I was hoping someone has had a similiar problem or can point out what I am doing wrong. I have been unable to get VNAV to work and keep getting the message "VNAV DISCONNECT" on the FMC. I set up everything as far as I know correct in the FMC including Performance Initialization and N1 Limits and get my V speeds correctly. I have ensured that all autopilot setting are correct including V2 entered and crusing altitude and prior to spooling up the engines on takeoff I engage the F/D switch and arm the autothrottle. Once the engines are stabilized at 70% I engage N1 and rollout. I hand fly the a/c to approxmately 400-600 feet and then engage LNAV and VNAV. LNAV engages all the time and VNAV "nada". I am sure I am doing something wrong but can't for the life of me figure out what as I have followed this procedure for every other a/c.Any help would be greatly appreciated.Richard RoweCA342019

Richard,You probably set your cruize alt at a height which will cause TOD to be calculated before TOC... This would be the case if the cruize alt is too high, and the distance needed to descent extends in the flight plan to a point before the top of climb.Try reducing your cruize alt.anthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

disregard

Hey,That just happened to me... I've had a couple of flights where VNAV worked fine, but this latest flight gave me the VNAV DISCONNECT issue. The flight was from Halifax to Ottawa at FL330, so no problem reaching the cruise alt...I'm kind of holding off posting questions until the manual is released (most likely this is pilot error), but if anybody knows off-hand what Richard and I might have accidentally skipped in the setup...Thanks,Greghttp://members.rogers.com/gmoffatt/images/ERJ_CRT.jpg

At the moment, the only thing I can think of is maybe the aircraft cannot reach the set altitude because the aircarft is too heavy. Hauling a fully loaded 737 up to FL330 is tough going.Best,Bill

I've been holding back on the questions for the same reason Greg. But I have the same problem. I've never gotten VNAV to function no matter what the weight or FL. I can do this all day in the "other" 737 and the PIC767 but just can't figure out a way to make it work here. We've got to be missing an input somewhere but I'll be darned if I can find it. I've even gone over the FMC stuff in my 737 Flight Manual and still can't get a clue. Maybe the light bulb will come on when we've seen the manual.Doug

Just thought I would let you know that I flew a flight from CYYZ to CYUL at FL260 and the VNAV worked perfectly. I guess it was the short test flights that were pushing the descent ahead of the top of climb.:-)Regards,Richard RoweCA432019

Mine not only has the VNAV Disconnect, but it lost every waypoint from the end of the SID to the beginning of the STAR :(Wilson HinesUAL006|UPS1008|CX776--------------------------------------Proficiencies: PSS 747,777, A32x, CS 727---------------------------------------ActiveSky|FSRealTime|FSBuild2|FSNav|Jep SimCharts2---------------------------------------Athlon XP 2600+|Thermaltake Volcano 7+|Gigabyte GA-7VXP (rev1.1)|Geil PC3200 512MB|GeFarce Ti4600|Antec 1060 SOHO|WD 120 GB 8MB round cables|Lite-On 48X CDRW|Razer Boomslang|19" NEC FE950 & 19" Sony Trinitron| Saitek X45 throttle and stick|HP Scanner and DeskJet 890C|MS Win XP SP1|http://heavylhc.com/images/av/anna.jpg

I too have experienced this same problem. VNAV worked for me on a flight from PHNL to PHKO. Since then it has never worked (even when I've repeated the exact same flight from PHNL to PHKO). I'm sure its not related to the cruising altitude being too high (because I used FL240 both times I flew from PHNL to PHKO). I'm equally sure I've entered everything I should be into the FMC (unless I was just incredibly lucky the first time I did it). I'm of the opinion this problem is caused by a bug in the software rather than user error but I'd be happy to be proved wrong (because then I could use VNAV again).

I forgot to mention that ever since VNAV stopped working for me I don't get to see TOC/TOD on the navigation display anymore. Presumeably this is why I get the VNAV DISCONNECT message when trying to engage VNAV. The question is, whats happened to the TOC/TOD marks?

Okay, it turns out it was user error after all! I did some more experimentation and found out that if you enter a Cost Index (instead of just leaving it blank) then you will get the TOD/TOC marks on your navigation display and then, lo and behold, you can engage VNAV mode without getting the VNAV DISCONNECTED msg (assuming TOC is also before TOD). Possibly the first time you run the FMC it has a default value in there for the Cost Index because VNAV mode worked for me the first time I used it and I don't remember entering a value for that flight.

Thanks for the clue Craig. Putting a value in the CI fixed it here also. I just assumed because the CI wasn't yet implemented it could be left blank. Another bad guess :-) . Now they need to solve the descent issue (MCP reset doesn't seem to be working properly) and we're all set. Where's the manual.....?Doug