I came across to this info in another forum written down by daveygurm10;
Both of your YAW damper switches are INOP which means they are not working.
Your havent aligned your IRS correctly either which is the cause.You can tell this from the yellow TRK on you nav display. This is how to align properly.
1)First, press ALT and go to PMDG options. Find IRS alignment and change it to instant for this test.
2)load cold and dark - ONCE LOADED TURN YOUR IRS SWITCH TO OFF!! 3)standby BAT AUTO, BATTERY ON, APU START 4)APU will begin to run and click APU ENGINE BLEED ON -WAIT 30 SECS OR SO AND THEN YOU CAN CLICK APU AVAIL LIGHTS BY THE APU SWITCH. 5)This is the important bit - IRS - ONE Right Click L,C & R IRS from OFF to NAV and then go straight back to L and LEFT click back to ALIGN, do this for C and R too. 6)Open FMC - Wait for the MSG saying POS INIT or similar. 7)go to POS page and where it says GPS position CLICK THIS and enter the digits intot he boxed filed below. 8)go back to overhead panel and RIGHT CLICK L,C,R IRS back to NAV. all you displys should become alive.
