|Quoting Mandala499 (Reply 4):|
Sounds like FBW = fulltime CWS with envelope protection doesn't it
Somewhat but not quite.
On an Airbus (except the A300 and A310) when you move the stick, the computers interpret pilot deflection to mean "oh, you want the plane to change direction by x degrees per second in the roll and pitch axes". The computers then move the surfaces to give you that desired change in direction rate (unless said desires are beyond what is allowed by flight envelope protection). This is regardless of outside (the cockpit) factors such as airspeed.
On a Boeing, when you move the yoke (or the stick in a C-17
) pilot deflection is directly reflected in control surface deflection. It has a certain correlation with directional change rate, but this correlation is highly affected by external factors. (Note that there are surface movement limiters. Just like on a car, if you move the wheel/yoke x degrees, this is equivalent to a smaller deflection at higher speed.)
So. On the Airbus you have replaced the human brain compensating for outside factors with automation.
But, and this is a very important point, the Airbus system does not "replace the pilot". The pilot is still very much in charge of what happens. Unless he or she does something stupid like try to break the plane of course. Flight envelope protection can be somewhat compared to stability systems in some modern cars. If you try to drive your four wheel drive Mercedes through a turn on a gravel road too quickly, the stability systems will intervene to ensure you have maximum grip. Until you get to that point ("the point of stupidity"), the Mercedes will let you do what you want. Beyond that point there's s an extra insurance, but it doesn't mean that the plane (or car) will rescue you from really really stupid behavior (A320 Mulhouse crash).
Not to raise a hornet's nest here, but could Airbus flight envelope protection have saved AA587 by preventing rudder movement beyond structural limits? I'll go out on a limb here and say that it would have prevented the fin from snapping off. Whether this would have saved the plane is another matter. But this illustrates my point. It's an extra insurance, but if you do something wrong any plane can bite you in the ass.
One pilot I spoke to recently put it quite well. I paraphrase: "In the military, I was taught to fly to the very edges of the envelope. Here, we try to fly as close to the middle of the envelope as possible." Or in other words: "A good pilot will use his superior skills to keep himself out of situations where he might have to use them." This is true regardless of model.
|Quoting Pihero (Reply 5):|
I'm impressed with your grasp of the A flight controls.
Thx. I guess all the time on A.nut is paying off
[Edited 2005-08-26 16:24:05]