About the F-22 software bug
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From: Pascal Obry on 4 Feb 2010 13:46 [Second attempt to post this message. Sorry if you reveived this multiple time, it seems this message never reached comp.lang.ada]. Just curious, does someone have information to share about this problem: << While attempting its first overseas deployment to the Kadena Air Base in Okinawa, Japan, on 11 February 2007, a group of six F-22 Raptors flying from Hickam AFB, Hawaii, experienced multiple computer crashes coincident with their crossing of the 180th meridian of longitude (the International Date Line). The computer failures included at least navigation (completely lost) and communication. The fighters were able to return to Hawaii by following their tankers, something that might have been problematic had the weather not been good. The error was fixed within 48 hours, allowing a delayed deployment.[24] >> >> I know that the F-22 is 90% of Ada. Is there some public information about this bug? Is that a design bug? Thanks, Pascal. -- --|------------------------------------------------------ --| Pascal Obry Team-Ada Member --| 45, rue Gabriel Peri - 78114 Magny Les Hameaux FRANCE --|------------------------------------------------------ --| http://www.obry.net - http://v2p.fr.eu.org --| "The best way to travel is by means of imagination" --| --| gpg --keyserver keys.gnupg.net --recv-key F949BD3B
From: Hibou57 (Yannick Duchêne) on 5 Feb 2010 01:51 On 5 fév, 07:42, Dennis Lee Bieber <wlfr...(a)ix.netcom.com> wrote: > > So far as I recall -- from some years ago -- it was an algorithm > problem handling position information wrap-around from crossing, as > mentioned, the International Dateline... -180.0 to +180.0 deg longitude. > > I didn't hear that they had to follow the tankers back -- was under > the impression once they managed to cross back heading east a reboot of > the navigation system started working again... > > -- > Wulfraed Dennis Lee Bieber KD6MOG > wlfr...(a)ix.netcom.com HTTP://wlfraed.home.netcom.com/ Do you know what was the pattern of this conception error ? You've said from some years ago : this was a known problem ? Wasn't solved since so long ?
From: Martin on 5 Feb 2010 03:30 On Feb 5, 6:42 am, Dennis Lee Bieber <wlfr...(a)ix.netcom.com> wrote: > On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...(a)obry.net> > declaimed the following in comp.lang.ada: > > > I know that the F-22 is 90% of Ada. Is there some public information > > about this bug? Is that a design bug? > > So far as I recall -- from some years ago -- it was an algorithm > problem handling position information wrap-around from crossing, as > mentioned, the International Dateline... -180.0 to +180.0 deg longitude. > > I didn't hear that they had to follow the tankers back -- was under > the impression once they managed to cross back heading east a reboot of > the navigation system started working again... > > -- > Wulfraed Dennis Lee Bieber KD6MOG > wlfr...(a)ix.netcom.com HTTP://wlfraed.home.netcom.com/ For some reason (that I don't get at all) lots of systems define long as -180 <= x <= +180 degrees. Having the potential to alias a position seems like a bad idea for a start, so when I've been coding such systems up, I've always spent a bit of time making it convert positions into the range -180 <= x < +180 degrees and using a proper ADT. I wonder if it was anything to do with that?... Cheers -- Martin
From: Ludovic Brenta on 5 Feb 2010 03:52 Martin wrote on comp.lang.ada: > On Feb 5, 6:42 am, Dennis Lee Bieber <wlfr...(a)ix.netcom.com> wrote: > > On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...(a)obry.net> > > declaimed the following in comp.lang.ada: > > > I know that the F-22 is 90% of Ada. Is there some public information > > > about this bug? Is that a design bug? > > > So far as I recall -- from some years ago -- it was an algorithm > > problem handling position information wrap-around from crossing, as > > mentioned, the International Dateline... -180.0 to +180.0 deg longitude.. > > > I didn't hear that they had to follow the tankers back -- was under > > the impression once they managed to cross back heading east a reboot of > > the navigation system started working again... > > > -- > > Wulfraed Dennis Lee Bieber KD6MOG > > wlfr...(a)ix.netcom.com HTTP://wlfraed.home.netcom.com/ > > For some reason (that I don't get at all) lots of systems define long > as -180 <= x <= +180 degrees. > > Having the potential to alias a position seems like a bad idea for a > start, so when I've been coding such systems up, I've always spent a > bit of time making it convert positions into the range -180 <= x < > +180 degrees and using a proper ADT. > > I wonder if it was anything to do with that?... I would have thought a longitude was really a mod 360, shifted by -180 for display purposes? For fractional degrees (i.e. minutes and seconds), make that mod (360 * 60 * 60), shift by -180 * 60 * 60 and split in degrees, minutes and seconds when displaying. -- Ludovic Brenta.
From: Martin on 5 Feb 2010 04:02
On Feb 5, 8:52 am, Ludovic Brenta <ludo...(a)ludovic-brenta.org> wrote: > Martin wrote on comp.lang.ada: > > > > > On Feb 5, 6:42 am, Dennis Lee Bieber <wlfr...(a)ix.netcom.com> wrote: > > > On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...(a)obry.net> > > > declaimed the following in comp.lang.ada: > > > > I know that the F-22 is 90% of Ada. Is there some public information > > > > about this bug? Is that a design bug? > > > > So far as I recall -- from some years ago -- it was an algorithm > > > problem handling position information wrap-around from crossing, as > > > mentioned, the International Dateline... -180.0 to +180.0 deg longitude. > > > > I didn't hear that they had to follow the tankers back -- was under > > > the impression once they managed to cross back heading east a reboot of > > > the navigation system started working again... > > > > -- > > > Wulfraed Dennis Lee Bieber KD6MOG > > > wlfr...(a)ix.netcom.com HTTP://wlfraed.home.netcom.com/ > > > For some reason (that I don't get at all) lots of systems define long > > as -180 <= x <= +180 degrees. > > > Having the potential to alias a position seems like a bad idea for a > > start, so when I've been coding such systems up, I've always spent a > > bit of time making it convert positions into the range -180 <= x < > > +180 degrees and using a proper ADT. > > > I wonder if it was anything to do with that?... > > I would have thought a longitude was really a mod 360, shifted by -180 > for display purposes? For fractional degrees (i.e. minutes and > seconds), make that mod (360 * 60 * 60), shift by -180 * 60 * 60 and > split in degrees, minutes and seconds when displaying. > > -- > Ludovic Brenta. No...it's -180 <= x <(=) +180...always - check any map / globe!! Lat is always -90 <= x <= +90 deg - no doubt about that one :-) Adding "shifts" would make understanding any problem very hard... "So the position coming in is (+40, -100) but what's that inside the code again????" Cheers -- Martin |