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 Newsgroups: comp.lang.ada Subject: Re: F-22 Raptor software problem References: <1172534147.771342.169000@p10g2000cwp.googlegroups.com> <1172666017.141406.173400@v33g2000cwv.googlegroups.com> From: Markus E Leypold Organization: N/A Date: Wed, 28 Feb 2007 17:15:09 +0100 Message-ID: <2u649mp8c2.fsf@hod.lan.m-e-leypold.de> User-Agent: Some cool user agent (SCUG) Cancel-Lock: sha1:iZmIhQ5E5VJ0Hv/mu8Z9T3Q6iXk= MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii NNTP-Posting-Host: 88.72.230.204 X-Trace: news.arcor-ip.de 1172678953 88.72.230.204 (28 Feb 2007 17:09:13 +0200) X-Complaints-To: abuse@arcor-ip.de Path: g2news2.google.com!news2.google.com!news3.google.com!border1.nntp.dca.giganews.com!border2.nntp.dca.giganews.com!nntp.giganews.com!newspeer1.nwr.nac.net!newsfeed.freenet.de!news.tu-darmstadt.de!newsfeed.hanau.net!newsfeed01.sul.t-online.de!t-online.de!newsfeed.arcor-ip.de!news.arcor-ip.de!not-for-mail Xref: g2news2.google.com comp.lang.ada:9613 Date: 2007-02-28T17:15:09+01:00 List-Id: "Bob Spooner" writes: > "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 On would think that internal time keeping would always done in GMT or with a counter with a fixed offset to GMT, esp. since GPS works with GMT anyway. Regards -- Markus