DOC AIRBUS | AMM A320FAUTOTHRUST - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
1. General
The autothrust (A/THR) system is part of the auto flight system (Ref. 22-00-00 AUTO FLIGHT - GENERAL).
The autothrust system ensures the functions below through the control of the thrust:
The Engine Interface Units (EIUs) and the Electronic Control Units (ECUs)/ Electronic Engine Control (EECs) ensure the link between this system and the engines.
The use of digital engine control units simplify the autothrust system through:
** ON A/C NOT FOR ALL The autothrust (A/THR) system is part of the auto flight system (Ref. 22-00-00 AUTO FLIGHT - GENERAL).
The autothrust system ensures the functions below through the control of the thrust:
- speed hold (pilot selection i.e. manual control or FMS computed i.e. auto control)
- Mach hold (pilot selection i.e. manual control or FMS computed i.e. auto control)
- thrust hold
- thrust reduction during flare-out (RETARD)
- protection against excessive angle of attack (ALPHA FLOOR function).
The Engine Interface Units (EIUs) and the Electronic Control Units (ECUs)/ Electronic Engine Control (EECs) ensure the link between this system and the engines.
The use of digital engine control units simplify the autothrust system through:
- the deletion of the autothrottle actuator (use of a digital link between the FMGC and the ECUs/EECs)
- the deletion of the limit thrust computation (already performed by the ECUs/EECs)
- the deletion of the limit thrust panel (the ECUs/EECs make this selection automatically depending on the position of the throttle control levers)
- the deletion of the TO/GA levers (the engagement of these modes is made through push action on the throttle control levers).
2. Component Location
** ON A/C NOT FOR ALL 
Cockpit - Location of Controls and Indications| FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C ALL | |||||
| 1CA1 | FMGC-1 | 824 | 127 | 22-83-34 | |
| 1CA2 | FMGC-2 | 84VU | 128 | 22-83-34 | |
| 2CA | FCU | 13VU | 210 | 22-81-12 | |
| 3CA1 | MCDU-1 | 11VU | 210 | 22-82-12 | |
| 3CA2 | MCDU-2 | 11VU | 210 | 22-82-12 | |
| 7CA1 | P/BSW-A/THR INST DISC, CAPT | 211VU | 210 | 22-31-00 | |
| 7CA2 | P/BSW-A/THR INST DISC, F/O | 210VU | 210 | 22-31-00 | |
| 1CC1 | FAC-1 | 83VU | 127 | 22-66-34 | |
| 1CC2 | FAC-2 | 84VU | 128 | 22-66-34 | |
| 1KS1 | EIU-1 | 85VU | 127 | 73-25-34 | |
| 1KS2 | EIU-2 | 86VU | 128 | 73-25-34 | |
3. System Description
(1) Manual thrust control
In this mode, the thrust is dependent on the position of the throttle control levers.
In this mode, the thrust is dependent on the position of the throttle control levers.
1 The throttle control levers move over a sector divided into three separate sections:
- rear section : application of reverse thrust
- center section : normal throttle control levers displacement in flight from idle to max. climb (CL) thrust. The forward position of this section corresponds to the selection of the CL thrust limit (gate).
- forward section : it has two mechanical devices which allow to select thrust limit modes below MCT/FLX TO (gate) and TO/GA (stop).
2 Each ECU/EEC (one per engine) associates a thrust (N1/EPR CMD) with the position of the corresponding throttle control lever.
(b) Selection of the limit thrust modes
1 Principle
The selection of the limit thrust modes (CL, MCT, FLX TO, TO/GA) is made when the throttle control levers are placed in one of the gates (or stops) below:
The selection of the limit thrust modes (CL, MCT, FLX TO, TO/GA) is made when the throttle control levers are placed in one of the gates (or stops) below:
- CL (gate)
- MCT/FLX TO (gate)
- TO/GA (stop).
2 Initialization on the ground
On the ground, with engines stopped, the computation of the limit thrust is initialized on the mode which corresponds to the position of the throttle control levers.
On the ground, with engines running, the computation of the limit thrust is made in the TO/GA mode.
On the ground, with engines stopped, the computation of the limit thrust is initialized on the mode which corresponds to the position of the throttle control levers.
On the ground, with engines running, the computation of the limit thrust is made in the TO/GA mode.
3 Specific case of FLX TO mode - FLX TO/MCT switching
As the gates for the FLX TO/MCT modes correspond to a same position, a specific logic has been adopted for the selection of these modes:
As the gates for the FLX TO/MCT modes correspond to a same position, a specific logic has been adopted for the selection of these modes:
- On the ground
If a fictitious temperature (FLX TO temperature) higher than the TAT is entered on the MCDU (TAKEOFF page), the limit thrust computation is made in FLX TO mode.
The fictitious temperature is shown on the ECAM display unit together with the engine parameters as long as the FLX TO mode is engaged.
For safety reasons, the fictitious temperature is frozen at takeoff as soon as a throttle control lever reaches the CL position. - In flight
The FLX TO-to-MCT switching is made when the throttle control levers are moved from the FLX TO/MCT position to another position (TO/GA or CL) and returned to the FLX TO/MCT position.
(2) Autothrust control
In this mode, the thrust is computed by the autothrust (A/THR) system.
The A/THR function engaged can be:
In this mode, the thrust is computed by the autothrust (A/THR) system.
The A/THR function engaged can be:
(a) Active
Two cases are considered:
Two cases are considered:
1 Case 1 : Alpha floor protection inactive:
With the two throttle control levers between IDLE and CL, the engines are controlled by the A/THR function. However, the ECU/EEC limits the control of each engine to a max. rate depending on the position of the throttle control lever.
With the two throttle control levers between IDLE and CL, the engines are controlled by the A/THR function. However, the ECU/EEC limits the control of each engine to a max. rate depending on the position of the throttle control lever.
NOTE: When the A/THR function is engaged, the normal position of the throttle control levers is the CL gate (two-engine operation) or the MCT gate (in the event of an engine failure).
The throttle control levers shall be positioned outside the gates only if the pilot wishes to limit the max. thrust.
The throttle control levers shall be positioned outside the gates only if the pilot wishes to limit the max. thrust.
2 Case 2 : Alpha floor protection active
The A/THR-controlled thrust is equal to the TO/GA thrust for any control lever position.
For safety reasons, each ECU/EEC gives a low limit to the controlled thrust, according to the rate which corresponds to the position of the throttle control lever.
The A/THR-controlled thrust is equal to the TO/GA thrust for any control lever position.
For safety reasons, each ECU/EEC gives a low limit to the controlled thrust, according to the rate which corresponds to the position of the throttle control lever.
(b) Not active
As soon as one throttle control lever is placed outside the IDLE-MCT zone, the two engines are controlled by the position of the throttle control levers.
This lasts as long as the Alpha floor protection is not activated and if at least one throttle control lever stays beyond the IDLE-MCT zone.
As soon as one throttle control lever is placed outside the IDLE-MCT zone, the two engines are controlled by the position of the throttle control levers.
This lasts as long as the Alpha floor protection is not activated and if at least one throttle control lever stays beyond the IDLE-MCT zone.
(3) Memothrust control
In this mode, the thrust is frozen at the loss of the autothrust control.
Upon the disengagement of the A/THR function (which occurs in its active phase), the thrust is frozen for the engines on which the associated throttle control lever is in the CL or MCT gate.
In this mode, the thrust is frozen at the loss of the autothrust control.
Upon the disengagement of the A/THR function (which occurs in its active phase), the thrust is frozen for the engines on which the associated throttle control lever is in the CL or MCT gate.
NOTE: If a throttle control lever is not in one of the CL or MCT gates, there is a return to the manual thrust control on the corresponding engine.
The controlled thrust of each engine becomes again dependent on the position of the throttle control lever as soon as the associated lever is outside the CL or MCT gates.