2 Thrust reduction altitude - Acceleration altitude
_ (Ref. Fig. 012)
-
The thrust reduction altitude is the altitude at which the pilot-selected takeoff thrust may be reduced to the climb thrust.
-
The acceleration altitude is the altitude at which the aircraft begins accelerating towards its initial climb speed.
-For the engine out case, only an acceleration altitude (EO ACCEL ALT) is defined.
-Reference altitude. It is undefined until it can be calculated as follows : For Takeoff: It is the origin waypoint elevation (if it exists). If not it is the aircraft altitude at transition to takeoff. For Go Around: It is the destination waypoint elevation (if defined).
-If the reference altitude is defined, the default values for Thrust Reduction and acceleration altitude are: Thrust reduction altitude = 1500 + reference altitude Acceleration altitude = 1500 + reference altitude.
3 Constraints
_ There are two types of constraints:
-altitude
-speed
-time
Constraint may be entered and modified through the F-PLN A
page or the Vertical Revision page.
(Ref. Fig. 013, 014)
Only one time constraint may exist in the same F-PLN (active or secondary).
Perf TAKEOFF Page
Figure 012
F-PLN A Page
Figure 013
Vertical Revision Page
Figure 014
On the F-PLN A page, the constraints (altitude, speed, time) are displayed with a star near the predicted value at the constrained point. If the constraint is predicted to be missed, the star is in amber color, else it is displayed in magenta color.
a Altitude constraint
_ It is an A/C altitude requirement to be met over a specified waypoint in the lateral flight plan. It can be an AT, AT or BELOW, AT or ABOVE or altitude window constraint. An altitude constraint may be defined in Altitude or in Flight level. It is defined in Altitude below the departure transition altitude (in climb) or the arrival transition altitude (in descent). Else, it is defined in Flight level. An altitude constraint is predicted missed if the aircraft cannot satisfy the constraint. In that case, the difference between the predicted altitude at the constrained waypoint and the altitude constraint value is displayed on the Vertical Revision page (if the difference is greater than 250 ft. or as long as it remains greater than 200 ft.). There are two types of constraint : climb and descent constraints defined as follows
-
When the aircraft is not in CRUISE yet, if a constraint is set at a waypoint: prior to T/C (if it exists) or belonging to SID or prior to a climb alt or speed constraint waypoint, the constraint is a climb constraint.
-
When the aircraft is not in CRUISE yet, if a constraint is set at a waypoint: beyond T/D (if it exists) or belonging to a START or beyond a descent alt or speed constraint waypoint, the constraint is a descent one.
-
When the aircraft is in CRZ, DES or APPR phase, if a constraint is set at any active primary waypoint, then it is a descent one.
-In other cases, the pilot has to choose the type upon entry of the constraint.
4
_
b Speed constraint
_ The speed constraint is an AT or BELOW constraint, defined at a specified waypoint.
-
If it is related to takeoff or climb (climb type
constraint), it applies from the origin up to the
waypoint where it is defined.
-
If it is related to missed approach, it applies from the destination up to the waypoint where it is defined.
-
If it is related to DES or APP (descent type constraint) it applies from the constraint waypoint down to the destination.
-
If it is related to manual holding pattern, it is used for the holding target speed computation.
-The speed constraint is predicted missed if the difference between predicted speed at constrained waypoint and speed constraint value is greater than 10 kts and as long as this difference remains greater than 5 kts.
c Time constraint (option)
_ It is a time requirement to be met at a specified waypoint in the lateral flight point plan. A time constraint can only be manually entered by a pilot. At most two time constraints may exist in the system (one in the active flight plan and one in the secondary flight plan). A time constraint is predicted missed if predicted time minus time constraint exceeds 2 minutes.
d Estimated take-off time
_ At origin airport, during preflight, the pilot may also enter an estimated takeoff time (ETT) defined as time initialization for predictions. If during preflight, no ETT has been entered and a time constraint is entered, the system computes an ETT which can be modified.
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