Chris Johnson, Index
Ariane 5 Case Study
- Error stemmed from redundant code!
m) The inertial reference system of Ariane 5 is essentially common to a system which is
presently flying on Ariane 4. The part of the software which caused the interruption in the
inertial system computers is used before launch to align the inertial reference system and,
in Ariane 4, also to enable a rapid realignment of the system in case of a late hold in the
countdown. This realignment function, which does not serve any purpose on Ariane 5, was
nevertheless retained for commonality reasons and allowed, as in Ariane 4, to operate for
approx. 40 seconds after lift-off.