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,FREEMAIL_FROM autolearn=unavailable autolearn_force=no version=3.4.4 X-Received: by 10.42.12.208 with SMTP id z16mr43504453icz.18.1430704544464; Sun, 03 May 2015 18:55:44 -0700 (PDT) X-Received: by 10.50.114.8 with SMTP id jc8mr109783igb.11.1430704544452; Sun, 03 May 2015 18:55:44 -0700 (PDT) Path: border1.nntp.dca1.giganews.com!nntp.giganews.com!m20no8185999iga.0!news-out.google.com!n7ni24247igk.0!nntp.google.com!l13no13506580iga.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail Newsgroups: comp.lang.ada Date: Sun, 3 May 2015 18:55:43 -0700 (PDT) In-Reply-To: Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=123.2.70.40; posting-account=S_MdrwoAAAD7T2pxG2e393dk6y0tc0Le NNTP-Posting-Host: 123.2.70.40 References: <201505021834588468-rblove@airmailnet> <9f20f713-d65c-471d-ab7c-d314a14fdcd0@googlegroups.com> <1vbdka5a8rqlm8vimai2egm5v1m133pobg@4ax.com> User-Agent: G2/1.0 MIME-Version: 1.0 Message-ID: Subject: Re: Boeing 787 integer overflow From: robin.vowels@gmail.com Injection-Date: Mon, 04 May 2015 01:55:44 +0000 Content-Type: text/plain; charset=ISO-8859-1 Xref: number.nntp.giganews.com comp.lang.ada:193024 Date: 2015-05-03T18:55:43-07:00 List-Id: On Monday, May 4, 2015 at 10:38:45 AM UTC+10, Jeffrey R. Carter wrote: > On 05/03/2015 04:34 PM, Dennis Lee Bieber wrote: > > On Sun, 3 May 2015 12:03:51 -0400, Peter Chapin > > declaimed the following: > > > >> I guess it depends on if there is a *requirement* to reboot the system > >> periodically (less than 8 months) in the maintenance plan. The matter > >> should be handled somewhere and it seems like it wasn't. In other words it > >> was just "luck" that these systems have been getting restarted frequently > >> enough. > > Apparently there isn't, since the AD is to restart the GCUs more frequently. > > > Also depends upon just what "reboot" means in this environment... If > > this is some sort of elapsed time counter, then it is something saved in > > flash memory and will survive a normal power-cycle operation. > > > > "Reboot" in this case may mean erasing and reloading the operational > > flight program, databases, and other stuff in "permanent" memory. > > Since the Ad is to restart the GCUs more frequently, it doesn't appear to be > that complicated. It also says that the effect of the overflow is for the S/W to > go into a special mode, That's failsafe mode. > so it's clear the S/W detects the overflow somehow. Indeed, but the overflow handler was a general one for all overflows in the software. A specific one for that particular timer is clearly needed. I can't imagine why they'd want to shut everything down when there's clearly an error. In a plane, you'd want to continue, if possible, and obviously, this one is continuable. In fact, it's essential that it continue. Sounds like a repeat of the Ariadne failure, where they trapped an interrupt and shut down (placing an error code on the data bus, which data was then interpreted as a direction (attitude) change.