Re: Concorde Loses #3 777 Would Dump!

From:         expaero@aol.com (ExpAero)
Organization: America Online, Inc. (1-800-827-6364)
Date:         21 Jun 95 02:56:56 
References:   1
Followups:    1
Next article
View raw article
  or MIME structure

>The following was posted to rec.travel.air.  Is it true?

>Unlike the Airbus aircraft the 777s fly by wire system uses only one
>implementation of the software, therefore if there is a software bug
>it will not be detected by another computer.

A very simplistic assessment.  This is potentially true, however, is it
any less true where different, i.e., multiversion software is used?
Worldwide software and hardware "experts" disagree on this issue.
European airworthiness authorities (JAA, DGAC) appear to favor
multiversion software implementations but the FAA gives no safety credit
use of multiversion software.  Academic studies seem to indicate that
common mode errors are just as likely to occur in multiversion software as
redundant systems which use the same software.  Dr. Nancy Levison,
University of Washington Professor has studied this issue extensively.
She posts often to Computer.Risks.  Mayber she can be pursuaded to
comment?

Beware simple answers to complex questions.