I raised this with the A2A tech forum but the problems seems to be more Reality XP related so here goes: I'm Running A2A Piper 180 on P3Dv5 with all 

When on RNAV / Vectors to Final the GNS tracks the AP like it is on rails.. I landed twice absolutely fine. No issue. 

However.. when I try and follow an active leg of a flight plan, the plane wanders off course like a drunk walking home on a country road. Doesn't matter how close to the line, how straight to the line.. dam thing just slowly meanders off course. I'm using the same settings for approach.. not a problem.. But plotting a flight plan heading, It seems to think about it when I turn on HI trk, turn a bit towards the mark and then just stay there.. not correcting.

Help!

Hi,

I'd first tend to think this is most likely is an issue with the aircraft autopilot custom coding.

Here is why: the GNS is interfacing at a very low level in the simulator A/P system (hence why we have to make a new update to the product every time there is a new P3D version). There is nothing different in this interfacing whether it is on approach or enroute. The precision is the same etc...

However, if the aircraft autopilot has been custom coded to simulate, for example, a 'tight' tracking for ILS and 'loose' tracking for VOR, it is possible their code is 'loose' tracking the GNS signal if not in approach. In this case this is wrong. Any such A/P system in the real world also has an input signal which is triggered by the GPS to make it believe it is an ILS class signal with 'tight' tracking. This signal is available from our GNS/GTN and it is up to 3rd party vendors to use it should they implement a 'custom sophisticated' A/P system.

Conversely, if their is no special coding involved in the aircraft A/P system and because the GNS/GTN makes no difference in A/P signal whether enroute or approach, it might be something else related to the parametrization of the A/P constants for this aircraft.

I'm open to any other suggestion though.

 

Edited June 8, 20205 yr by RXP

Have you tried various options in the settings menu? I know, this shows for a GTN, but the GNS Settings are accessed the same way. In some aircraft you may need to click the bezel of the pop up gauge as the aircraft's virtual cockpit bezel may interfere.  The User's Guide explains how to select various settings.  What is needed varies by aircraft as not all aircraft model developers design to the same standard.  That is particularly true when a developer closely models a vintage aircraft with vintage autopilot.  

Also, here is a link to a tutorial for the STEC AP in that model:

https://www.youtube.com/watch?v=-96FkQ8LP50