From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: 103376,d4801f5d6baa249d X-Google-Attributes: gid103376,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news1.google.com!news4.google.com!news.glorb.com!news.aset.psu.edu!not-for-mail From: "Bob Spooner" Newsgroups: comp.lang.ada Subject: Re: F-22 Raptor software problem Date: Wed, 28 Feb 2007 10:51:57 -0500 Organization: Penn State University, Center for Academic Computing Message-ID: References: <1172534147.771342.169000@p10g2000cwp.googlegroups.com> <1172666017.141406.173400@v33g2000cwv.googlegroups.com> NNTP-Posting-Host: nat3.arl.psu.edu X-Trace: f04n12.cac.psu.edu 1172677917 37784 128.118.40.78 (28 Feb 2007 15:51:57 GMT) X-Complaints-To: usenet@f04n12.cac.psu.edu NNTP-Posting-Date: Wed, 28 Feb 2007 15:51:57 +0000 (UTC) X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2900.3028 X-RFC2646: Format=Flowed; Original X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 Xref: g2news2.google.com comp.lang.ada:9601 Date: 2007-02-28T10:51:57-05:00 List-Id: "peter koch" wrote in message news:1172666017.141406.173400@v33g2000cwv.googlegroups.com... > On Feb 28, 8:44 am, Keith Thompson wrote: >> "peter koch" writes: >> > On 26 Feb., 05:47, Hyman Rosen 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