I have followed the tutorial on the FMC and created my plan but I can't get Nav to hold the course. When I push nav on the AP nothing happens.Could I be missing something?Any help would be greatly appreciatedThanks in advance

Have you engaged LNAV on the EHSI control panel? Is the autopilot on?If you engage the AP after takeoff you should do so in HDG mode, and when able dial in an intercept course for your route, or use the FMS to do it (using HEADING), or enter a Direct To (D-> key) command to the first waypoint on your flight plan using the FMS.Hope this helps...

Assuming you're talking about the J41, you have to have engaged LNAV on the EHSI when engaging the autopilot vis the center pedestal as Mitchell said. You can also access the autopilot master and yaw damper switched by hitting Shift+3, this also brings up the FMC 2D popup.

Thank you both for the info.

Hi,I engaged the LNAV mode and the autopilot is also ON with HDG selected. But when i push the nav button, the aircraft goes to the north direction even after push the direct to button on the FMS to the next waypoint.Any idea of what's wrong ?ThanksPascal

Sounds like you are making progress. With LNAV pointer on EHSI selected, doesn't it show the bearing to the next fix and the course deviation? Maybe a screen shot would help.

First, thanks for your reply.It seems that I was selecting buttons in bad order. I should have followed tutorial flight instructions closer.After taking off, HDG was selected then inspite of pushing the autopilot button, I was selecting nav mode.So the solution that seems working :1) HDG On with altitude select2) Autopilot on3) Direct to the first waypoint in the FMS4) Finally NAV On with LNAV mode selected.Hope this can help beginners like me.Pascal. (LFPO)