Hi allIm new to the FMC, however, when i set up a flight, i add speed at various heights to waypoints. Problem is, when i press vnav it does nothing, this is the case with pre defined routs as well.Can anyone give a brief overview as the instructions make no sense at all. Can height changes be controlled with Vnav in the 737ng.Many thanksTerry

VNAV controls the programmed vertical flight profile. There are of course many rules and exceptions to this general statement of mine. To be able to engage VNAV one must be within the criteria for the mode. VNAV in descents (if in default PATH) will not keep any speed but only the path with in SPEED it will keep the speed and forsake the path. Take off and make sure the MCP is set either to your clearance altitude or cruise altitude, arm the A/T in CMD (A or :( and engage VNAV. Look at the pilot's flight display for engagement. It's a bit complicated to try to explain all that is involved, this comes from experience and much reading from tutorials..Best Wishes,[h4]Randy J. Smith[/h4]http://www.rawbw.com/~bdoolin/shinault/Animation1.gifCaution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro | Windows Xp Pro 64 |