PPRuNe Forums - View Single Post - 757/767 VNAV descent path angle during deceleration

20th Jun 2020, 11:19

#7 (permalink)

firstmrj

Join Date: Jan 2015

Location: Far east

Posts: 10

Likes: 0

Received 0 Likes on 0 Posts

Quote:

Originally Posted by wondering

The same is true for the 787. It almost always ends up fast/high at lower altitudes when descending in VNAV. Could it be that using speedbrakes at lower altitudes is overall more efficient than descending earlier and not using speedbrakes at lower altitudes? That´s what one of my colleagues is suspecting.

I find it very interesting thought.
As far as I know Boeing/Honeywell doesn't disclose any models including coefficients variables.
I really want to ask about the calculation formula FMS is using to someone from Honeywell or Boeing.
Does someone in this community know anything about the logic VNAV is using?

Last edited by firstmrj; 20th Jun 2020 at 11:46.

Reply