re-engagement after the constraint is passed). Note that FCU selected altitude always has priority over the FM altitude target.
(2) Phase-by-Phase Presentation
(a) PREFLIGHT phase
1_ Predictions
Predictions for the active primary flight plan are computed
from origin to destination, provided that takeoff weight, CI,
and CRZ FL have been entered.
Before the engines are started, predictions are based on
entered ZFW and block; thereafter computed FOB is used.
2 Guidance
_ The following modes are armed automatically when at least one FD is engaged:
-ALT if FCU ALT less than or equal to ACCALT, CLB otherwise
-NAV if a Primary F-PLN exists and no HDG preset as been made
(b) TAKEOFF phase (Ref. Fig. 009, 010)
1 Takeoff parameters
_
a Takeoff speeds
_ Before pushing the throttle control levers forward, the pilot must enter the takoff speeds (V1, VR, V2) on the PERF TAKEOFF page. V1, V2, once defined, are displayed on the PFD speed scale. V2 is also used as target speed for guidance during takeoff (the SRS control law targets V2 + 10kts). The system also computes the flap retraction, slat retraction and final takeoff speeds versus takeoff gross weight. These speeds are displayed on the PERF TAKEOFF page (Ref. Para. 2.B).
b Takeoff thrust
_ During preflight, the pilot may enter a Flex Takeoff temperature on the PERF TAKEOFF page. If entered, the value is sent to the FADECs. During takeoff, if the throttle control levers are set on the Flex Takeoff position, the ECU uses the Flex Takeoff temperature to compute the Takeoff thrust.
Display of Takeoff Parameters
Figure 009
F-PLN Predictions
Figure 010
c_ Takeoff altitudes
Thrust reduction and acceleration altitudes are displayed
on the PERF TAKEOFF page. Their definition and revision
rules are given in 22-71-00.
d Flap/slat and THS position at takeoff
_ The pilot can enter the flap/slat and THS position for display only. All these parameters are frozen after transition to Takeoff phase.
2 Predictions
_ Takeoff predictions are based on the assumption that the aircraft will climb using takeoff thrust (either MAX TAKEOFF or FLEX TAKEOFF) maintaining a CAS of V2 plus 10 kts until reaching the thrust reduction altitude. At the thrust reduction altitude, the thrust is decreased to the MAX CLB value and V2 plus 10 kts is maintained until the aircraft reaches the ACCELERATION ALTITUDE which is the assumed end of the takeoff phase.
3 Guidance
_
-The only vertical guidance mode during TAKEOFF is SRS: if another mode is engaged, there is a flight phase transitions to CLIMB.
-
At thrust reduction altitude the CLB indication flashes on the PFD until the throttle control levers are set to CLB.
-
At acceleration altitude, there is a flight phase transition to CLIMB. If CLB mode is armed: CLB mode engages if NAV mode is engaged, if not, OPEN CLB mode engages. (Ref. Fig. 011)
(c) Climb
1 Predictions
_ Predictions are based on an optimum climb strategy taking all climb constraints into account. The optimum climb is performed by holding the Max climb thrust and ECON speed (i.e. optimum or time constraint speed limited by all applicable climb speed constraints and speed limit). But if this climb is above an AT or AT OR BELOW constraint, a level segment is inserted at the constraint altitude until the constraint point. No specific strategy applies to satisfy AT OR ABOVE constraints. In case of conflict between constraints, the first (laterally) encountered has priority. (Ref. Fig. 012)
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