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Old 27th Jan 2012, 22:59
  #1547 (permalink)  
ChristiaanJ
 
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Originally Posted by CliveL
One for Christiaan I think
Sorry all, this is now forty years back, literally....
So no, I don't have all the block diagrams and circuit diagrams in my head any more... I'll have to look through what I still have in the way of documentation.
i'll try to give some quick answers.

Da-20 monkey,
Yes, Concorde had "artifcial damping", or "autostabilsation" as we called it, on all three axes (pitch, roll and yaw), even if it could be flown without it.
On the prototypes there were three separate computers (one per axis).
On the preprod and production aircraft the A/S function was 'compressed' into a single unit (I still have one).

CliveL has given the basic answer.
Don't confuse the Concorde FBW (which we referred to as "electrical signalling") with the current "Airbus" digital FBW.

One, rather than in previous-generation aircraft, the pilot no longer pushed and pulled on cables and rods to move the control surfaces. Instead, when he moved the controls, those movements were translated into electrical signals that were sent to the electro-hydraulic control surface actuators (even if in the Concorde days there still was a mechanical back-up).

Two, the entire system was "analogue". A concept difficult to explain in these days, where nearly everything is digital.....
Very briefly, you can convert 'physical' data, like control positions, or altitude, or pitch or roll rate, or Mach number, into 'analogue' electrical signals. You can then perform all kinds of 'computations' on those signals, like filtering them, or add or subtract them, or even multiply them, using electronic circuits based on 'operational amplifiers'.

In digital systems you go one step further.... you convert all those data into digital values, and use a digital computer to perform all your calculations, in accordance with the 'system software', then convert all the results back into physical data, such as control surface commands.

In analogue systems there is no "software". The entire system is defined by 'control laws ' (not the same thing at all as in the Airbus FBW aircraft) that are fixed in terms of 'transfer functions' of the various control loops.
Those in turn are determined by the values of the components in the various electronic circuits (resistors and capacitors mostly). So in those golden days.... we didn't re-write and re-program software.... we changed resistor and capacitors, and re-wired logic circuits.

I admit, you almost have to have been there to understand it....

I'm not sure whether it's worth starting an entire new thread on 'analogue computing' (maybe there's something on wikipedia, I haven't looked)....

CJ
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