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MacAviator

LNAV and VNAV not disengaging

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Engaging LNAV and VNAV is no problem. Pressing the LNAV and VNAV buttons a second time or a hundred times does not disengage it. I have to change modes or disengage the autopilot altogether. Anyone having this problem?


Derek

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 Anyone having this problem?

No,

I have the same behiour as you, which is by design. Either engage another mode - e.g. another mode similar to Lnav would maybe go into hdg sel.

From vnav you'd go flch or v/s.

- or - most unlikely you'd do this, switch off the flight directors (any maybe a/p) but really, you'd want another mode.

Thanks


Carl Beeby

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Is it by design?

 

This is from the manual:

 

VNAV deactivated: • by selecting TO/GA, FLCH SPD, V/S, FPA, ALT or G/S pitch mode • if dual FMC failure

VNAV is disarmed by: • pushing the VNAV switch a second time, or • arming APP

 

LNAV deactivated: • by selecting heading hold (HDG HOLD) or track hold (TRK HOLD) • by selecting heading select (HDG SEL) or track select (TRK SEL) • when localizer captures • with dual FMC failure (LNAV may be re–activated if there is an active CDU ALTN NAV route available)

 

LNAV is disarmed by pushing the LNAV switch a second time, or by arming LOC or APP.

 

It says pushing it a second time should disarm it.


Derek

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On  the ground  to can turn them off and  on but  once in the  air   you have to select  another  mode


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Peter kelberg

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Macaviator,

 

Could you please tell me where to find that information about disarming LNAV and/or VNAV in flight, and in which manual? I have only just started learning to fly the 777 after many hours on the 737ngx.

 

Thanks

 

Dennis Hickman

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if dual FMC failure VNAV is disarmed by: • pushing the VNAV switch a second time,

 

The VNAV mode can be deactivated by pressing the VNAV button IF you have a dual FMC failure as you quoted in your post, not in normal situation.

 

 

 

Macaviator,

 

Could you please tell me where to find that information about disarming LNAV and/or VNAV in flight, and in which manual? I have only just started learning to fly the 777 after many hours on the 737ngx.

 

Thanks

 

Dennis Hickman

 

These modes are fully described in the FCOMv2 and the FCTM.


Romain Roux

204800.pngACH1179.jpg

 

Avec l'avion, nous avons inventé la ligne droite.

St Exupéry, Terre des hommes.

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Could you please tell me where to find that information about disarming LNAV and/or VNAV in flight, and in which manual? I have only just started learning to fly the 777 after many hours on the 737ngx.

 

The above information was misquoted, as Romain mentioned.

 

You can either select a different mode, or you can kill the F/Ds entirely to reset the system. Not sure why you'd want to specifically disarm either without selecting a different mode, however.


Kyle Rodgers

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Thanks Kyle for your quick response. The reason why I wanted to be able to cancel LNAV and/or LNAV was that there are occasions when I would like to take over flying the aircraft manually, typically on the approach if I want to deviate from the STAR (when not online). Maybe I have not really understood something fairly basic!

 

I have got so used to flying the 737NGX with over 500 hours logged, so I need to get more into the 777. I have on line access to all the PMDG documents for this aircraft, and have printed off copies of the Introduction and Tutorials 1 and 1.5.

 

As I see it I really need to do more study, as I am sure its all there in the manuals!.

 

Dennis Hickman

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If you want to fly the aircraft manually, then you just have to disconnect the A/P using the AP disconnect switch on the yoke, no need to deselect the modes.

 

However if you want guidance from the F/D while flying manually out of the route/STAR, just select the HDG SEL mode on the MCP and set whatever heading you like.

Or you can also turn both F/D off and fly raw data.


Romain Roux

204800.pngACH1179.jpg

 

Avec l'avion, nous avons inventé la ligne droite.

St Exupéry, Terre des hommes.

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