Re: F-22 Raptor software problem

["peter koch" <peter.koch.larsen@gmail.com>]

On Feb 28, 8:44 am, Keith Thompson <k...@mib.org> wrote:
> "peter koch" <peter.koch.lar...@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.
>
Yes - that makes far more sense. I had a very difficult time (!)
believe that the problem had anything to do with timezones.

/Peter