Hi,I am having a problem with the VNAV of the 747 PMDG:When I start climbing ,everything's all right. Then, passing about 1000 feet AGL, I try engaging VNAV but it dosen't and engages:FLCHG OR Speed: 100 and VS:(it depends)I keep clicking on VNAV but it just won't let me !!!!!!!I don't understand, the pages of the FMC are complete ! Perf INIT, Thrust LIM, etc...ThanksThibaud

Thibaud,Seems something is amiss in your flight preps even if you think it's all done. Do you have any discontinuities in your route? All boxed entries in the FMC filled out? Care to upload some screenshots of your main screen when this happens?Hope it helps,

Also, Vnav needs a complete route or it will not even arm. You will certainly have a departure point programmed, but also make sure you have an arrival RUNWAY programmed as your destination (ARR/DEP > ARR > select a runway).

"but also make sure you have an arrival RUNWAY programmed as your destination (ARR/DEP > ARR > select a runway)."Arrival runway is not required on the real aircraft... and I've been flying all of my routes in PMDG successfully without doing this, so the problem lies elsewhere. PMDG has a FLCH default mode when your aircraft is about to stall. Ensure that your current airspeed is healthy. VNAV is designed to be armed on the ground (but can be engaged above 400' after takeoff). Try arming it on the ground, to see if it will arm (VNAV should appear in white letters below the green T/O annunciation on your PFD).Cheers.Q>