Cessna 172 Autopilot Question

[Mama Symphonia]

Hi there!

I'm trying to follow YouTube tutorials about how to fly an ILS approach using the autopilot in the Cessna 172, but for some reason it doesn't seem to be working the way it's shown in the video.

Here's what I know so far:

- The autopilot switch turns autopilot on. Duh.
- You can get the ILS frequency information from the map (m key) by showing ILS approaches and clicking them.
- There are two functions which control the ILS landing: NAV, which gets you lined up to the runway, and APR, which sets your descent rate once you've intercepted the glideslope. I know that NAV has an additional function that is connected with the switch above the CDI (that can choose between NAV and GPS) but I have no idea how that works.

But when I dial in the ILS frequency, turn autopilot on, turn NAV and APR on, and guide the plane into the glideslope, it seems nothing happens. Actually, sometimes the autopilot will veer the plane off into a seemingly random direction or even crash it into the ground unless I disable the autopilot and take over! The one thing it never seems to do is STAY POINTED AT THE AIRPORT that it's already perfectly lined up with, and it certainly doesn't seem to enter any kind of controlled descent.

Some people told me this is a bug with the XP11 Cessna 172, and that you have to press buttons multiple times in order for them to "catch"... well I've been trying this for a little over three hours and trust me, I've mashed the buttons on the autopilot multiple times. xD

Follow up question, how come airports only have ILS vectors (in the map screen) for SOME of their runways, and not all of them? For example in KTUS, I can get an ILS approach to 11R, but I can't get one if I want to land on the opposite end of the runway. I mean sure I get why it's set up that way in real life, but it feels like an odd restriction for a sim that will let you land in the middle of the desert if you want...

[danny.geom]

The NAV mode on the autopilot can be used to either follow the flight route youve programmed into your FMC if the NAV/GPS switch is set to GPS, or it can be used to intercept VORs or ILS when its on NAV.

If you want to do an ILS approach:
1. Set NAV/GPS switch to NAV
2. Tune in the frequency of the runway you want to land at for NAV1, make sure its the active frequency, not the standby one (very important!)
3. Use HDG select with the AP or fly the plane to the localizer manually
4. Once the CDI comes alive (around 15nm from the airport), press the NAV button (and turn on the Auto Pilot if you havent already). The plane should now fly towards the runway while holding the Altitude.
5. Now pay close attention to the GS indicator. Once that comes alive as well press the APR button, the plane should now start a descent and follow the GS to the runway.

For your follow up question: I can imagine that its quite expensive to install and maintain an ILS system for the airport, so for a regional airport that only gets some commercial flights a day and mostly smaller planes its not necessary to equip every runway with that system.
The sim is supposed to simulate real flying as close as possible, thats why the "restrictions" you might encounter in real life are carried over as well.
Oh, and of course you can land in the middle of the desert in reality as well, im sure people have. Whether those landings were planned or not is probably a different story :)