Just setting a few things straight here.

What's your departure like? If there's more than a 5 deg turn at departure then it won't arm on the ground (iirc!!)

That's correct, but doesn't affect VNAV. First leg after departure need be in a ±5° corridor for LNAV, not VNAV.

You don't engage vnav on the ground because toga commans heading select to keep the wings level.If you engage a pitch mode then you will exit takeoff mode !!

Yes you do arm VNAV on ground (should you opt to). This is new to U10.8. Of course it can't engage on ground. It will however automatically engage at 400R, just as LNAV would at 50R.

VNAV doesn't decend on its own for me, it only follows the altitude bug...

That's a bit of a weird way to say it. So you're actually not denying that VNAV descends. But of course it will only descend as far as your MCP altitude will allow. It will never ever go beyond that, neither climb nor descent (except for some special cases maybe, like flying a NPA with LNAV/VNAV and resetting altitude to MAP altitude with VNAV still remaining in final descent, but in that case you're "tricking" VNAV a bit and it's an entirely different topic anyways).As long as your MCP altitude is set to something lower than your cruise altitude before reaching T/D, VNAV in fact WILL automatically commence descent.

VNAV seems to work for me on the ground only when i enter 30c or somthing like that for a temp. on the FMC takeoff page. -Travis

I thought it was fairly normal to have it not come on , when on the groundin *some* cases. I usually can turn both on when on the ground. But I'vehad a few cases where they would not. I don't think it's a glitch.. I think thereal world version will do that too in some cases.. Or I think anyway.. :/In all the cases where it would not light on the ground, I had no problemsenabling them once airborne.Most of the time, both arm on the ground.. But if it doesn't, I don'tworry about it. It will later. Or has in all my cases.Maybe one of the RW pilots will chime in..

Just setting a few things straight here. That's correct, but doesn't affect VNAV. First leg after departure need be in a ±5° corridor for LNAV, not VNAV. Yes you do arm VNAV on ground (should you opt to). This is new to U10.8. Of course it can't engage on ground. It will however automatically engage at 400R, just as LNAV would at 50R. That's a bit of a weird way to say it. So you're actually not denying that VNAV descends. But of course it will only descend as far as your MCP altitude will allow. It will never ever go beyond that, neither climb nor descent (except for some special cases maybe, like flying a NPA with LNAV/VNAV and resetting altitude to MAP altitude with VNAV still remaining in final descent, but in that case you're "tricking" VNAV a bit and it's an entirely different topic anyways).As long as your MCP altitude is set to something lower than your cruise altitude before reaching T/D, VNAV in fact WILL automatically commence descent.

But if I'm at cruising altitude and move the bug, say halfway through teh cruise, is begins to descend when VNAV should calculate the path. This never happens in the 747.

But if I'm at cruising altitude and move the bug, say halfway through teh cruise, is begins to descend when VNAV should calculate the path. This never happens in the 747.

Strange, doesn't do that for me. I can change the altitude in the MCP window, but VNAV will not begin descending until I manually command it to descend or it reaches the calculated TOD point according to he flight plan.

Should not descend in VNAV until T/D. Only if you reset the MCP ALT andthen the ALT INTV button would it start a descent before reaching T/D.If you do lower the MCP ALT, and then ALT INTV before T/D, it will usuallystart a descent of around 1000 fpm. If it intercepts the VNAV path, it willstart to follow the VNAV path at that point if VNAV is selected.Forgot to say.. You may be accidentally clicking the ALT INTV buttonwhen resetting the MCP ALT. That would start the descent.

I'm not! I get to T/D and it doesn't descend! Unless of course i set the altitude bug to the desired altitude at the next watpoint. You guys are acting like I have to be making mistakes, I'm not!

I'm not! I get to T/D and it doesn't descend! Unless of course i set the altitude bug to the desired altitude at the next watpoint. You guys are acting like I have to be making mistakes, I'm not!

I think you just answered your own question there lol. To make vnav descend on the calculated vertical path you need to have a lower altitude set in the MCP altitude window.

But the whole point of VNAV, Vertical Navigation, is that it should calculate when the aircraft climbs and decends, how fast it does this, and it shoudl do this regardless of what altitude the MCP is in. In the legs section, it shows the altitudes that the aircraft should be at while pasing through every waypoint. If VNAV requires the changing of the MCP input, it is no different than flight level change. VNAV is supposed to work somewhat liek an ILS system, where it descends on a pre-determined path, not by manual input. Because if I want to be at say 8,500' for the FAITH intersection for an ILS into SFO's Rwy 28L, it should bring me to that altitude on time, rather than require me put in 8,500' then put in 7,000' feet for DIVEC when I start the ILS.

That's a safety function built into the fmc. It won't descend unless you give it permission (or run out of fuel). That's how the real thing works & how the ngx works.How anyone thinks it SHOULD work is irrelevant. They modeled how it DOES work.

So PMDG didn't do the 747-400 correctly? The way it works here makes it no different than the flight level change....

So PMDG didn't do the 747-400 correctly? The way it works here makes it no different than the flight level change....

I dont know what you're talking about. I always had to change the mcp alt before t/d in the 744.

Because the 747 and MD-11 work the way I describe

See previous post...

Well then there's some issues...