747 autopilot questions

[digant]

I have some questions about using autopilot on a 747 (and other planes, really).

First of all, can someone explain to me the difference between the various buttons: Heading, Nav, Back Course, Approach (I usually fly using the Heading Hold and Alt Hold but I am curious how Nav is different than Heading Hold, and what Back Course and Approach are).

Second, is there a step by step guide to using the Approach?  I know I have to use the ILS freq on Nav1 of the radio but from that point, I'm not sure how the APP works.  I have used it once and it seemed to line me up on the runway and I controlled the speed and pitch to come down for a landing.  But the next time I used it, the autopilot insisted on flying my airplane towards the ground straight into downtown Dallas (coming in to KDAL).  What all does Approach handle for me and how do I use it properly?

[Nexus]

This is gonna be quick (I'm at work)
Heading hold (a.k.a Heading select) will keep the aircraft at the selected heading, however it won

[garymbuska]

I strongly suggest you take some of the lessons in FS2004 They should help you a lot. The checkrides at the end may not work right. But after flying them a couple of times you should be able to judge for yourself if you are ready for the next step. Just take your time and in the end you will master it.

[MadDriver]

For NAV... do you put the VOR frequency in NAV 1 and activate it?  

[Nexus]

Yeah, since you're flying in the captain's seat, you'd use NAV 1 radio along with the course selector.
The first officer will obviously use NAV 2