Something is definitely wrong there. I created a route from YMML to YSSY using PFPX, saved it as a default P3Dv4 .PLN file (YMMLYSSY-PFPX.PLN). I included a SID and STAR. After takeoff, once I switched on the HDG (which was set to the runway heading at the time), then rotated the NAV Source Selector Knob to FMS, it tracked the route no like it should.

I have tested the L-1011 II with the FD Switches set to ON (just one of them, then both), and that worked fine. I also tested with the FD Switches set to SYNC (just one of them, then both), and again that worked fine. As I said in my previous post I normally set both of the FD Switches to SYNC, but since the

I am currently doing a flight, and again I've tested with either one, or both, in the ON position, or the SYNC position, and they are working like they should.

The only reason I can think of why it isn't working for you, is that the MODE SELECTOR Knob on the INS is either not set to NAV, or it was not set to NAV before it was aligned. :-/

EDIT: Reading the manual, I found something else that might be a problem. The AUTO/MAN Switch. I always have this set to AUTO, not MAN.

The manual's description:

14. AUTO/MAN Switch

Selects automatic leg switching by INS (AUTO) or manual leg switching bythe pilot (MAN).

Maybe you have it on MAN?