Re: F-22 Raptor software problem

[Keith Thompson <kst-u@mib.org>]

"peter koch" <peter.koch.larsen@gmail.com> writes:
> On 26 Feb., 05:47, Hyman Rosen <hyro...@mail.com> wrote:
>> It's being reported (Slashdot, via CNN) that twelve of these
>> planes had their navigation and communications completely shut
>> down as they crossed the international date line while flying
>> from Hawaii to Japan. I believe much of the plane's software
>> is in Ada, but I have no details as to what caused the error.
>
> It surprises me that the software had problems dealing with this
> problem in the first place. Why anyone uses "calender time" for
> anything but display purposes is simply beyond my comprehension.

I'm only guessing, but I doubt that the error was caused by using
local time.  My suspicion is that the error occurred not when crossing
the International Date Line (which is crooked, as you can see on a
map), but when crossing the 180th meridian, when the longitude jumped
from 179.909 to -179.990.

I vaguely remember a similar problem with some air traffic control
software that was developed in the US, but wouldn't work in the UK,
because it couldn't handle a sign change in longitude.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
San Diego Supercomputer Center             <*>  <http://users.sdsc.edu/~kst>
"We must do something.  This is something.  Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"