View Full Version : NGB737 VNAV (DESCEND NOW)

12th Jul 2001, 16:08
When one initiates a descent before the computed ToD using the DESCEND NOW LSK, and the aircraft starts the -1000fpm descent until it meets the computed descent path, what is the speed used for this initial portion of the descent?

Is it the CRUISE target speed, or the speed profile entered in the VNAV DES page?


12th Jul 2001, 16:35
A320 would use des speed if within 200 nm of dest otherwise cruise speed, don't know if 737 uses same philosophy..

12th Jul 2001, 17:42
I would say VNAV spd entered on the DESCEND page. Only during a VNAV CRZ descend ( new CRZ ALT selected ) it keeps CRZ spd as a target.

To be sure I'm gonna try tomorrow.

12th Jul 2001, 18:00

Thank you for your reply.

To be sure I'm gonna try tomorrow.

Waiting for the results :)


13th Jul 2001, 23:53
Track, quite correct. 1000fpm at the VNAV target speed.

Best rgds

14th Jul 2001, 00:12

I am still confused :confused:

You say it should use 1000fpm at the VNAV target speed, but whichTGT SPD are you referring to? The one entered in the VNAV CRZ page, or the one(s) entered in the VNAV DES page? This is what the initial question was about, which of the two TGT SPDs are used during the -1000 fpm descent portion.

Anyway, thanks for replying


14th Jul 2001, 00:50
Tried it today:

VNAV CRZ speed was ECON (.791) and I selected a VNAV DESCEND target speed of .760/280 in the DESCEND PAGE.

After executing DES NOW on the VNAV DESCEND page it decelerated to .76 in a VNAV PTH descend with 1000fpm.

After selecting the cleared level in the CRZ page it stayed in a VNAV PTH descend ( FMC showed CRZ DESCEND ) but started accelerating to ECON CRZ speed.

Not sure if this is the same for all updates (think we use 10.7).

Long story but it proves my earlier thought to be correct.

14th Jul 2001, 01:10
Thank you for remembering to verify this Track! I am obliged.