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Knoppie

LNAV and VNAV problem

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Hello everybody! I was wondering if someone could give me some pointers on things I'm possibly doing wrong. For all he flights I've made so far, including the tutorial flight twice, I've never managed to fly with the LNAV and VNAV path, it simply wont 'take over control'. Before I start my take-off roll I ensure that both Flight directors are set ON, Autothrottle is ON and VNAV and LNAV are both selected and green.Furthermore, the CDU has no discontinuinities, the route entered is a purple color, the CDU has calculated all the speeds and altitudes for the legs. Trim is set, flaps are set, all is well... When I start the take-off roll I apply about 40% thrust before engaging the TO/GA mode with CTRL-SHIFT-G, as stated in the tutorial. Then the throttles will go up normally, TO/GA mode is present on the MFD as well. But what happens is that both VNAV and LNAV are going off, the knobs are no longer lit and the MFD has no recollection of both ever present. Neiher of them can be engaged once airborne (knobs will lit up and LNAV and VNAV both appear on the MFD but no automatic action to follow the path is been taken) So: my question is: What the heck am I doing wrong??? Oh and by the way, PMDG did a great job with this 737NGX!! Regards, Maarten Knoppert


Maarten Knoppert

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Maarten, The lights going off the LNAV/VNAV buttons is perfectly normal. However, you should still see LNAV and VNAV in white on the FMA. Are you saying you don't see them on the FMA at all after you press TOGA? Any chance you can post some screen shots? One before you press TO/GA, one after you press TO/GA, and then one once you're above 400 feet would be helpful.

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The lights going off the LNAV/VNAV buttons is perfectly normal. However, you should still see LNAV and VNAV in white on the FMA.
Thank you Mike for giving me some help! Today I managed to make a normal flight. I think it was because either I tried to engage LNAV and VNAV again while I was taking off, or I was flying to far off the vertical beam, so too far off the VNAV path to be engaged propely with the CMD A button.

Maarten Knoppert

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