Lnav and Vnav enabled before takeoff?

[G7USL 117]

I use both PFPX and Top Cat for flight planning in order to get my flights correct but I am never able to enable Lnav and Vnav on the ground before takeoff?

 

Conversely, If I do the same for the 777 I have no problems.

 

Does anyone have a solution please?

 

 

Please don't just say "Oh your doing something wrong" as that is of no help at all.  Constructive comments though, are most welcomed and appreciated too.

 

Thanking you all in anticipation.

[Driver170 42]

First of all well done in using PFPX and TOPCAT

 

LNAV and VNAV to have these armed on the ground you need to have the FMC correctly setup for your route? Have you tried the tutorials and read the FCOM about these lateral and vertical modes its all explained.

 

Have you got both FDs on ?

[pcubine 143]

 

 

Please don't just say "Oh your doing something wrong" as that is of no help at all.

We don't know what you are doing so how could we say your doing something wrong. As Vernon Howells mentioned in post #2, the FMC needs to be setup correctly and the FDs need to be turned on. You will probably find your operator error in Tutorial 1 pretty early on. Try it and see if that solves your problem.

[thepilot 562]

It definitely is possible on the NGX to arm both LNAV and VNAV on the ground.

 

In reality, I have rarely seen it done, though. Norwegian Air Shuttle are actually the only ones I know of. Some carriers don't even activate LNAV until reaching 400 feet, generally.   

[Driver170 42]

Arm LNAV and VNAV and it pretty much takes care of everything

[codechris 9]

I could be wrong, but I think the Boeing FCOM recommends arming VNAV on the ground, but I never do. I have armed L nav on the ground but I'm not sure if it's made any difference. But yeah, don't bother arming them unless you have a reason in which to do it

[scandinavian13 5,192]

 

 

Does anyone have a solution please?

 

LNAV arming criteria on the ground:

•origin runway in flight plan

•active route entered in FMC

•track of first leg within 5 degrees of runway heading (this one is usually what trips people up)

•LNAV selected prior to TO/GA

•LNAV guidance becomes active at 50 feet AGL

•bank angle is limited to 8 degrees below 200 feet and 30 degrees above 200 feet AGL

 

If any of these conditions are not met, it will not be able to arm.

[G7USL 117]

You was right Kyle and others. I didn't have the FO's flight director on because everytime I look, he/she is missing. lol

[Driver170 42]

Easy mistake done now enjoy

[Andrea1 6]

Hi,

I usually arm LNAV on ground (if the criteria that Kyle has outlined are meet) but not VNAV (also if it's possible with NGX and Boeing FCTM reccomends it) : the (real) Airline SOPs I'm applying don't allow it..I think maybe for having procedures "commonality" with their complete fleet (you could have airplanes with software upgraded to last version and others with old software version not allowing that feature)

 

I use FL CHG till flaps rectraction (usually NADP1 3000 ft AGL)

 

Ciao

 

Andrea

[JoeDiamond 67]

We used to arm VNAV on the ground but our current procedure is to select VNAV at 1000' AGL.  Under certain circumstances having VNAV armed can cause a conflict with the predictive windshear alerting which is why we no longer arm it prior to takeoff.

[Copper. 78]

That bulletin was released some time ago. a little late to change your flying practices, I would've thought...

[JoeDiamond 67]

That bulletin was released some time ago. a little late to change your flying practices, I would've thought...

 

We changed it some time ago.  I don't recall saying it was a recent change for us.

[Copper. 78]

We changed it some time ago. I don't recall saying it was a recent change for us.

you're right. My apologies.

 

I haven't read that bulletin in a while, but if memory serves, you can arm vnav, but you've just got to press (click) toga a SECOND time to get max N1 if necessary for windshear escape... Is that right?

[JoeDiamond 67]

you're right. My apologies.

 

I haven't read that bulletin in a while, but if memory serves, you can arm vnav, but you've just got to press (click) toga a SECOND time to get max N1 if necessary for windshear escape... Is that right?

 

I'm not sure.  The procedure was changed before I was on the airplane so I have never done it the other way.  Would the FD still provide escape guidance in that scenario?  I'm heading down for recurrent training tomorrow.  I'll ask one of the schoolhouse guys about it.