First of all, sorry if this is in the wrong area.I have been using FS for a while (Since about 2004), and two things have always been a mystery to me. First of all, what is the function of the FMC on large airliners, and what does it actually do in flight? Does it operate somehow in conjunction with the autopilot, and steer the aircraft from waypoint to waypoint? If this is the case, I would imagine that I could not use default FSX ATC and file a flight plan with them, as they would be yelling at me to stay on my assigned heading. The other thing is ILS/Auto-land. I have watched and read tutorial after tutorial, and for the life of me I cant get it right@ Is there any fool-proof method of auto-landing an aircraft. Now that I think of it, how does Auto-land work in conjunction with the FMC, if at all? Thanks for any help regarding this matter. hamoody

First up, you'll generally only find a working FMC on payware FS models. The default ones don't have them, at least not in FS9 (and I think FSX), nor does most freeware (see the vasFMC Airbuses for an exception).The clue is in the name. An FMC manages the flight, so the crew don't have to... functions vary from one a/c type to another but would normally include creating and amending flight plans, managing the aircraft's performance (eg calculating and in some cases applying optimal climb rates, cruise speeds, flight levels and so on) and, in flight, monitoring the aircraft's progress and either providing cues to the pilot (if under manual control) or, more commonly, the autopilot, to keep the aircraft on track (LNAV, or laternal navigation mode) and on climb / descent profile (VNAV, or vertical navigation mode). NB that the autopilot / autothrottle manipulates the aircraft controls; the FMC tells it how and when to do so.The human skill comes in programming and interpreting the FMC, both before and during flight. This can be relatively straightforward (say on an Embraer 145 or Dash-8) or fearsomely complex (on the larger Boengs and Airbuses) - again depending on the functionality of the FMC. But (in FS) there is nothing much to stop you using the default ATC. If you program the FMC with an active FS flightplan, or at least one which has the same waypoints as the active FS flightplan, then the two match each other and you don't get yelled at. Some things like step climbs (which default ATC doesn't support) need a bit of creative working around but it can be done. Auto-land is different - it's a combination of autopilot and autothrottle controls which manage the descent and the landing flare to land the aircraft at the right speed and more or less at the touchdown point; in some cases they also slow the aircraft to runway turnoff speed. Doesn't necessarily need an FMC - most just need a working ILS, with the aircraft either locked on to localiser / glideslope or closing on both before autoland is engaged. Indeed auto-land has been around for at least 50 years; FMCs for around half that (the 767 was the first commercial a/c to have one). Again, auto-land isn't widely modelled on non-payware AFAIK though: the Project Fokker F70 and F100 are two exceptions that spring to mind. So if you try it on another type - well it's a bit like one of those mythical pilot reports to maintenance:Pilot report: Auto-land fails to maintain glideslope on short final; touchdown very rough.Engineering response: Auto-land not installed on this aircraft.Hope this makes sense.Tim