PPRuNe Forums - View Single Post - Airbus trepidation... convince me otherwise!
Old 22nd May 2012, 21:27
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DozyWannabe
 
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The trick with understanding the FBW Airbus is to realise that the test pilots and engineers who designed it elected to come at airliner operations from the standpoint of the technology available in the early '80s. If something you expect to be there isn't, it's because it's done in a slightly different way.

The reason the sticks aren't interconnected was because they simplified the hardware aspect of the flight deck design. In normal operation only one pilot is supposed to be in control at any given time. Because the controls are fully-hydraulic, the need to use more muscle power on the stick/yoke is not there. The upshot of this is that if your colleague in the other seat suffers an incapacitation, you can take and hold control with the override button and don't need to physically move them until the situation is resolved. This means that when monitoring, you are monitoring the instruments rather than control deflection - but most of those I've spoken to have got fairly used to this.

The same goes for the thrust levers. The actual thrust setting is visually displayed on-screen rather than by physical position - this also can take some getting used to, but most have had little to no difficulty adjusting.

Autotrim is not to be feared - it's simply a logical follow-on from the design of the rest of the system. Either you or the automatics command a pitch angle and the aircraft will trim itself to match. What needs to be borne in mind when discussing AF447 is that the autotrim responded to the PF holding full back stick for almost a minute during a time when the protections were unavailable - the question that everyone's trying to answer is why he did that.

The bank angle and alpha protections only kick in at the edge of the safe flight envelope - it wouldn't surprise me if you never ever encounter them. Contrary to what you may have heard, none of the protections will cause a positive change in attitude opposite that which the pilot orders - the only positive command to come from the protections is the thrust being set to TOGA in Alpha Floor. Everything else just maintains your order at the safe maximum for the airframe.

Another common misconception about the Airbus FBW flight deck was that it was designed by managers, engineers and us computer geeks without pilots getting a word in. Needless to say, this is complete garbage. The engineering and test pilots who worked on the programme were among the best in the world and nothing got through without their say-so.

The Airbus FMS setup is not actually a massive leap over that fitted to the 757. As such it is very important to keep the concept of automation and the concept of FBW separate and distinct in your head. Going on the evidence, Airbus are no more wedded to the concept of automation than any other manufacturer.

But dont take it from me, take it from 757 captain and rock legend Bruce Dickinson:


Last edited by DozyWannabe; 22nd May 2012 at 21:28.
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