Hi Guys: I still have a problem with the ngx following the designated spd/alt in the fmc legs pages are these only reference or is there a setting in the fmc I should be activating ? also can they be changed at will during the flight ? thank you.

Anyone ? thank you

Hi, Are you only talking about climbs or descents or both? It's unusual to have a VNAV specific issue like the one you're describing. You can also freely change speed and altitude on the legs page. You must however activate and execute your changes.

descents Erik, I have executed but it does not decsend to the next altitude, just stays at the original altitude of 5,000 all the way, it is a short flight from kbos to kpvd, thanks.

descents Erik, I have executed but it does not decsend to the next altitude, just stays at the original altitude of 5,000 all the way, it is a short flight from kbos to kpvd, thanks.

Have you set a lower altitude in the MCP ? If not the plane will obey the MCP ! Fred.

Fred left altitude in mcp at 5,000 thought fmc would override mcp while in vnav - lnav ?

Rich, the autopilot will not descend nor climb beyond what is set in the MCP altitude window. Before your Top of Descent, select a lower altitude on the MCP and let the autopilot descend on the VNAV path.

Fred left altitude in mcp at 5,000 thought fmc would override mcp while in vnav - lnav ?

No !!That's the problem a lot of people make. The MCP overides VNAV !! eg, Vnav is set to climb to 10,000 ft.If the MCP altitude is only 7000 ft the plane will level off at 7,000 ft. It is the same for decents. Fred.

Erik so would 2000 be a good alt before turn on final, its not a straight shot in my flight plan ? thanks pal. Actually is there an alt where the fmc will take over on the lower altitudes automaticlly ?Why is there spd/alt designations next to legs if mcp does all the work are they just reference

Erik so would 2000 be a good alt before turn on final, its not a straight shot in my flight plan ? thanks pal. Actually is there an alt where the fmc will take over on the lower altitudes automaticlly ?

If you capture the localizer then VOR/LOC will look after your roll mode.If you then capture the Glideslope, APP mode willl look after your Pitch and disengage VNAV automatically. You could also try an autoland with both autopilots engaged. Fred.

Tried vor/loc and app mode but the plane ends up on target but in the middle of the runway to high for landing oops, autoland with both autopilots engaged app mode turned on before the cmd "b" is engaged right? appreciate your help guys

Rich, 2000 to 3000 feet would be a good altitude to intercept a final approach course or an ILS to a runway. To answer your other questions: The FMC will never go beyond what you have set in the MCP altitude window. The speed/altitude designations next to the legs are simply there to update your VNAV path and force the airplane to cross those points at the preset restrictions. For example... If you're cruising at FL250 and have 3 waypoints along your STAR which have speed and/or altitude restrictions, the easiest thing to do is to lower your MCP altitude to the lowest altitude before you intercept the glide slope on an ILS approach. With VNAV engaged, the autopilot is working with the FMC and will know to abide by the restrictions you set for each leg. This is why you have a Top of Descent point determined somewhere along your route as the FMC takes into consideration the speed at which the descent should be conducted and what speed/altitude restrictions are set for each waypoint. You may have seen restrictions like 250/13000A or 250/13000B or 250/13000 next to waypoints in the legs page. Each of these means the autopilot will cross those points ABOVE, BELOW and AT 13000', flying at 250 knots, respectively. If the FMC determines you it cannot cross a waypoint by a certain altitude, you may get a DRAG REQUIRED message on the CDU prompting you to aid the autopilot in the descent. All while you're descending, the autopilot hasn't forgotten about the MCP altitude you've selected. Once you reach that altitude, the aircraft will level off in ALT HOLD. I hope this wasn't too confusing!

Great explanation so the spd/alt is a restriction to complete a good flight you have to use mcp to bring her down, if the mcp was at 2000 lets say half way to destination it would descend to the 2000 the fmc would have no control over it. great help guys. So in short I would have to use mcp to get to the correct altitudes through entire flight except autoland process.

Great explanation so the spd/alt is a restriction to complete a good flight you have to use mcp to bring her down, if the mcp was at 2000 lets say half way to destination it would descend to the 2000 the fmc would have no control over it. great help guys. So in short I would have to use mcp to get to the correct altitudes through entire flight except autoland process.

Hi Richard ! I think you are still a little confused about this. VNAV can fly your whole flight for you but if the MCP altitude conflicts with it you have a problem. The tutorial flight is a very good example of this. In other words the MCP will stop you climbing or decending in VNAV if the MCP altitude is not changed. A very simple example would be to have a cruise altitude of let's say 8,000 ft.Set the MCP to 8,000 so it does not stop VNAV from climbing.In your descent maybe set 3,000 so it can start to decend etc.............. Fred.

Got it Fred a perfect landing, vor/loc and then app right down the middle you have been a great help, thanks so much wow very exciting in this bird amazing aircraft, sounds are incredible, take care my friend.