Newsgroups: sci.aeronautics.airliners Path: news From: rdd@cactus.org (Robert Dorsett) Subject: Re: Flight controls X-Submission-Date: Thu, 10 Dec 92 5:22:58 CST References: <1992Nov26.000453.4729@cactus.org> <1992Dec01.025604.17493@news.mentorg.com> airliners.1992.77@ohare.Chicago.COM> Message-ID: Approved: kls@ohare.Chicago.COM Sender: kls@ohare.Chicago.COM X-Submission-Message-Id: Date: 10 Dec 92 16:07:06 PST In philip@rainbow.mentorg.com (Philip Peake) wrote: > In article , rdd@cactus.org (Robert Dorsett > if you want to knock the A320, there are much better grounds for doing so > than ergonomics - without the more serious design problems, there would probably > have been many fewer "accidents", and hence less reason to blame the ergonomics. I am hard pressed to think of many other things. Structurally, the A320 is extremely conservative, highly conventional. In systems layout and design, highly conventional. There are a few frills, such as the cabin lighting system, toilets, or window heat, which have been "automated," but only in relatively self-contained manners (toilet going out doesn't have the slightest ramification on ELAC 1 being able to do its job, for instance: they aren't on the same networks :-)). The EFCS, in turn, has been the focus of so much attention that at least one pundit suggested that other aspects may have been allowed to lapse, as evidenced by the initial problems with the toilets or the cabin intercom/ lighting system, the latter of which, in the words of a BA maintenance engineer, had software so simple "a child could have done it better." These aren't safety-critical items (well, maybe the lighting is: it didn't work at Habsheim). Two of the three accidents were misuses of the FMGS MCU; the other--the first--was so bizarre, such an outrageous case of poor airmanship, that I've yet to fully assess the implications. This therefore seems to call for better ergonomics or training, with the latter recognized as precisely what it is: a kludge, covering up poor design. It's important to note that while, on a quantifiable basis, the A320's EFCS is most subject to criticism, it's equally clear that, thus far, the EFCS has performed almost flawlessly. And even if it doesn't meet the 1-in-a-billion failure rate, it's likely that if it produces even one EFCS-induced catastrophic failure every 10 years, the human and material costs can be easily absorbed by the industry--and when it does fail, we probably wouldn't be able to determine what happens, since the DFDR certainly doesn't record the myriad execution paths. The real issue, of course, is whether this is as safe as a conventional system. And if it isn't, there are tremendous ethical and moral issues at play. > Besides "cosmetic" issues like tactile feedback, and some layout issues, This isn't cosmetic. The choice of using sidesticks, the four major flight control modes, the many possible permutations within those modes, are part of a highly integrated *system* design. If one looks at it for itself, it's a very "sexy" design, a startingly coherent design philosophy. How well it adapts to the real world is another issue, entirely, of course. I would even suggest that if one disqualifies one aspect of this model: sidestick, throttle control, switch design--the totality could suffer irreparable damage. None of this is "cosmetic." It's the heart of how the airplane is controlled. > the 767 > is pretty close to an A320 - as you have said (I think - sorry if I misquote > you) > the 767 is just more conventional in cockpit design - its a pity its automatic > landing system can be as good as the best pilot on a good day, and a rough as > the worst on a bad day ... usually more towards the latter ... I would not have rated the airplanes as equivalents. The 767 is "equivalent" to an A310, but even then, there are significant differences in cockpit design. If I've given the impression of "equivalency," it was by mistake: perhaps in avionics maintenance practices, or the A320 or 747-400 as "consumers" of the benefits of the 767/A310 learning curve; little else. The airplane I'd compare with the A320 is the 747-400, at least in cockpit design, systems design, and AIDS/BITE integration; certainly not the mission requirements. > ) writes: > |> We can automate easily quantifiable issues: simple tasks. Judgement and > |> airmanship has thus far evaded us, on all levels. Until we get a grip on > |> it, talk of fully autonomous aircraft or ground control is nothing more > |> than science fiction. > > [...] history, even modern history is littered with comments from > people writing off things as "science fiction", "can't be done", "will never rep > lace > the current ...." etc who have had to eat their words shortly after. In the software engineering community, words like "Oh, that's easy," or "I can do that on time, on schedule, and under budget" are *always* eaten, later on. Software is an art, not an engineering discipline. I wonder what the aero manufacturers are doing that the rest of us poor sods aren't, that let them miraculously produce highly complex packages right on schedule, in a certification environment in which even a day's delay can costs millions of dollars. 10M of code in an A330/340, indeed. I have a hard enough time keeping my little 1M Microsoft Word in line. Usually, when I write "stupid" things, I regret it an hour later. It's been over 72 hours, now, and I stand by my words. At this point in time, it is not feasible to create fully autonomous transport aircraft, as implied in the original article. By the time it is, I expect my bones to be dust. Incidentally, a few people seem to have interpreted my comments about software engineering as coming from an AE perspective: they weren't. I'm not sanguine about CS types writing this stuff: I simply don't think development technology's at a point where we can write reliable software with the level of confidence I feel is necessary. This is a whole other discussion, though. I actually have little experience with the capabilities of AE-types to write code. Although I suppose if they had done it, the EFCS would have been written in FORTRAN, not C/Pascal/assembly. :-) I will concede that the CS approach is likely the lesser of two evils. --- Robert Dorsett rdd@cactus.org ...cs.utexas.edu!cactus.org!rdd