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joherszch

Getting both LNAV and VNAV disconnect ;)

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Hi, when I load a route into the FMC, and put all the important things into it. And then when I on climb engage the A/P and push the LNAV and VNAV buttons, I get FMC First message right above the HSI. I open the FMC and get NOT ON INTERCEPT HEADING and VNAV DISCONNECT UNABLE CRZ ALT messages. Well, I must be doing something really wrong :D Because I tried 5 diffrent flightplans. CheersJohan Adolfsson

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>Hi, when I load a route into the FMC, and put all the>important things into it. And then when I on climb engage the>A/P and push the LNAV and VNAV buttons, I get FMC First>message right above the HSI. I open the FMC and get NOT ON>INTERCEPT HEADING and VNAV DISCONNECT UNABLE CRZ ALT messages.>Well, I must be doing something really wrong :D Because I>tried 5 diffrent flightplans. >>Cheers>>Johan AdolfssonLNAV Engagement: You must be within 3 nm of the route, and on *any* heading, and the LNAV mode will enage and will roll the plane to the correct heading to follow the route.Or...If you are more than 3 nm from the route, your intercept heading must be < 90* and intercept the route before the active waypoint. If you fail to meet those standards, you will get the scratchpad message not on intercept heading.About the VNAV message, I think that means your T/D (top of descent) is before the point at which you will reach cruse. To fix, fly a longer route, or pick a lower cruise alt.

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Hello! UNABLE CRZ ALTITUDE FMC predicts aircraft cannot reach the new CRZ ALT due to performance limitations or no cruise time possible as entered CRZ ALTSOULUTION Clear the message and review CRZ ALT selection. Enter aircraft altitude or lower. FMC will not recognize descent phase untill cruise phase is attained. So, select a lower crz altitude for this particular route...[h4]Best Wishes,Randy J. Smithhttp://www.precisionmanuals.com/images/betaimg.jpg

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Lower crz alt for this route? are you kidding?. It's a flight from Stockholm, Sweden to Heathrow, London. In the real world, a 737NG vil cruise at a much higher FL than 320. Even in Norway we have NG's that flies at FL 410 on domestic flights (flight between souther norway and Northern Norway)Jan Roar R

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Hi, did a quick test but I get the same message. I tried both to enter a lower and a higher altitude. But still it disconnects! Am I the only one this problem?CheersJohan Adolfsson

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are you entering the INIT page correctly ... zfw ... etc ...try maybe to not go on a full loaded plane.FL410 is reached when the airplane do not have so much weight and passengers onboard.Load the loadmanager and other option, go to FS9 and change weight settings.I dont know if thats the problem you have, You should with full loaded plane go to about FL350 Can you in short wright what you do in FMC

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This flight is 231 miles. Now you are asking the bird to get up to a crz alt and have time for a descnt all within this space-time. What IS possible here? I'm sure all the performance folks can chime in ;). Here is what a little real 737 trainer shows for this exact route and what happens when I enter FL350. ROUTE ESGG-ESSA shows this message. I do not know if Nutcase was refering to this route but there is simply no way to get that high in this amount of miles.http://forums.avsim.net/user_files/53389.jpg So, the FMC is telling you at ECON CLIMB you aren't gonna make it ;) TRY selecting MAX CLIMB for FL270 and see if it will take it. Realisticly it looks like FL240 ish will be fine. The whole idea here is to work with the FMS and not ask it to completly do all the work needed. Sometimes we need to adjust various things to make it work the way WE want it too, but this does not mean that it will always let us! [h4]Best Wishes,Randy J. Smithhttp://www.precisionmanuals.com/images/betaimg.jpg

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hey Johan!I'm sorry if im teaching you to suck eggs, but you are remembering to set your cruise altitude in the Altitude box of your MCP (autopilot) arn't you?That was the problem I had when I converted from airbuses - i didn't know you had to stick the altitude in the autopilot and it wasn't until fred brought out his tutorial that I found out!Sorry again ;)Liam

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I have tested with altitudes from FL150 to FL325 for that flight :D I never thought this was going to be this difficult!CheersJohan Adolfsson

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>I have tested with altitudes from FL150 to FL325 for that>flight :D I never thought this was going to be this>difficult!Johan,Do you get this error on a longer route, say KJFK-KORD?

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Are you using the -600 or -700?Because I see you are heavy but have a trim ccalculated at 4.50....that sounds like a -600 to me.But if it is a -600 then you are overweight...max GW is 144.000 lbs...so maybe tha's the problem, infact as you see the FMC hasn't calculated the TRIP FL...you only have the CRZ FL input by you.So this might be the issue. Hope this helps. :-)Regards,Bjorn

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I don't miss that Liam! Unfortunately one might say. I have tried all kinds of routes. Since I fly mostly in Europe the longest flight I have prepared is ESSA-LIRF. That should be enough for the plane to reach FL325 right? :D I have uninstall and install the plane twice. Same problem appears! This is really odd, everyone that have talked with haven't had any problems with this.......And last, Bjorn I flew the -700 on that route. Even if they mostly fly -700 in Norway.CheersJohan "Whats VNAV?!?!" Adolfsson

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>Johan "Whats VNAV?!?!" AdolfssonSorry that I can't help more, but I had a small chuckle at that :)

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Happy to hear that :) I am going to do some more testing and see if I can find anything else!CheersJohan Adolfsson

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This is probably a pointless comment, however, under the a/c perf init page you have entered T/C OAT = +14C. First off, correct me if I'm wrong but does T/C mean top of Climb? If it does than you have about +61 degree temp deviation from standard inputed into the FMC. This brings me to my next question which I'll be surprised if the answer is yes, does the flight model for this FMS factor in that temperature entry for performance calculations? If it does than I would bet a jet would be hard pressed to climb at that weight and temp to that altitude. Mark Wisted

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So it does compute that? I'm even more impressed than I was already!Mark wisted

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No comments are pointless :D Thanks for the info! Going to test and set a diffrent temp!CheersJohan "Whats VNAV?!?!" Adolfsson

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Well I guess my main question to that whole comment was whether this FMS actually factors in temperature when it calculates its performance? I am off to the simulator to try it also. Cheers,Mark

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