Re: F-22 Raptor software problem

"peter koch" <peter.koch.larsen@xxxxxxxxx> wrote in message
news:1172666017.141406.173400@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Feb 28, 8:44 am, Keith Thompson <k...@xxxxxxx> wrote:
"peter koch" <peter.koch.lar...@xxxxxxxxx> writes:
On 26 Feb., 05:47, Hyman Rosen <hyro...@xxxxxxxx> 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

If the navigation computer was calculating velocity as a change in position
with respect to time and the time changed by a large (possibly negative)
amount, something could have gotten out of range and caused a software
crash. Bob


.

Quantcast