Re: Boeing 777 - Totally Irresponsible?

Date:         27 Dec 96 13:32:19 
From:         faurecm@halcyon.com (C. Marin Faure)
Organization: Northwest Nexus Inc.
References:   1
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In article <airliners.1996.2792@ohare.Chicago.COM>, "Bernie Gracy, Jr."
<bgracy@worldnet.att.net> wrote:

> The keynote speaker of the 1996 Pacific Northwest Software Quality
> Conference reviewed the 10^9 (ten to the ninth power) problem.  Years of
> testing a PC program are required to believe that it won't fail within a
> week of release.  To meet the FAA standard of 10^9 hours of failure free
> operation would require 100 years of testing assuming that one could
> execute 1 test/sec (there are about 10^7 seconds in a work-year).
>
> He went on to say that because of the millions of lines of code written
> for the 777 that it would be impossible to test all of the failure
> conditions, and therefore was irresponsible to design and deploy such an
> aircraft.  He vowed never to fly on one...
>
> How was the 777 tested?  Is it safe?  Or is it "unsafe at any airspeed?"

Following this logic, just about piece of machinery with a computer in it,
from an elevator to a car to an airplane can be considered "unproven."
For that matter, you can make a similar claim for a complex piece of
machinery that is purely mechanical if you take into account every single
component, down the tiniest lock washer, that could fail,the almost
infinite combination of stresses that can be put on the materials, and so
forth.

If the speaker quoted in the above post vowed never to fly on a 777
because of "unproven" software, he'd best stay off just about every plane
in operation today.  While they may not all be fly-by-wire, they all
incorporate flight computers, they all used computerized navigation
systems, just about all of them have some form of computerized crew
alerting systems, many of them have fly-by-wire engine control, etc.,
etc., etc.  Shoot, a computer flushes the toilets on half of them.

 The 777 "flew" in the Integrated Airplane Systems Laboratory for a full
year before the first plane was even rolled out the door.  Then there was
a year of flight testing, during which the "plane" in the laboratory
continued to be flown along with the nine airplanes in the flight test
fleet.  The 777 underwent the most extensive flight test program in
commercial aviation history.  The 757 and 767, for example, each had
flight test programs of about 1,500 flying hours.  The 777 test program
was over 3,500 flying hours.

But the bottom line is that there are two pilots up front who can take
over any time something appears to be malfunctioning.  The 777 has (I
believe) three modes of control, from fully automatic to "direct" which is
full control by the pilot.  The system redundancy in the plane is
phenomenal.  Despite the theoretical validity of the speaker's statement,
I would say the 777 is just the opposite of his conclusion: that it is, in
fact, the most reliable plane in the sky today.

C. Marin Faure
   author, Flying a Floatplane