Descent in VNAV stops

[Vargveum 53]

No, in the above example, the current constraint is the FL200 set in the MCP. Pressing ALT INT will only affect that.

 

However, lets's say you've done that and are on your way down to FL100 (for example) with 10000 in the MCP - and there is a waypoint alt constraint of FL150 over XYZZZ. Then, ALT INV will delete that constraint in the FMC.

[MED1473 18]

Ok, perfect!

Thank you guys!

[Spin737 102]

Matt- brilliant! I defer to your ascerbic and thoughtful insight into this issue. Perhaps you are correct, I am not on the same page? Do enlighten us with your thoughts, however, I am acutely interested. I wait in hopeful anticipation.....

 

Matteo- I would advise you to disregard my response, apparently it is inaccurate. Do however check back, Matt is on the case.....

 

Clearly you misunderstood the OP and I politely pointed that out. No flames, just facts.

[MED1473 18]

Ok guys no reason to start bickering about nothing, my qestion has been answered, greatly I say and in depth. I've understood everything I needed and this post has reached its purpose!

I am just a bit puzzled Mat on how has Carl misunderstood my first post? I think everyone here has got what I meant and it seems it is you that perhaps think differently. I was talking precisely about flying away from MCP alt once reached it! On top of that Carl and the others took the time and effort to write an exhaustive, in depth answer that cleared my doubts. That couldn't really have happened if they ALL misunderstood my OP unless I've misunderstood my own post too... a distubing thought...

No offense.

Cheers, Matteo

[Spin737 102]

I think the question you asked was really about VNAV ALT. That's why I asked about the FMA. Most pilots and instructors will ask, "Well, what did the FMA say?" when trying to answer questions about auto-flight.

 

Carl and many of the other posters gave you good advice - reset the MCP and hit ALT INT.

 

Here's the sections you need:

 

• VNAV ALT – when a conflict occurs between the VNAV profile and

the MCP altitude, the airplane levels at the MCP altitude and the pitch

flight mode annunciation becomes VNAV ALT. VNAV ALT

maintains altitude.

 

During descent, VNAV ALT engages if the airplane levels at an MCP altitude not

in the FMC.

 

Altitude Intervention (ALT INTV) Switch

Allows manual deletion of next FMC altitude constraint via altitude SEL and ALT

INTV switch.

Push – (during VNAV climb)

• lowest FMC altitude constraint below selected MCP altitude is deleted

• if airplane is currently at an FMC altitude constraint, deletion allows

airplane to resume climb. MCP altitude must be set above current altitude

• for each press of switch, one deletion occurs

• if MCP altitude is set above current FMC altitude, FMC cruise altitude

resets to MCP altitude. FMC cruise altitude cannot be decreased using

ALT INTV switch.

Push – (during VNAV cruise)

• if MCP altitude is set above current FMC cruise altitude, FMC resets

cruise altitude to MCP altitude and initiates a cruise climb

• if MCP altitude is set below current FMC cruise altitude, an early descent

is initiated. Lower FMC cruise altitude cannot be entered using ALT

INTV switch.

Push – (during VNAV descent)

• the highest FMC altitude constraint above MCP altitude is deleted

• if airplane is currently at an FMC altitude constraint, deletion allows

airplane to continue descent. MCP altitude must be set below current

altitude

• if all FMC altitude constraints are deleted during VNAV path descent, an

automatic transition to a VNAV speed descent is made.

 

I hope that info adds to the discussion.