Hello, I would like to use the VNAV, but every time I activate it after take off, it takes me to FL10 where it holds the Altitude and then it engages automaticilly to the LVL CHG. When I reclick on the VNAV-Button happens nothing, there just appears a message on the FMC which says "check alt tgt" I hope you can help me. Regards

Altitude window on the MCP. What's it showing?

The VNAV will not fly to an altitude higher or lower than what you dial into the MCP(auto-pilot panel).LOL we have a Mexican stand-off version NGX

thanks I that was the problem, but I thought that the VNAV will climb/descend to each of the waypoints, why do I need this?

The window becomes a restrictor. Maybe your cruise is at FL300, but you're only cleared up to 10000ft after departure. With the altitude set on the altitude window on the MCP, you'll restrict the climb until further clearance.

Hm. I had the MCP now 30400, CRZ ALT FL250 at 26000 happened exactly the same :/, is this normal?

if you change the altitude to a higher one, you need to press on the top of it! It's not a scroll activation, it is a push activation which can be a bit hard to achieve, but if you push it at the top a bit off to the right, you should be ok... The VNAV is made this way for a reason! Even though you are programmed to fly at say 36 000FT the FMS cannot just climb regardless of ATC restrictions, so you dial in those restrictions as they are handed out by ATC: "Climb FL260" you dial in 26000 and the plane climbs to that cleared altitude. Then you have to receive a clearance in order to fly higher, and so the VNAV respects this. Hope this helps

Hmmmm.....I just had something like this happen :(  I am in VNAV mode, and the plane won't climb.  I have tried several things, but no luck.  My speed is severely resticted when I try to increase my altitude via the mcp.  Right now I am level at fl260, but wanted FL360.  When I try to increase the altitude on the mcp, the plane does not climb.

Never had this happen before?!  I have to disconnect my autothrottle and use my yoke to control the speed.  Otherwise with autothrottle engaged, the plane just keeps getting slower.  It almost seems like something is causing drag, but I have checked flaps, spoilers, gear.  I am at a loss :(

Seems like something got royally screwed up in the fmc.

The recall shows "FMC" in white letters, but not sure how that might apply :(

Sorry, this was meant for the 777ER.  Can this be moved to the 777 forum?!

Seems like something got royally screwed up in the fmc.

 

I don't mean to be offensive at all by this, but when it comes to automation not behaving "as expected," the one most prone to errors (the person) is usually the actual problem.  In the IT industry, we call this PEBKAC (problem exists between keyboard and chair).  In the aviation maintenance world, they sometimes say "problem exists at yoke-chair interface."  In other words, it's common to find the error in the human.

 

My bet is that you allowed the plane to kick out of VNAV, and into another mode with the SPD window opened to a very low speed.  That, or there was some odd entry in the LEGS page that needed to be passed or cleared that never passed or cleared.

 

 

 

The recall shows "FMC" in white letters, but not sure how that might apply

 

It's not related.  This is being discussed in the 777 forum, actually.  The *FMC message just shows to let you know that the FMC has pending data upload (wind, perf data, or altn list update).

Believe me, I wish I knew how I did it.  Don't think for a second, I was blaming the plane   But I am in flight now and am trying to fix the issue.  I think I tried to do a step climb by mistake.  But not sure how to cancel that action.

 

 

But not sure how to cancel that action.

 

Reset the cruise alt on the cruise page...

Hm. I had the MCP now 30400, CRZ ALT FL250 at 26000 happened exactly the same :/, is this normal?

 

If the airplane is between the FMC target altitude and the altitude selected on the MCP VNAV will not engage.  In your example if you wanted the airplane to descend to the FMC altitude of FL250 you would need to set the MCP altitude to FL250 or lower.

Yeah, I know all this guys, but for whatever reason I couldn't get it to work.  Anyways, it only did it once ever and all has been fine before and since.  I assume I did some sort of combo of things in the FMC and screwed it up somehow and got p'd off and couldn't think straight

Thanks for everyone's input though.  Always appreciated

 

 

Reset the cruise alt on the cruise page...

Yep...the quick fix (without the great explanations in this thread):

• head to your FMC (Shift-3)
• click the 'CRZ' button on the FMC
• reset the cruise altitude to something close to where you actually are.

 

This should then allow you to activate the VNAV button on the autopilot.

Hi,

 

Wow, you dug up a 2-year old topic! 

 

By the way, full names are requested on that forum.