AP/FD ENGAGEMENT - DESCRIPTION AND OPERATION

** ON A/C NOT FOR ALL

1. General
The engagement of the Flight Director (FD) and the Autopilot (AP) for flight guidance are described in this section.

** ON A/C NOT FOR ALL

2. System Description

A. FD Engagement

(1) General

FD Engagement

The FDs are engaged automatically upon energization of the computers in flight or on the ground.

(a) Energization on ground
After the safety tests, at power rise:

The two FDs engage if no failure is detected by internal monitoring.
The FMA indications appear on the PFDs but the FD bars are removed.
The FD orders will be displayed on the PFD for a given axis when a mode is active on this axis.
If an FD does not engage (FMGC failure detected by internal monitoring), the two PFDs are switched to the valid FD (same FD indication on both PFDs).

(b) Energization in flight
The safety test at power rise is not performed.
The two FDs engage in V/S and HDG modes.

(2) FD - Engage Hardware Logic

FD - Engage Hardware Logic

A part of the FD engage logic is accomplished through the hardware.
This logic takes into account the FD ENGD signals (generated in the software) and the FG HLTY signals from the command and monitoring channels:
Loss of the FD ENGD signal is spread over a period of 200 ms.
The safeguard of the engage signals is ensured by back-up current Vs over a brief period.
The CMD and MON FD ENGD wired signals which are obtained are used by:

The DMCs (FMGC bus selection logic).
The FCU (FMGC bus selection logic).
The opposite FMGC (FD COND logic).

(a) FLIGHT GUIDANCE HEALTHY logic (FG HLTY)

FG HLTY Logic

1 FG HLTY logic on command side
This signal which is consolidated by an FG HLTY signal from the monitoring channel is generated by the following monitoring functions:

a Internal monitoring of the guidance
This monitoring function comprises the result of the safety tests.
These tests are initiated on the ground at power rise (long cutoff) The devices to be tested are : the memories, the watchdog, the power supply monitoring circuit, etc.

Monitoring of the +5V, +15V and -15V powers (supplied from the aircraft 28 VDC)
This is a cross - monitoring between CMD and MON channels (the CMD side monitors the MON powers and vice versa)
Monitoring of the access to the INNER/GUIDANCE common memory
Monitoring of the ARINC input and output sequencers
Monitoring of the monitor ARINC transmissions
Monitoring of the real-time monitor of the inner loop processor
Monitoring of the alpha-floor logic.

b Internal monitoring of the inner loop CPU
This monitoring function comprises:

Monitoring of the ARINC input and output sequencers
Monitoring of the AP output orders
Monitoring of the INNER/GUIDANCE common memory
monitoring of monitor ARINC transmissions.

c Monitoring of the exceptions of the guidance CPU
An exception results from an instruction which cannot be performed normally for these reasons:

Either it does not follow the rules of the memory protection
Or it leads to an erratic result
Or the instruction itself is garbled.

d Monitoring of the exceptions of the inner loop CPU

e Guidance processor watchdog output

2 FG HLTY logic on monitoring side
This signal which is also consolidated by the FG HLTY signal from the command channel is generated by the following monitoring functions:

a Software monitoring of the monitor CPU
This monitoring function comprises:

Result of the safety tests
Monitoring of the +5V, +15V and -15V powers of the command channel
Monitoring of the ARINC input and output sequencers
Monitoring of the command ARINC transmissions
Monitoring of the AP orders
Monitoring of the FD orders
Monitoring of the alpha-floor logic.

b Monitoring of the exceptions of the monitor CPU

c Watchdog activation

(b) FD ENGAGED logic (FD ENGD)
Three conditions are required to obtain FD ENGD

1 FD specific conditions (FD COND)

FD Disengagement

This logic takes into account the actions on the FD pushbutton switches on the FCU

FG HLTY Logic

NOTE: The FD can be disengaged by means of the FD bars clearing pushbutton switches.

Two cases may arise:

a Both FMGCs valid
(FD1 on Capt PFD and FD2 on F/O PFD)
Action on one pushbutton switch results in:

Removal of the bars on the associated PFD
Disengagement of the corresponding FD.

b One FMGC not valid (the opposite FD is presented on Capt and F/O PFDs)
Action on one pushbutton switch results in:

Removal of the bars on the PFD associated with the pushbutton switch.

Action on the second pushbutton switch results in:

Removal of the bars on the associated PFD
Disengagement of the FD.

2 AP/FD common conditions (Ref. para. 2. A. (3).

3 AP/FD/A THR common conditions (Ref. para. 2. A. (4).

(3) AP/FD Common Conditions : AP/FD COND

AP/FD COND Logic

(a) FAC parameters monitoring
This monitoring takes into account the validity (refresh and status matrix) of the data on the bus selected by the FMGC.
Selection of the FAC bus is in function of the FAC HEALTHY wired discretes (two CMD and MON discretes per FAC).

The monitoring of the parameters linked to the flight envelope is not taken into account in LAND TRACK phase.
Parameters such as; weight, center of gravity, maneuvering speed in clean configuration, are not monitored in LAND TRACK or GO AROUND modes.

(b) Radio altimeter monitoring
Each FMGC monitors the validity of the radio altimeter data delivered by each bus (refresh, status matrix validity).
This monitoring selects the appropriate bus and causes disengagement of the AP/FD in case of total loss of the two radio altimeters at LAND ARM mode selection or at GLIDE CAPTURE or GLIDE TRACK or LAND TRACK mode selection.

Monitoring of the runway heading delivered by the ILS (refresh and status matrix validity)
Deviation between runway heading and magnetic track delivered by the ADIRS less than 7 deg. between 700 ft and 100 ft.

These functions are effective as soon as the LAND Mode is selected.

(d) ILS monitoring
Each FMGC monitors the parameters transmitted by both ILS/MMR receivers.
Total loss of ILS information at LAND ARM or LOC ARM selection results in AP and FD disengagement (except in the event of glide deviation loss below 100 ft.).

(e) Validities of lateral and longitudinal flight plans
The AP/FD is disengaged when the validity of lateral or longitudinal flight plan is lost, with FINAL DES mode armed or active.

(f) FCU parameter monitoring
This monitoring takes into account the validity of the FCU bus data (refresh and status matrix). It is inhibited in LAND TRACK or GO AROUND mode.

(4) AP/FD/A THR Common Conditions

AP/FD/A THR Common Conditions

This logic covers all the conditions common to the AP, FD and A/THR functions.

(a) Monitoring of ADIRS parameters
Two types of monitoring functions performed on the ADR and IR labels.

1 For all the data
Status matrix and refresh monitoring (failure detected by self-test) through the peripheral).

2 For some important data

comparison of the data from the 3 ADIRS
2 by 2 comparison of with respect to the voted value (failure not detected by self-test through the peripheral).

At first failure (detected by self-test or not) the considered FMGC can change over automatically on the ADIRS 3 data (manual switching can also be performed on the panel 8VU).
A second failure causes disengagement of the AP, FD and A/THR systems.

(b) Validity of the FM part
This validity which is necessary to engage the cruise modes, is no longer taken into account in the following modes : G/S TRACK below 700 ft., LAND TRACK and GO AROUND.

(c) Landing-gear data availability
The FAC delivers the information related to landing-gear data availability.
This item of information is not taken into account in LAND and GO AROUND modes.

(5) FD Command Generation

FD Basic Loops

The following basic loops generate the FD commands:

(a) FD pitch control command
This command is generated from the outer loop command - DELTA THETA C FD.
The bar control command takes into account data feedback. It is limited to plus or minus 22.5 deg.
A vertical acceleration term is added when the commands are displayed in FPV mode (flight path vector).

(b) FD roll control command
This command is generated from the outer loop command - PHI C.
When the FD commands are presented by crossed bars, the roll FD command is limited to plus or minus 45 deg..

(c) FD yaw control command
This command is displayed on the PFDs in these phases only: ROLL OUT, RUNWAY (to 30 ft.) and ALIGN (Ref. para 2. A. (6).
The DELTA R YAW command is generated in the yaw AP basic loop. The FD command is limited to plus or minus 45 deg. in amplitude.

(d) FD command monitoring
The FD pitch and yaw control commands are computed in the command and monitoring channels and then compared

FD Command Monitoring

The result of these comparisons is used to generate the FG HEALTHY signal. (Ref. para 2. A. (2) Internal Monitoring Logic)
In TAKE OFF, LANDING and GO AROUND modes, the pitch and yaw outer loop commands are computed in the command and monitoring channels.

(6) Removal of FD Commands

Removal of FD Commands

The FD commands can be removed in two ways:

(a) Removal manual control
The crew can clear the FD commands by means of the FD pushbutton switches located on the FCU.
Action on one FD pushbutton switch results in:

Extinguishing of the FD P/B
Removal of the FD commands (tendency bars or flight path director symbols) on the associated PFD.

A second action on the illuminated pushbutton switch leads to:

Illumination of the P/B (three green bars)
Display of the FD commands.

The FD pushbutton switches come on automatically:

Upon energization
Upon loss of the AP, the ROLL OUT mode being active.

(b) Logic - controlled removal
The FD commands (on the three axes) are delivered to the DMCs on three different labels:

Label 141 PITCH FD BAR
Label 140 ROLL FD BAR
Label 143 YAW FD BAR.

This logic orders the DMCs to clear a command by forcing the status matrix of the corresponding label to NCD:

NCD on the three labels when the FD ENGD condition is lost
NCD on the label 141 when no longitudinal mode is engaged or when the ROLL OUT mode is active
NCD on the label 140 when no lateral mode is engaged or when the RUNWAY LOC or the ROLL OUT modes are active
NCD on the label 143 as long as the RUNWAY LOC, ROLL OUT or ALIGN modes are not active.

(7) FD Display Flashing
The FMGCs can send a command to the DMCs to make the FD bars flash.

(a) FD pitch bar
This bar flashes in the following conditions:

When the transmission of the glide data is interrupted above 100 ft. with the G/S CPT, GS/TRACK and LAND TRACK modes engaged.
If the ALT ACQ mode is lost further to altitude reference change (the bar flashes for 10 s).
If the V/S mode is engaged (further to pilot action or loss of the lateral approach mode) with the G/S CPT, G/S TRACK, LAND TRACK or FINAL DESCENT modes engaged (the bar flashes for 10 s).
When one AP or FD is engaged, when no AP/FD were previously engaged (the bar flashes for 10 s).

(b) FD roll bar
This bar flashes in the following conditions:

When the transmission of the LOC data is interrupted above 15 ft. with the LOC CPT, LOC TRACK and LAND TRACK modes engaged.
If the HDG mode is engaged (further to pilot action or loss of the longitudinal approach mode) with the LOC CPT, LOC TRACK, LAND TRACK modes engaged or in the NAV mode associated with RNAV approach (the bar flashes for 10 s).
When one AP or FD is engaged, when no AP/FD were previously engaged (the bar flashes for 10 s).

B. AP Engagement

(1) General
The AP is engaged through two pushbutton switches (AP1 and AP2) located on the center section of the FCU.
In cruise only one AP can be engaged at a time (priority to the last AP engaged).
Both APs can be engaged when the following modes are active or armed:

LAND mode
GO AROUND mode.

In these cases, the AP1 has priority and is active. The AP2 is in standby and becomes active if the AP1 is lost.
When these modes are released, the AP2 is disengaged automatically.
The AP can be engaged on the ground in any mode with engines stopped.
The AP disengages when one engine is started.
An AP can be engaged again 5 s after lift-off in active FD modes (if at least one FD is engaged) and, in HDG and V/S modes (if no FD is engaged).
At AP engagement, the load thresholds on the side stick controllers and on the rudder pedals are increased.
AP engagement is indicated by the illumination of the corresponding pushbutton switch (three green bars) and by the AP1 or AP2 indication in the status column on the PFDs.
The pilot can disengage the AP in different ways:

By action on the engagement pushbutton switch, with the green bars on.
By action on one takeover and priority pushbutton switch on the side stick controller.

Loss of the AP is indicated by an aural and visual warning (Ref. para. 2. B. (6).

(2) AP ENGD Hardware Logic

AP - Engage Hardware Logic

(a) Principle
A part of the AP engage logic is accomplished through the hardware. It takes into account the following signals:

AP ENGD boolean generated in the software
FG HEALTHY logic signal (Ref. para 2. A. (2))
AP SW wired discrete from the FCU.

The AP ENGD hardware logic utilizes the command and the monitoring channels. Each output discrete takes into account the conditions generated by each generated by each channel.
During the safety tests (at power rise) the AP SW signal is inhibited prohibiting engagement through the pushbutton switch.
The disengagement takes place in the hardware logic:

Upon loss of one of the AP ENGD and FG HEALTHY signals after confirmation of 200 ms.
Through action on one takeover and priority pushbutton switch located on the side stick controllers.
Upon detection of long power failure (LPF) by the power unit.

In the event of short interruption, the engage signal maintains its pre-cutoff state. The final circuits are therefore supplied with back-up current (VS).
They are isolated from the other signals during the cutoff (SW RESET signal active).

The AP ENGD wired discretes obtained are used by : the FACs (selection of AUTO mode and acquisition of yaw axis guidance signals)
The ELACs (selection of AUTO mode and acquisition of guidance signals, pitch and roll axes and nose-wheel steering)
The FCU (illumination of the corresponding AP pushbutton switch, 3 green bars, and selection of the FMGCs (generation of the AP warning)
The opposite FMGC (disengagement of associated AP if in cruise modes, selection of the FMGC having priority)
The OWN FMGC (engagement wrap around).

(b) AP ENGD Software Logic

1 Engagement conditions
This signal is at 1 (flip-flop set) if all the engagement conditions are activated:

Action on the engagement pushbutton switch
Ground conditions : engagement possible in any mode only if the engines are shut down
Flight conditions : engagement possible 5 s after lift-off
Conditions specific to the AP : AP COND (Ref. para. 2. B. (5)
Conditions common to the AP/FD : AP/FD COND (Ref. para. 2. A. (3)
Conditions common to the AP/FD and A/THR : AP/FD/A THR COND (Ref. para. 2. A. (4).

2 Disengagement conditions
This signal is set to O (flip-flop reset) when a disengagement condition is present:

Action on the engagement pushbutton switch, the associated AP being already engaged
Engagement of the opposite AP if the AP is not in LAND or GO AROUND mode
Action on one takeover and priority pushbutton switch
One engine start on the ground
Loss of one condition : either AP COND, or AP/FD COND or AP/FD/ A-THR COND
In the event of landing in dual-AP operation, disengagement of AP2 only when the LAND or GO AROUND mode is released.

(3) AP Specific Conditions (AP COND)

AP COND Logic

This logic covers all the conditions required to engage the AP

(a) Feedback of wired engage discretes
Engagement is confirmed by the feedback of four AP ENGD discretes delivered by each FMGC.
Therefore for the FMGC1:

The AP ENGAGEMENT FEEDBACK condition (command) is set to 0 upon loss of discrete AP1 ENGD1 or 2 delivered by the command channel
The AP ENGAGEMENT FEEDBACK condition (monitor) is set to 0 upon loss of discrete AP1 ENGD3 or 4 delivered by the monitoring channel.

(b) Disengagement through AP takeover and priority pushbutton switches

1 FAC

Availability of at least one FAC (CMD and MON FAC HEALTHY wired discretes).
Confirmation of FAC operation in AUTO mode further to AP engagement by the FAC
Engagement of the yaw damper function
Engagement of the rudder trim function.

Loss of one of the above five logic conditions is not taken into account in LAND TRACK, between 100 ft. and the ground.

2 ELAC
Each ELAC generates ELAC AP DISC discretes.
The AP disengages only upon a command from the two ELACs.
The disconnection command from only one ELAC results in a reduction of landing capability.

(d) Condition specific to GO AROUND and TAKEOFF modes
On the ground, the engagement of the GO AROUND mode or positioning of the both throttle control levers in or above the MCT/FLX gate result in AP disengagement.

(4) Generation of AP Commands

(a) Pitch basic loop

Pitch Basic Loop ** ON A/C NOT FOR ALL

When the AP is engaged, the delta q command generated in the pitch basic loop is sent to the ELAC and controls the power loop of the elevator servocontrols. The delta q command integrated in the ELAC is then fed to the THS actuator for the autotrim function.
The delta q command is limited in amplitude (-18 deg., +9 deg.) and in variation speed (10 deg./s in clean configuration, 20 deg./s with flaps and slats extended).
Two inputs are applied to the pitch basic loop:

A cruise input
A landing input which optimizes performances but requires higher response for the elevator servocontrols.

Change from one input to the other occurs at selection of the G/S GPT mode.

1 Cruise
The delta q elevator command is generated from:

The outer loop command - delta theta c AP
The aircraft feedbacks in pitch angle (theta), pitch attitude rate and roll angle (phi).

In certain modes (ALT, V/S, FPA) an engine torque compensation is added to the term -delta theta c AP to minimize the path deviations due to important thrust variations. Use of the CG position permits to improve stability when the aircraft is in nose-heavy condition.

2 Landing
The delta q elevator command is generated from:

The outer loop command - delta n Z c
The aircraft feedbacks : vertical acceleration, pitch angle, pitch attitude rate and roll angle.

(b) Roll basic loop

Roll Basic Loop ** ON A/C NOT FOR ALL

Two deflection commands for the various roll control surfaces are fed from the basic loop:

A delta p aileron command is sent to the ELACs
A delta p spoiler command is sent to the SECs via the ELACs.

In addition, the aileron delta p command is used by the FACs for turn coordination and rudder trim.
The aileron and spoiler delta p commands are generated from the outer loop command -phi c and aircraft feedbacks.
At the output of the inner loop, a gain K (0 in approach, 1 in cruise) permits to switch from a cruise inner loop to an approach inner loop.
These deflection orders are limited in amplitude and in variation speed as follows:

delta p aileron LIM plus or minus 25 deg.

RLIM 25 deg./s

delta p spoiler LIM plus or minus 35 deg.

RLIM 25 deg./s

Upon real or simulated engine failure, the lateral attitude is limited on the -phi c command at the input of the basic loop:

In takeoff phase, the lateral attitude is limited to 15 deg. as long as speed is lower than the maneuvering speed of the clean configuration (Green dot).
In landing phase, and on condition that LOC CPT has not been selected, the lateral attitude is limited to 15 deg. as long as speed is lower than the maneuvering speed of the flaps/slats configuration.

Yaw Basic Loop ** ON A/C NOT FOR ALL

The delta r command of the yaw basic loop is computed by the FMGC in the approach phase only. In the other cases, the basic loop is computed in the FACs.
This command is then fed to the FACs to control the yaw power loop.
In addition, the delta r command is integrated in the FAC and transmitted to the rudder trim actuator.
This order is limited in amplitude (plus or minus 20 deg.) and in variation speed (30 deg./sec) in clean configuration.
In approach phase (from LOC CPT to ALIGN) the delta r command is generated from the outer loop command-phi c and aircraft feedbacks.
In roll out phase, the delta r command is generated from the delta r ROLL OUT signals computed in the LOC laws.
In this phase the FMGC also generates a nosewheel steering command (delta NOSEWHEEL) for the BSCU. This command is limited in amplitude (plus or minus 6 deg.) and in variation speed (5 deg./s).

(d) Deflection command consolidation

AP Command Generation ** ON A/C NOT FOR ALL

The basic loop is computed for each axis in the command and monitoring channels.
The peripherals use the deflection commands resulting from the vote performed on the commands delivered by each channel. The vote is made taking into account the smallest value (absolute value).
Comparators permit to detect:

Differences between each input and output of voter
Differences between the outputs of voters.

The result of these comparisons is taken into account in the generation of the FG HEALTHY signal.
In TAKE OFF, LANDING and GO AROUND modes, the outer loop commands are computed separately by the command and monitoring channels. This duplicates the generation of deflection commands in these modes.
In cruise modes, the outer loop commands are limited in amplitude and in speed in the basic loops. In cruise, this limits the effects of failures affecting the outer loop commands.

(5) Generation of AP Commands

(a) Pitch basic loop

Pitch Basic Loop ** ON A/C NOT FOR ALL

A cruise input
A landing input which optimizes performances but requires higher response for the elevator servocontrols.

Change from one input to the other occurs at selection of the G/S GPT mode.

1 Cruise
The delta q elevator command is generated from:

The outer loop command - delta theta c AP
The aircraft feedbacks in pitch angle (theta), pitch attitude rate and roll angle (phi).

2 Landing
The delta q elevator command is generated from:

The outer loop command - delta n Z c
The aircraft feedbacks : vertical acceleration, pitch angle, pitch attitude rate and roll angle.

(b) Roll basic loop

Roll Basic Loop ** ON A/C NOT FOR ALL

Two deflection commands for the various roll control surfaces are fed from the basic loop:

A delta p aileron command is sent to the ELACs
A delta p spoiler command is sent to the SECs via the ELACs.

delta p aileron LIM plus or minus 25 deg.

RLIM 25 deg./s

delta p spoiler LIM plus or minus 35 deg.

RLIM 25 deg./s

Upon real or simulated engine failure, the lateral attitude is limited on the -phi c command at the input of the basic loop:

In takeoff phase, the lateral attitude is limited to 15 deg. as long as speed is lower than the maneuvering speed of the clean configuration (Green dot).
In landing phase, and on condition that LOC CPT has not been selected, the lateral attitude is limited to 15 deg. as long as speed is lower than the maneuvering speed of the flaps/slats configuration.

Yaw Basic Loop ** ON A/C NOT FOR ALL

The delta r command of the yaw basic loop is computed by the FMGC in the approach phase only. In the other cases, the basic loop is computed in the FACs.
This command is then fed to the FACs to control the yaw power loop.
In addition, the delta r command is integrated in the FAC and transmitted to the rudder trim actuator.
This order is limited in amplitude (plus or minus 20 deg.) and in variation speed (15 deg./sec) in clean configuration.
In approach phase (from LOC CPT to ALIGN) the delta r command is generated from the outer loop command-phi c and aircraft feedbacks.
In roll out phase, the delta r command is generated from the delta r ROLL OUT signals computed in the LOC laws.
In this phase the FMGC also generates a nosewheel steering command (delta NOSEWHEEL) for the BSCU. This command is limited in amplitude (plus or minus 6 deg.) and in variation speed (5 deg./s).

(d) Deflection command consolidation

AP Command Generation ** ON A/C NOT FOR ALL

Differences between each input and output of voter
Differences between the outputs of voters.

(6) Increase of Load Thresholds on Side Stick Controllers and Rudder Pedals

Side Stick Controllers and Rudder Pedals - Locking Logic

When the AP is engaged, the command and the monitoring channels supply the relays which control the pitch and roll lock solenoids (the command channel provides the +28V, the monitoring channel provides the ground).
Each control has its own solenoid.
Each AP has its own relays and can therefore lock the controls.

(a) Side stick controllers
The loads are increased on both axes.
The pitch load threshold changes from 0.5 daN to 5 daN. The roll load threshold changes from 0.5 daN to 3.5 daN.
Any load on the side stick controller which exceeds these values, results in AP disconnection (wired discrete from the ELACs, Ref. 22-10-00).

(b) Rudder pedals
The load is applied on the rudder artificial feel (addition of a spring in the artificial feel and trim unit).
The load threshold changes from 10 to 30 daN when the AP is engaged.

NOTE: Exceeded load results in AP disconnection.

(7) Warnings

(a) AP OFF warning

AP OFF Warning

The FWCs generate various warnings upon AP disengagement.
Their display and the clearing actions depend on the origin of the disengagement.

1 Manual disengagement through takeover and priority pushbutton switches
Upon disengagement through these pushbutton switches, the FWCs generate the following warnings:

The red MASTER WARN lights on the glareshield flash for 3 s
The red AP OFF message is displayed for 9 s on the upper display unit of the ECAM system in the MEMO section
The cavalry charge aural warning sounds for 1.5 s.

All these warnings are cleared automatically. Action on one takeover and priority pushbutton switch or on the one MASTER WARN light enables to cancel these warnings. The crew can also clear the AP OFF message on the display unit of the ECAM system (minimum duration of the aural warning is 0.5 s).

2 Disengagement resulting from a failure or from the pilot pushing the FCU AP pushbutton, or from a force on the sidestick or rudder pedals
The FWCs generate the following warnings:

The red MASTER WARN lights flash
The red AUTO FLT AP OFF message is displayed on the upper display unit of the ECAM system
The cavalry charge aural warning sounds
The CLR pushbutton switch on the ECAM control panel comes on.

These warnings are not cancelled automatically:

Action on one takeover and priority pushbutton switch or on one MASTER WARN light cancels this warning and the cavalry charge warning stops after 1.5 s
Action on the CLR pushbutton switch cancels all the AP warnings (MASTER WARN light, message on the upper display unit of the ECAM system and aural warning).
This action enables the display of the STATUS page (AP1 or AP2 or AP1 + 2) on the lower display unit of the ECAM system.

NOTE: At AP disengagement, and in addition to these warnings the corresponding engagement pushbutton switch on the FCU goes off.
The AP1 or AP2 or the AP1 + 2 message disappears in the engagement status column of the FMA on the PFD(s).

(b) AP availability
The FMGC generates an AP INOP message to the FWCs giving the availability of the associated AP. When this item of information is present, the AP1 or/and AP2 message is displayed in the INOP SYS column of the lower display unit of the ECAM system.
Each FMGC takes into account the following items of information for the availability of the AP:

Its own validity and the validity of the FM part
ADR validity
IR validity
FCU validity
Rudder trim availability
Yaw damper availability
FAC and characteristic speed validity
LGCIU validity
ELAC availability.

[Rev.10 from 2021] 2026.03.31 23:09:57 UTC