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Guest Foizman

744: from HDG HOLD & ALT to VNAV/LNAV

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Guest Foizman

Hi Captains,can anybody help me? E.g. when ATC tells one to "Fly Runway Heading until 2500 then turn 30 degrees away from Center of Airport..." at this point the FMC should be allready programmed, so I don't wonna change the data anymore.So when I takeoff I use the Heading Hold Button and e.g. set 5000ft on the MCP. Autopilot active within seconds.Minutes later, I want to get back to the programmed profile of the FMC. How can I switch to VNAV/LNAV? Sometimes these buttons do not activate the desired modes, the PFD continues to show ALT and HDG HOLD. The 744 doesn't follow the programmed FMC-path, either.How can I reactivate the FMC-data or make the VNAV/LNAV-buttons work like expected, after I've used HOLD?greets,Foizman

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Guest Daniel Slade

Foizman,You need to be on a heading that will intercept with the planned route. E.g you are flying 000deg and your route is 180deg then you are going the wrong way and need to turn towards your route. Once the aircraft is facing the right way Lnav will engage.Lnav is for direction.Vnav is for height.Hope this helpsDaniel

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Guest dt1951

I don't remember hearing an ATC direction to fly 30 degrees from center of airport. But here goes. Don't have the LNAV button engaged when you takeoff. Sounds like you already have your altitude in the MCP so that should be fine. When you engage the autopilot it will hold your current heading (runway heading) until you select another lateral mode (heading or LNAV). You can have the new course already entered in your MCP. When you reach 2500', then press the center of the heading selector button to steer to the new heading. ATC should give you vectors to your first waypoint on your departure. If you don't have ATC by this time (which should be departure or arrival), then use the heading selector to steer toward your first waypoint. If you have been in the air for more than a few minutes then the odds are the intercept course to your waypoint will not be the same course as depicted on your HSD. In that case, before selecting LNAV you will want to do a "direct to" action in you FMC (do this on your legs page). This also applies if ATC gives you direction to fly direct to your waypoint. By just selecting LNAV the aircraft will steer to intercept the course from your previous waypoint (in this case the departure airport) to your next waypoint, and not a direct heading to your next waypoint.Hope this helps...

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Guest Foizman

ok thanks a lot, will try this tonightgreets,Foizman

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