More testing this morning. Think I have found a problem:

 

I've set up 2 almost identical flights. Both are RTO on runway 32 at EGNM. One's a 700, one an 800, so I can load them alernately for testing.

 

I've been through the FS2C flows to the Take Off item, identically in both cases.

 

VNAV and LNAV are NOT armed.

 

NADP = 1.

 

The difference in FMC programming is this: the 700 has an immediate turn to the right i.e. the first WPT is more than 5deg off runway heading. The 800 has a WPT 8m dead ahead.

 

Repeatably, this is what happens:

 

700 - using Heading Select, and VNAV after 3000 - all works as expected

 

BUT using LNAV at the roll mode select point LNAV does NOT activate. The button is off, and the PFD doesn't show LNAV as armed.

 

LNAV should, according to the FCOM, trigger in flight even if the first waypoint is more than 5deg off.

 

However, If I then manually fly the turn to the right, and at 3000' select VNAV and CMD A, then LNAV seems to remember it was selected, and BOTH now activate.

 

800 - the same, but of course there's no turn to fly, so LNAV never comes on.

 

I am 99% sure that all works as it should when you arm LNAV & VNAV on the ground, but of course you can't do that unless your first WPT is pretty much ahead - rarely the case in the plans I fly.

 

Any thoughts?

 

Paul Scholey

Hi Paul,

 

You might want to check with PMDG.

 

If LNAV is not coming on, it means the conditions have not been met for LNAV to activate.

 

Cheers,

Thanks Bryan - but LNAV works fine if I activate it in the air by clicking the MCP button with my mouse. It doesn't work if I use the FS2crew button to set it when I'm presented with roll modes. I can see the button is being depressed but it doesn't light up and LNAV doesn't illuminate.

 

Sorry if that wasn't clear from my post - hopefully it is now.

 

Paul Scholey

Hi Paul,

 

All FS2Crew does is "press" the same LNAV button via the SDK.

 

It's very simple.

 

So if LNAV didn't engage, something else was going on.

 

Cheers,

Bryan,

 

My apologies, you are right (of course!) - seems to be an altitude thing; haven't quite worked out the cutoff yet, but certainly if I wait till I'm 1000' AGL LNAV connects when I choose the roll mode. If I find the exact condition, I'll post if for others' reference. FCOM 2 reckons 50' but I'm pretty sure that's not happening - but it's nothing to do with FS2crew, whatever :)

 

Paul

Here is the definitive answer:

 

http://forum.avsim.net/topic/376993-lnav-from-50/

 

400' - then LNAV will engage.