Originally Posted by
RR_NDB
To say you what happens to me when i realize the "circuitry" amount and complexity used (required) in highly complex FBW a/c.
The complexity is mitigated by redundancy, as you state - and the components themselves (derived from the 80186) were obsolete in computing terms in the late '80s, but highly predictable and easy to understand at a circuit level. To compare that to the incredibly dense multi-pipelined designs used in consumer level computers even 10 years ago is like comparing a trusty old pick-up truck engine (powerful enough to do the job, but reliable over long periods of time) to that of a Formula 1 racer (Immensely powerful, but prone to frequent failure).
Just a detail: You need to use 3X (acting as 5X) redundancy. Approaching the one used in the STS fleet now retiring.
They used 68000s in some of those STS systems. Again - relatively obsolete technology, but comparatively simple and predictable.
I agree 100%. And will use this to ask: Whatīs your feeling (on this issue) on the Revolution (rdware and Software/algorithms[/]) EA introduced using DFBW technology (for the first time in non military planes)? With itīs big implications. Why US didnīt introduce "in parallel"? But this is for another post or even another thread.
I think it was as valid a direction to take when designing the next generation of airliners as any - especially given the accidents that happened in the '70s and '80s with mechanical/hydraulic systems failing due to damage. I studied Software Engineering under Peter Mellor, who you'll see in the Risks archives occasionally, especially relating to the A320 - and what I learned was that the process that they went through designing the systems was utterly exhaustive. Whatever the naysayers profess when it comes to "Keeping it simple", the fact is that the hydraulic systems required for widebody airliners and the artificial feel required to make such controls make sense to a pilot are anything but simple.
DFBW was proven in military terms for a decade before the A320 started carrying passengers, and I think that was a more than reasonable lead time. The US did not openly develop FBW airliners in tandem, but the B777 followed hot on the heels of the A320 - as such I suspect that something similar was on the drawing board as the A320 progressed from the testing phase to production and service. The only difference between the latest generation of Boeing aircraft and that of Airbus is that Airbus developed a new control philosophy based around the new systems, whereas Boeing had their FBW systems drive a facsimile of a "traditional" flight deck environment. The "ain't Boeing, ain't going" crowd like to say that they don't trust computers in charge of their aircraft, but the B777 (and presumably the B787) is as reliant on it's computers as any Airbus FBW model.