I am not able to arm the V NAV mode before takeoff.Can anyone suggest a solution ? Everything on the MCP including L NAV is working perfect.Appreciate your prompt assistanceThank youKrisana

when you go to arm VNAV does any error message show up in the FMC?

Make sure all entries in the FMC, on the takeoff page, are in large font.CheersSteve

yes, there is an error which says " Unable next alt "Route from EGLL to EDDF .Runway 09LMy frist way point in the LEG page was DVR which I had enter the speed/ altitude restiction as 200/3000.I don't remember other way points.Then I assigned 3000 on ALT Window of the MCP.At the take off point I could arm the L NAV mode but could not do for V NAV.It simply wouldn't work at all.I got the message in the FMC as " Unable next alt "Thanks for the help !

I think the takeoff page of the FMC deals with the flap setting ,and the condition of the runway ..wet or dry.All the entries were in large fonts and I could get the values for the V1 ,Vr and V2.Thanks !

I have had a similiar experience.. once airborne it usually clears.

Are you able to solve this problem while still on ground.Or you still prefer to ignore this by activating V NAV when airborne ?Something must be wrong somewhere.Earlier I used to fly on AEROWINX'S Precision Simulator but had never experienced this kind of problem.

Your airplane is telling you she cannot make the climb as you have requested.

Krisana I just tried this and VNAV armed fine. I am not sure why you would want to cross waypoint DVR at 200 kts and 3000ft. The waypoint is 72 miles away! Unless of course you are wantinmg to check out the scenery!. Are you sure you didnt have 30,000 ft there? That would bring up the "unable next alt" message. Maybe some screen shots including one of your VNAV TO page and one of the legs page would help. Make sure that the ND is enlarged and not obscured by the FMC. CheersSteve

Dear Steve and those who are kind enough to assistIt was a mistake on my part.The message I got on the FMC actually was " UNABLE CRZ ALT ".The V NAV mode could not be armed though !Anyway,Please note down some of the details I made on the new flight set up this afternoon.The result was the same ie The V NAV mode could not be armed and there was a message on the leg page.." UNABLE CRZ ALT "Ok here it goesFlight from EGLL to EDDFRWY 27 L selected from the ARR / DEP page with SID DET 2 G The leg segment of the FMC had the following waypointsDET 250 / 6000KONAN 280 / 12000KOK 280 / 16000LARED 300 / 30000NTM 300 / 30000ADENU 300 / 30000PIMUS 280 / 25000FFM 250 / 6000The CRZ Altitude in the V NAV page was set at 30000In the PERF PageGR Wt 383.7Fuel 172.0 calZFW 211.7RSV the value could not be entered " invalid entry "Cost Index =100 In the THR Limit pageOAT 15 CTO N1 = 104.4 % with TO1 ( SEL ) and CLB ( ARM )In the Take off pageFlpas 20 / 1000 FE/ O Acc Ht 800 Ftrunway DryV1 152Vr 168V2 179All the figures were in big fontsI then set the IAS on the MCP window as 179 and set the ALT window of the MCP as 6000 corresponding to the altitude over the first waypoint DVR.I then switched on the F/D and the the A/T swithes.L NAV could be armed but V NAV could not be armed.There was a message in the FMC which said..." UNABLE CRZ ALT "Steve this is what happened this afternoon and unfortunately I could not also unzip the TRC lessons 2 ,3 and 4.God knows why !!Could you please prepare a route for me from EGLL to EDDF with all the proper setup of the FMC so that i could in the mean time learn from your note and find out where my mistakes lie.Best,Krisana

Krisana did you enter those speed and alts against the waypoints? If you did try again without entering them and see what happens. I do not normally enter any descent information until I am well into the cruise.See if that helps first of all and then we can take it from there.CheersSteve

Hi Steve,This time I decided to use the routing provided by PMDG.I flew from Bangkok to Calcutta in India using the company route BKKCCU001.Everything worked fine and I could armed the L NAV and V NAV modes.I will take some more flights using the given routes before planning them on my own. Last night I spent quite a good time reading through the mannual and have learnt a lot.I have had a hand for almost a year with Aerowinx's Boeing 747 400 so reading through the mannual last night was fun and easy to understand.However I did experienced 2 problems this afternoon and I am going to put it in a new heading.Please read them !Thanks / Kris