747, Problems with VNAV, LNAV, Autopilot

[Guest feuersteini]

Hello everybody,after many good flights in the PMDG 737 I have bought the PMDG 747 boxed version. But now I have a big problem.After Cockpit-preperation and FMC-preperation (Flightplan with FSNavigator)I make the takeoff with armd VNAV, LNAV, FD on, both AT. I pressed the screw TO/GA. But after aktivate the AP, the plane climb with 4000 ft or more, the speed goes near STALL, after passing the altitude, the plane climbs higher. Pressing the Altitude-Hold-button - no reaktion. The plane takes with aktivate LNAV 180

[Guest dt1951]

If I understand you correctly, you takeoff with the AP's armed. Do not turn on your AP's turned on. Autothrottle and LNAV yes, not Autopilot. Second, unless you are very light, I recommend not arming VNAV right away. Climb out speed is calculated at V2+100, and it is not very often that V2 is 150 kias or less. I sometimes have LNAV armed at takeoff because some airports have very busy SIDS (like the new ones at KATL) where there are waypoints soon after runway departure. I don't turn on the Autopilot until I am stablized after takeoff (somewhere between 500 and 800 ft AGL). Then I can do my vertical navigation by using FL CHG and airpseeds. It give me much better control. You can safely turn on VNAV above 10000'.