Newsgroups: comp.risks
X-issue: 10.63
Date: Sun, 18 Nov 90 23:05:09 EST
From: henry@zoo.toronto.edu
Subject: MD-11 test flights over the pole

Interesting item in the 22 August issue of Flight International: the prototype
of McDonnell-Douglas's new MD-11 airliner (a DC-10 derivative) made a test
flight partly aimed at testing performance of navigation software in the
vicinity of the North Pole, making four passes directly over the pole and one
nearby.  On two of the pole passes, the flight-management computers were
deliberately "failed" to see if the backup equipment would function.  No
problems, they say.

(This is not as trivial as it sounds, because the vicinity of the poles is a
severe worst case for navigation algorithms.  The distance between degrees of
longitude goes to zero while latitude remains unaffected, trig functions are
pushed to extrema of their behavior, and there is a singularity in the
coordinate system at the pole itself.)
                                         Henry Spencer at U of Toronto Zoology