Originally Posted by captjns
Flight Directors are nothing more than a guide to get you going in the correct direction. My students are tought this with the addition of looking beyond the FDs at times as they may provide inaccurate cues at times.
Agree, with one exception and that is the FDs on the Airbus 320/330/340/380 series, (I haven't flown the 777 or the A310/300 etc so can't comment).
The FDs on the Airbus tell you what the autoflight system is commanding...what it wants to do with the inputs it is being provided with
if it had control of the airplane.
So in a way, that fact drives the FDs usefulness to two extremes, from 'very useful' on one end to dangerous on the other.
If one knows one's aircraft well and has been taught well, one would understand that the Airbus FDs can make one aware of what the autoflight would do with the airplane if you weren't hand-flying. (
ed. Thus, the FDs will always be "centered", because the airplane is doing what the autoflight is commanding. QED) You can then make the decision to (re-)engage the AP or ignore (look through) what the FDs are conveying, as you wish.
The other extreme, the dangerous one occurs if doesn't know one's aircraft, in particular the A320/A330 series, and so treats these particular FDs like all previous airplanes, following their commands without understanding, as if the automation "knew" what it was doing in all circumstances. GIGO.
Like any computer, it has no "reason" for doing something - it doesn't "know" why it is doing something because the design is "hard-wired", but we are not.
What has been stated on this thread is completely true in my experience and my opinion -
Centaurus' post is worth reading well. I think it is important to know when to look through the FDs and when the FDs are saying something important. Airbus recognizes this by stating that if you don't intend to follow the FDs, turn them both off.
PJ2