Hey Guys,Posting this question for a friend who just got the 737NG and the 800/900 Pack.For some reason his VNAV button will not arm on the ground. At first i thought he was doing something wrong, so i tried it myself only to end up with the same result. Only solution is to ARM it once airborne(fixes the issue).FMC is all set up correctly and the plane behaves normally during the entire flight.Unlike VNAV, the LNAV button does ARM and illuminate.Leo Calzoni

Nothing abnormal there.Unlike in the 744, VNAV does not arm on the ground in the NG !

Hi Jose Luis ,in the NG , yes we can arm VNAV and LNAV on the ground . :)FO Jouvarn GultomMAS

Hi Jose Luis ,in the NG , yes we can arm VNAV and LNAV on the ground . :)FO Jouvarn GultomMAS

Well, I was referring to the PMDG-NG of course :( Now, could you be more explicit when you say "we" ?Who are "you" then ?Thanks.

Who are "you" then ?

I think his signature is fairly explicit - he is (or he claims to be) first officer with Malaysian Airline.

Search b737.org.uk for vnav arm and you'll find some interesting policies. This is a real world independent pilot resource site.http://www.b737.org.uk/Ibarton73745notes.htm is for a 737 classic but I wonder if the same vnav restriction applies.The other consideration is not to confuse ARM with activation. I don't think the CMD can be enabled until off the ground, usually 500 feet or more AGL by airline policy.Frequently noise abatement areas require a vertical profile not in best economy performance interests and manual attitude and throttle control may be required for the first stage of departure or at least preset MCP controls for speed and V/S.

hmmmmindeed i cant arm CMD on the ground . only VNAV and LNAV . (its a non standard procedure anyway)it worksbut thres seems some slight delay on the thrust reduction during climb . about 100-200feet above the entered thrust reduction AGL in the FMC..as for the classic .. ive never tried it tho :( .and Jose , yeap i am as wat my signature stated . ive already changed it to my name . Jouvarn Gultom

hmmmmindeed i cant arm CMD on the ground . only VNAV and LNAV . (its a non standard procedure anyway)it worksbut thres seems some slight delay on the thrust reduction during climb . about 100-200feet above the entered thrust reduction AGL in the FMC..as for the classic .. ive never tried it tho :( .and Jose , yeap i am as wat my signature stated . ive already changed it to my name . Jouvarn Gultom

From the manual: 09 AFDS System 9-13VNAV mode will not engage (but will arm) if the FMC Performance Initialization page is incomplete.VNAV mode is disengaged by any of the following: Engaging TO/GA, LVL CHG, SPD, V/S, ALT, or G/S pitch modes. Or if VNAV switch is pushed a second time before VNAV engagement.LNAV will engage as long as the aircraft is above 50 AGL and within 2.5 miles of the planned track. If the aircraft is outside of these parameters, LNAV mode will arm and engage when the aircraft moves within these parameters (e.g.- after takeoff).

thanks george ^^tat makes it more clearer.