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Vnav and Lnav

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When I file a flight plan and I take off, the aircraft will just fly away(autopilot engaged) from the navigation route and the vnav will not engage, and when I click on the Lnav it will fly some other heading and still getting away from navigation course, What am i doing wrong here?

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Guest Dan_Pergau

RTFM - From the convention (supported by 3 or more PIC users).and/orProvide more details of your problems.

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RTFM? well I set the flight from schiphol(EHAM) to New york(KJFK) in the FMC and I took off runway 6 then engaged autopilot, the aircraft was climbing just fine with 250 engaged airpeed, but when i clicked the vnav button it wouldn't activate, however the lnav would activate but the plane was heading north and it wouldn't turn left torwards NY and follow its navigation, alos when I clicked on LNAV button there was a message on the FMC saying something about intercepting I can't remember what it was.

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Hey Selbio,I suspect that the reason you can't engage VNAV is because you might have an altitude set in the MCP window that is either at or below your current altitude. The VNAV won't engage unless it has somewhere to go. :) Most people don't realize that the FMC-driven VNAV will not over-ride the altitude setting on the MCP, so if you have 10000 set in the altitude window, the MCP will switch from VNAV to HOLD when it reaches that altitude...either on the way up or down! (this is a good thing) I've been biten by that one more than a few times when I was first learning how to fly this beast! :)As for the LNAV, if you are getting the "Not on an intercept course" message on the FMC and LNAV won't engage, its because the current waypoint is behind you and your present course is taking you away from it.Just do a "Double tap" on the 1 LSK (or which ever waypoint you want to fly direct to) and press Exec and the course line will redraw and let you engage LNAV.And as Dan said, dig into those manuals! :)Regards,Steve Dra


Regards,

Steve Dra

Download my paints here at Avsim by clicking here

9Slp0L.jpg 

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Hehe, we posted at the same time!It looks like I guessed right about the "Intercept" message. :)Just set the altitude in the MCP window to your cruise altitude and you should be able to engage VNAV. Remember though, when its time to come down, you need to reset it (You'll get another message on the FMC to reset the MCP altitude when you near the T/D mark on the EHSI)Regards,Steve Dra


Regards,

Steve Dra

Download my paints here at Avsim by clicking here

9Slp0L.jpg 

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Sorry to ask too much but i just bought his product today and i'm not familiar with it at all, so what is the MCP and the 1LSK? One more question when do i use vnav and lnav?

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Hmmm,Ok, I will answer these questions, but this panel is as real as they get, and reading the manuals is absolutely mandatory to fly this plane...the answers to all your questions will be in there. :)The MCP is the "Mode Control Panel"...or the interface between you and the autopilot. Its the panel on the glaresheild that lets you control the aircraft via the autopilot.The "1LSK" refers to the top-left side push-button on the FMC, which when displaying the Legs page, denotes the current waypoint the FMC is programmed to fly to.By "Double Tapping" that key, you first put the waypoint on the "Scratchpad" at the bottom. Then pressing it again puts the waypoint "Back" into the plan and redraws the course line on the EHSI from your current position direct to that waypoint. If you try it and watch the course line on the EHSI, you'll see exacly what it does. :)As for when to use VNAV and LNAV, that is a matter of personal preference and/or Company(airline) policy. I can't tell you when you should engage them, you'll get the hang of when after you've flown the plane for a while.Even with hundreds of hours behind this panel, I still keep the manuals right by my side and use them continuously. I had to use a PLACE/DISTANCE/BEARING waypoint for the first time flying on VATSIM when I was re-routed and had to join another jet airway. Do you think I remembered how to do that? Hehe, nope, but I did remember that I read it in the manual once...and quickly found it. :) Regards,Steve Dra


Regards,

Steve Dra

Download my paints here at Avsim by clicking here

9Slp0L.jpg 

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