NGB737 VNAV (DESCEND NOW)

[Stamatis]

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?

Stamatis

[OLBA18]

A320 would use des speed if within 200 nm of dest otherwise cruise speed, don't know if 737 uses same philosophy..

[Track]

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.

[Stamatis]

Track,

Thank you for your reply.

To be sure I'm gonna try tomorrow.

Waiting for the results

Stamatis

[Slick]

Track, quite correct. 1000fpm at the VNAV target speed.

Best rgds

[Stamatis]

Slick,

I am still 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

Stamatis

[Track]

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.
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Track

[Stamatis]

Thank you for remembering to verify this Track! I am obliged.

Stamatis