Originally Posted by RR_NDB post #610
When you have 3, 5, 7, (odd number), etc. critical elements, your System is able to:
1. Compare elements trying to figure out the “truth” i.e. their correct “output”
2. “Vote” to select the best ones (the ones that are probably presenting correct results)
3. Implement a more “fault tolerant” system for a better (safer) System availability
4. Promote a “graceful degradation” in the overall system
But this is only valid for elements with low chances to fail simultaneously. This is well done In Airbus SAS planes with triple critical computing elements (acting as 5). A solid Engineering approach.
A very good discussion which resulted from
BOAC and
Nigel-on-Draft's extended discussion on the Airbus Crash/Training Flight thread in R&N, produced links to several interesting documents on redundancy and voting.
"
Reaching Agreement in the Presence of Faults", (figuring out the 'truth' in complex systems), can be found on that Airbus Crash/Training Flight thread beginning
here. The references are to the
Byzantine General's Problem first posited by
Lamport, (original comments and link provided by
PBL at Post #1297 to which the link above is referenced), and elaborated by
Kevin Driscoll and others in
Byzantine Fault Tolerance; From Theory to Reality provide a lively discussion on the notion of FCPC (and other computers), "voting", and the problems faced, even by crews, (and NOT limited to the Airbus...the Turkish B737 Radio Altimeter problem is such a problem).
BOAC;
I think we agree on your notion of, "continuing the fight".
What I meant by "narrowing...etc" was, I don't think the fight can be carried forward by criticizing this or that aspect or detail of the one design. The B777 is partially automated, and Boeing's B787 is, one day, going to top the Airbus concept in spades. The problem isn't "the Airbus"; the problem is attitudes and denials of what automation is, what it can and cannot accomplish reliably and the biggest principle of all, "who is in control?"
I have consistently offered the view that "
marketing" from the manufacturer and bought into by the customers (airlines) has always led the pathway to automation 'buy-in". Certainly automation does not sell itself through actual comprehension of complex systems and the notion that automation can go wrong is just never discussed in polite sales-and-cocktails circles. Pilots, not MBAs and those informed by and solely driven by finance, knew better but, (and I have many AW&ST articles as well as personal emails from the early 90's discussing "mode confusion" asking how to deal with it), pilots were ignored in favour of cheaper training, common cockpits and the need for lower skill levels in new-hires. Like I said before, George Carlin said it best.
You can see the marketing approach in practically everything Airbus writes or ever wrote. Problem is, while most pilots knew better and just got on with the job of flying an airplane and learning about the new systems and occasoinally providing feedback (which was initially, arrogantly ignored by Airbus), the regulators, airline financial people, the standards, checking and training people and even some pilots took the marketing people at their word. Consequently, here for example in Canada, demonstrating and otherwise teaching/training the approach to the stall is not required for FBW aircraft. THAT is how far the mythology has been entrenched. Now it stands ready to reach those for whom the digitizing and control of flight are an invisible phenomenon and who, as a result, may not have great stick-and-rudder skills or even the raw survival skills so needed to stay alive in an airplane. On this, you and I fully agree.
I constantly support the Airbus aircraft because it is first an airplane, and not because I think or believe that it is a superior concept in solving the problems of flight. I think simpler is better but quite frankly BOAC, we pilots don't drive the industry - finance does, even to the point of throwing dice on occasion. If you want a profound example of a company and a design that truly deserved heavy criticism and I think jail time for that company's management, take a look at "The DC10 Story".
I have also consistently said that the design demands heavy criticism where warranted (and have done so many times), but to be able to do that, and you may not agree, I think one should be trained on the airplane and have some experience with it, because, some of the problems seen by those not on the airplane disappear when one knows and flies the machine.