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=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 109fba,df854b5838c3e14 X-Google-Attributes: gid109fba,public X-Google-Thread: 1014db,df854b5838c3e14 X-Google-Attributes: gid1014db,public X-Google-Thread: 103376,df854b5838c3e14 X-Google-Attributes: gid103376,public From: Ken Garlington Subject: Re: C/C++ knocks the crap out of Ada Date: 1996/02/21 Message-ID: <312B08F0.5DD6@lfwc.lockheed.com>#1/1 X-Deja-AN: 140465477 references: <4etcmm$lpd@nova.dimensional.com> content-type: text/plain; charset=us-ascii organization: Lockheed Martin Tactical Aircraft Systems mime-version: 1.0 newsgroups: comp.lang.ada,comp.lang.c,comp.lang.c++ x-mailer: Mozilla 2.0 (Macintosh; I; 68K) Date: 1996-02-21T00:00:00+00:00 List-Id: Lee Graba wrote: > > > 1. Until relatively recently, the F-16 flight control computer didn't have any > > software in it. It was an analog computer. > > Actually, the F-16A had a hybrid flight control computer. The primary flight > control functions were performed by an analog computer, but some flight control > gains were scheduled with respect to flight condition by a digital computer and > fed to the analog computer. However, setting gains should not cause the above- > described phenomenon. You're right - by analog, I meant that the gains were computed as analog values. The key statement, of course, is that there was no software in it anywhere. The gain scheduling was done via digital non-programmable electronic circuitry. AFTI/F-16 was the first F-16 flight control computer to contain software; it was called the digital flight control computer (and we called the older computer the _analog_ system to distringuish it, even though it did it include digital circuits). The Block 40 system was called the _production_ digital flight control system, BTW. Since all of our newer systems contain software, we now drop the "digital" part and just talk about "the flight control system". > If such a thing did occur, it would probably be due to the Navset, which is > usually a separate digital computer whose responsibility is to take > measurements and then compute positions and attitudes, and associated rates. > A software error here might cause a problem, if say, it was telling the flight > control computer that it was flying straight and level, and suddenly told it > that it was really upside down. The flight control computer would then try > to right the plane, since it doesn't know good information from bad. Well, a single-point Navset failure would be detected, but a generic software fault in an IRS system might not. However, no one has ever been able to say what happened, or even if this ever really did happen (and as such is another software "urban legend" to add to the pile).