[LINK] F-22 Raptor stumped by International Date Line

[Tom Worthington]

  t 07:35 AM 28/02/2007, Stilgherrian wrote:
> >From http://www.dailytech.com/Article.aspx?newsid=6225 ...   On a 
> 12 to 15 hours flight from Hawaii to Kadena Air Base in Okinawa, 
> Japan. The U.S. Air Force's mighty Raptor was felled  by the 
> International Date Line (IDL)....

It is a little difficult to see what the bug could be. The military 
use "Zulu" time, known to civilians as Coordinated Universal Time 
(UTC) or colloquially as GMT 
<http://en.wikipedia.org/wiki/Coordinated_Universal_Time>. They don't 
use local time, so there should have been no change when crossing the 
international date line; neither the date nor time recorded on the 
aircraft would change.

The aircraft may have its local timing corrected by the Global 
Positioning System (GPS). The GPS system uses a clock slightly 
different to UTC, but this is a world wide standard and should not be 
effected by crossing the date line 
<http://en.wikipedia.org/wiki/Gps#GPS_time_and_date>.

What seems more likely is that the trip across the Pacific was longer 
than the software was designed to operate for. The software contains 
numerous timers and buffers. These are set back to zero when the 
aircraft systems are powered off. If the systems were operated for 
too long the timers reach their maximum values and then click over to 
zero. I recall the Patriot missile system had a problem of this sort.

ps: But I guess all that stuff I learnt working on Y2K and the GPS 
rollover at DoD may be of use after all 
<http://www.tomw.net.au/2006/ethics.shtml#safety>.  ;-)



Tom Worthington FACS HLM tom.worthington at tomw.net.au Ph: 0419 496150
Director, Tomw Communications Pty Ltd            ABN: 17 088 714 309
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