777 VNAV and Altitude Constraints
Hi,
I have a question regarding the calculation of VNAV profiles and altitude constraints on the 777. In calculating the climb profile, altitude constraints along the route will be observed by the calculated VNAV profile. However, at some point, an altitude constraint on the route will become a constraint relating to the descent path, rather than the climb path.
In calculating the climb path, is there a specific rule which determines whether an altitude constraint in the route is treated as a constraint during the climb phase?
To illustrate by means of a simple example, suppose a route was entered from EGLL to KJFK consisting of great circle waypoints every 20nm. If an altitude constraint of 6000ft was entered on the first waypoint (eg 20nm out of EGLL) this would be treated as a climb constraint. Similarly a constraint at the 40nm point. How far out along the route would an altitude constraint stop being considered in the calculation of the climb profile? Is it related to the distance from origin, distance from destination or some function of the trip length.
Thanks in advance for any info.