The lateral control law used to capture a leg, when NAV is engaged, depends on the leg to be captured.
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For heading legs, the heading control law is used to capture the desired heading.
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For course legs (except CF leg), the track control law is used to capture the desired track.
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For a DF leg, the fixed path control law is used.
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For other legs, two cases occur. If the current track angle error is greater than 90., the leg is captured using the fixed path control law. Else, the crosstrack error is compared to the crosstrack limit. If crosstrack error is greater than crosstrack limit, then the heading control law is used to hold the current heading until the crosstrack error equals the crosstrack limit when the fixed path control law is used to capture the leg. Else the fixed path control law is immediately used to capture the leg. If the flight plan is changed while in a capture procedure, the capture rules are superseded by the control law that would normally apply for the new active leg.
PERFORMANCE/VERTICAL FUNCTIONS - DESCRIPTION AND OPERATION
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1. General
_______ The vertical functions and performance computations are available from a defined lateral and vertical flight plan. They enable: - optimization of the vertical profile inside all limitations (such as speed
envelope and constraints),
-estimation of fuel consumption and corresponding time,
-guidance according to the optimized vertical profile. Flight phases enable flight plan sharing in order to isolate different computations and guidance modes. They are given with appropriate switching logics. Then speed generation is described, with first speed envelope, reference and optimized speeds to be used in predictions and guidance in SPEED AUTO CONTROL mode. And then follows manual speed mechanization for MCDU preselection, FCU display and guidance in SPEED MANUAL CONTROL mode. The vertical flight plan management deals with computation of flight plan predictions and vertical guidance. A phase-by-phase description is followed by specific rules which apply in SPEED MANUAL CONTROL (FCU selected speed), VERTICAL MANUAL CONTROL (V/S, FPA, OPEN CLB, OPEN DES, EXP CLB or EXP DES modes) and LATERAL MANUAL CONTROL (HDG or TRK mode). Additional computations are also given, which are used by previous functions in normal cases (altitude, fuel, weight management) or in special cases (engine out, holding, alternates).
2. System Description
__________________
A. Flight Phases
(Ref. Fig. 001, 002)
(1) Introduction The flight plan is divided into several flight phases for which specific operations, predictions and guidance are defined. These flight phases are predicted to be for the active Primary F-Plan (flight phase logic is described in Para. 2.A.(2)):
Vertical F-PLN Definition
Figure 001
Flight Phase Display on PERF and PROG Pages
Figure 002
-PREFLIGHT : aircraft on ground, primary flight plan data are entered
-TAKEOFF : initial climb from the origin runway up to acceleration
altitude
-CLIMB : from acceleration altitude up to the top of climb at the
cruise flight level. It can include a climb speed limit,
and several altitude and speed constraints
-CRUISE : from the top of climb to the top of descent. It can include
a step climb or a step descent if a step flight level is
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