Ever since I've gotten the NGX, I always prearm VNAV (and LNAV if necessary) on the ground before takeoff. Compared to my previous experience with the NG in FSX, most notably the iFLY, this sure makes my workload so much easier, so much so that I feel like I'm cheating. But this has gotten me thinking, which real world carriers prearm? I also read that there is a glitch in the software, and Boeing had issued a directive instructing users to enable VNAV only after flaps are retracted on climbout.

 

I mainly fly Southwest routes, or Delta and American. Does anyone know if those carriers manually enable VNAV in the air vs. on the ground?

Hi! I can't speak for those carriers sops, but normally I arm them when in the air, only once during a late night dep, I have armed the LNAV. :-) But its up to you as a commander of the a/c what you do, it's your responsibility to communicate it out to the f/o what you intend to do, if you are the PF. ;-)

 

Jakob

I usually select VNAV and LNAV when I am around 1500 feet , follow the flight director for a while and the turn on Autopilot after a bit of manual flying.

I heard that VNAV is not allowed to be armed while on the ground, only LNAV is.

 

VNAV can be activated or armed from 800ft AGL.

I have seen pilots only having LNAV armed. And once they are in the air, they press the N1 button at 1500 feet, and after the altitude restriction (if there is one), they use VNAV.

With the current software revision of the FMC which is present in the NGX, Boeing standard procedure is to arm VNAV prior to departure. Of course, that's not a strict requirement and you as the captain can do whatever you want, but Boeing says to arm VNAV prior to departure. LNAV can be used however you want. Personally, if I'm flying a complex RNAV departure, I arm both VNAV and LNAV. If it's a simple vectors to first fix/assigned route, I skip LNAV but still arm VNAV.

 

I don't know what the real world operators do, but I surmise they would follow the Boeing SOP.

I arm both on the ground. I do note however that after pressing TO/GA, the VNAV and LNAV lights go out and don't come back until I'm airborn. I can't remember when exaclty they come back. So my guess is that the system prevents you from actually using VNAV and LNAV when your too low. Once you have the altitude, it comes alive and then you can activate autopilot. Just my observation.

I've flown at two airlines that have the NG. At one, we had FMC U10.8a and would arm VNAV on the ground. At the other we have U10.7 and that version does not allow VNAV on the ground.

 

With the NGX, if you are doing NADP-1 (3,000AGL accel ht), there's no reason to not use VNAV. It's easy and it works very well. If you are doing NADP-2 (1,000AGL accel ht), there are a few different ways of flying it, but it can be done in VNAV or TOGA->LVL CHG.

 

Separate any questions of LNAV and VNAV. They are completely separate other than the last three letters of the name. You can arm one, or the other, or both as needed. You might as well be asking, "Can I have a landing light on and use LNAV?" Of course, they are totally separate.

I usually select VNAV and LNAV when I am around 1500 feet , follow the flight director for a while and the turn on Autopilot after a bit of manual flying.

 

Ahh yes the manual flying, flying it to FL100. :-)

I use Collins MCP. Both VNAV and LNAV are pre-armable on the ground and I do so. I just like to have some guidance. Although LNAV kicks in only after 400 feet (I think).

Usually, I prearm LNAV when doing before take off checklist. Then I line up, advance to 40% N1, stabilize, up to take off thrust, press TO/GA, rotate at Vr, fly manually (following FD) until at least 1000ft AGL, engage CMD A (which automatically engages N1 and LVL CHG), at thrust red. (3000ft), I select flaps up speed and only after flaps are up, I select VNAV.

 

I believe this is standard OPS with TRA in the Netherlands (except they don't arm LNAV on the ground), correct me if I am wrong???

 

Daniel W.

This is up to the individual airline and can depend on the FMC revision they're using (obviously no airline using a version prior to 10.8A is doing it) - there is no prohibition against doing it - it's a feature Boeing added for a reason and arming it is in their normal procedures. All the Big Boeings do it this way too.

 

Less things for the crew to juggle during a critical flight phase is always a good thing and this helps with that.

747 many pilots arm both before t/o

I'm pretty sure (don't quote me on this) at Southwest, that you only arm VNAV on the ground if you are flying an RNAV departure (e.g., BOACH2 out of LAS). Other than that, VNAV shouldn't be engaged until the flaps are completely retracted, which occurs above 1000ft AFE.

I arm both on the ground. I do note however that after pressing TO/GA, the VNAV and LNAV lights go out and don't come back until I'm airborn. I can't remember when exaclty they come back. So my guess is that the system prevents you from actually using VNAV and LNAV when your too low. Once you have the altitude, it comes alive and then you can activate autopilot. Just my observation.

 

I do the same, and the lights come back at 400 ft. AGL and then you can enable CMD A or B.

 

One of the nice things with Fs2Crew is that you F/O tells you when the VNAV and LNAV lights come back.