted concurrent development without these important (and expensive)
details, the result being a lot of failures.)

The ultimate end product of remembering the successes but forgetting the
details is what's going on at Northrop:  the conviction that it's possible to
get everything right the first time, so no modifications will be needed and
full-scale production can start immediately.  That *is* folly, but not because
there aren't any prototypes.
                                     Henry Spencer at U of Toronto Zoology

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