One of the things to come out of my recent attempts to make gauges in XML is the realization that in spite of using FS since version 1 on the original IBM PC, there are still huge holes in my flying knowledge, which probably explains why I'm a lousy pilot. Please can the experts advise me on the following - (a) When I switch on the autopilot, it appears that the yaw damper and wing leveller also become active, as in this mode the AP continues to fly the aircraft at its current heading and altitude. If I turn on the heading function, the wing leveller turns off, and the aircraft turns to the set heading. From these examples it follows that a single switch change on one autopilot function can trigger off a number of consequent function setting changes. Can anyone give me a list of these inter relationships, or is it not that simple? (b) Does the Flight Director just display the cross-hairs as a guide, or has it more uses? (c) What does the yaw damper do precisely? (d) For a single engined prop panel, under the engine/power heading I plan to include the settings for mixture, throttle, and propellor percentages, plus the rpm and manifold pressure. I assume I can just double this up for a piston engined twin, but what do I need to display for turboprops and jets? (e) What's the difference between autobrakes, spoilers and air brakes? Alternatively, if you can point me to a useful reference site to get the answers, I would be grateful. Many thanks Frank T.