You have assumed... poorly.

 

As Matt stated also, pressing ALT INTV in that case will initiate an early descent (the equivalent of the DES NOW command on the FMC DES page), not a cruise descent to a new cruise altitude. That said, I've read around these parts that an early descent using ALT INTV will only be started when you're within 50 NM of your calculated top of descent, although I haven't tested that assertion myself. Yet.

Nuts.

 

When I was typing that I had this feeling that I bet this thing doesn't work the same way going down as it does going up.

 

So what do I do? Do I go and dig through the FCOM and make sure? Nah. I just post anyway and make a fool of myself.

 

Not the first time.

 

Otherwise, good to know I can use that from now on for DES NOW.

 

 

I guess I will also no longer be adjusting the pressurization controller after step climbs either.

 

So what do I do? Do I go and dig through the FCOM and make sure? Nah. I just post anyway and make a fool of myself.

Welcome to the club. :lol:

I've already tried re-entering the new (lower) cruise alt in the CRZ page. The FMC immediately switches over to the DES page and the CRZ page goes blank again. PROG page now only shows E/D, not T/D.

I've already tried re-entering the new (lower) cruise alt in the CRZ page. The FMC immediately switches over to the DES page and the CRZ page goes blank again. PROG page now only shows E/D, not T/D.

Were you in level flight or at least above the new cruise? Hmmm. Maybe try ALT HOLD and then re-cruise and then VNAV. . . just guessing now. I think RW it should work as previously described.

Were you in level flight or at least above the new cruise? Hmmm. Maybe try ALT HOLD and then re-cruise and then VNAV. . . just guessing now. I think RW it should work as previously described.

I'll try it again later. Maybe I did something out of order. If I remember correctly, I:

 

-Dialed the MCP from 36000 to 34000

-Selected V/S -500 for a smooth and gradual descend

-Got "OFF SCHEDULE DESCEND" light so I changed the Cruise Alt from 36000 to 34000 on the overhead, but that's irrelevant

-Passing 35000, VNAV goes into Descend mode (T/D deleted, vertical path indicator now shows on the Map display)

-Tried entering "340" in the now empty CRZ page. As soon as "340" is entered in, the page change from CRZ to DES.

 

Would you do anything differently?

 

I've already tried re-entering the new (lower) cruise alt in the CRZ page. The FMC immediately switches over to the DES page and the CRZ page goes blank again. PROG page now only shows E/D, not T/D.

The cruise page should become active again when you reach the new cruise altitude that you entered. The "TD" should remain on the ND the whole time. That's how I ensure we are going to get to the new cruise altitude before the new calculated TD in the real plane. In the NGX I always wait until TD to start my descent so I'm not sure how it behaves. I will play with the cruise descent when I get home to see if it matches the real plane.

I've compared what happens in the real plane and NGX and they both work the same.

Good to hear.