DOC AIRBUS | AMM A320FARTIFICIAL FEEL AND RUDDER TRAVEL LIMITING COMPUTATION - DESCRIPTION AND OPERATION
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1. General
The rudder travel-limiting function provides:
** ON A/C NOT FOR ALL The rudder travel-limiting function provides:
- The limitation of the rudder travel through a control law function of Vc
- The return to the low speed limitation in case of failure
The rudder travel limiting actuation is described in 27-23-00.
2. System Description
A. Composition
The system consists of:
The system consists of:
- Two engagement pushbutton switches common to the yaw damper and rudder trim functions
- Two Flight Augmentation Computers (FAC 1 and FAC 2)
- An electro-mechanical rudder travel-limitation unit with two motors
- Two position transducers integrated in the unit.
B. Architecture
The rudder travel-limiting system operates using the changeover technique i.e when both sides are engaged the side 1 has priority, the side 2 is in standby. The side 2 is active when the side 1 is disengaged (case of failure). The motor of the standby side is not supplied (the FAC which has no priority does not deliver the enable signal).
A synchronization is achieved on the rudder position prior to engagement
Amplitude and speed limitations are introduced:
The rudder travel-limiting system operates using the changeover technique i.e when both sides are engaged the side 1 has priority, the side 2 is in standby. The side 2 is active when the side 1 is disengaged (case of failure). The motor of the standby side is not supplied (the FAC which has no priority does not deliver the enable signal).
A synchronization is achieved on the rudder position prior to engagement
Amplitude and speed limitations are introduced:
- The amplitude limitation is such that the travel remains compatible with the limits on the aircraft structure
- The speed limitation prevents saturation of the limitation unit.
Upon total loss of the rudder travel-limiting function, a control enables to bring back the stops to the low speed conditions to restore maximum rudder deflection as soon as slats are extended.
3. Power Supply
A. Power Supply of the Rudder Travel-Limitation Unit
The 26 V/400 Hz power is applied to the primary windings of the position transducers directly from the busbars via the FAC circuit breakers.
The emergency control of the motor operates on the same power supply.
The 28VDC power is applied to the power electronic set from the FAC circuit breakers through a cut-off relay. This relay is controlled by the monitoring logic of the FAC.
The 26 V/400 Hz power is applied to the primary windings of the position transducers directly from the busbars via the FAC circuit breakers.
The emergency control of the motor operates on the same power supply.
The 28VDC power is applied to the power electronic set from the FAC circuit breakers through a cut-off relay. This relay is controlled by the monitoring logic of the FAC.
4. Interface
A. Interface Signals
For each side:
For each side:
(1) Control signal (2 wires)
The control order signal is transmitted through a two-wire twisted lead (high point and low point).
The control order signal is transmitted through a two-wire twisted lead (high point and low point).
(2) Position transducer signal (4 wires)
Two voltages : V1 and V2 (2 wires each).
Two voltages : V1 and V2 (2 wires each).
(3) Enable signal (1 wire)
This signal is transmitted by the FAC control logic and controls the coil of a relay inside the rudder travel-limitation unit (+28VDC = motor activated ; open circuit = motor not activated).
This signal is transmitted by the FAC control logic and controls the coil of a relay inside the rudder travel-limitation unit (+28VDC = motor activated ; open circuit = motor not activated).
(4) Return to low speed signal (2 wires)
This signal controls the coil of a relay inside the rudder travel-limitation unit.
+28VDC = return to low speed order (delivered by the FAC control logic command).
Ground = return to low speed order (delivered by the FAC control logics monitor)
The FAC provides the coil with the electrical ground.
This signal controls the coil of a relay inside the rudder travel-limitation unit.
+28VDC = return to low speed order (delivered by the FAC control logic command).
Ground = return to low speed order (delivered by the FAC control logics monitor)
The FAC provides the coil with the electrical ground.
(5) Monitoring signal (1 wire)
This signal which is transmitted by the rudder travel-limitation unit to the FAC is used during the test procedure of the rudder travel-limitation unit:
Ground = rudder travel-limitation unit declared good.
Open circuit = rudder travel-limitation unit failed.
This signal which is transmitted by the rudder travel-limitation unit to the FAC is used during the test procedure of the rudder travel-limitation unit:
Ground = rudder travel-limitation unit declared good.
Open circuit = rudder travel-limitation unit failed.
5. Operation
(1) Normal operation
The active system controls the limitation unit through its motor.
It limits the rudder travel according to a parameter specific to the flight envelope ie the corrected airspeed (VC).
This parameter which is delivered by the ADIRS (Air Data/Inertial Reference System) is monitored by the FAC (Ref. AMM D/O 22-65-00-00).
Each motor has its own power electronic set. A FAC logic interrupts the power of the electronic set on the side which is not active and thus de-activates the associated motor (Ref. para. C).
Two position transducers enable slaving and monitoring of the channel.
The active system controls the limitation unit through its motor.
It limits the rudder travel according to a parameter specific to the flight envelope ie the corrected airspeed (VC).
This parameter which is delivered by the ADIRS (Air Data/Inertial Reference System) is monitored by the FAC (Ref. AMM D/O 22-65-00-00).
Each motor has its own power electronic set. A FAC logic interrupts the power of the electronic set on the side which is not active and thus de-activates the associated motor (Ref. para. C).
Two position transducers enable slaving and monitoring of the channel.
(2) Return to low speed conditions
This mode, which is the emergency mode, serves in case of failure of the FAC or of the power electronic set (when the failure prevents the normal operation of the rudder travel-limitation unit). This mode which is independent from the normal control, is only initiated at low speed (in slats extended configuration).
A FAC internal logic (Ref. para. C) controls a relay which switches the limitation unit to a control order called emergency control order (independent 26 V/400 Hz power supply).
This mode, which is the emergency mode, serves in case of failure of the FAC or of the power electronic set (when the failure prevents the normal operation of the rudder travel-limitation unit). This mode which is independent from the normal control, is only initiated at low speed (in slats extended configuration).
A FAC internal logic (Ref. para. C) controls a relay which switches the limitation unit to a control order called emergency control order (independent 26 V/400 Hz power supply).
B. Structure of the Control Law
Rudder Travel-Limitation Unit - Control Law ** ON A/C NOT FOR ALL
Rudder Travel-Limitation Unit - Control Law ** ON A/C NOT FOR ALL
Rudder Travel-Limitation Unit - Control Law ** ON A/C NOT FOR ALL
The control law generates a deflection order.
A synchronization is achieved for the channel in standby mode or not engaged, from the position of the motor position feedback.
Rudder Travel-Limitation Unit - Control Law ** ON A/C NOT FOR ALL Rudder Travel-Limitation Unit - Control Law ** ON A/C NOT FOR ALL Rudder Travel-Limitation Unit - Control Law ** ON A/C NOT FOR ALL A synchronization is achieved for the channel in standby mode or not engaged, from the position of the motor position feedback.
C. Operating Logic
(1) Normal operation
The rudder travel-limitating system operates using the changeover technique when a channel is detected faulty. The priority is given to the side 1 through the aircraft wiring (side 1 signal).
In normal operation the RTL (Rudder Travel-Limiting) channel No. 1 is active and drives the associated motor.
The other channel is in standby (synchronization mode) and the power electronic set of the associated motor is not supplied.
This changeover is accomplished through hard-wired logic as follows:
The rudder travel-limitating system operates using the changeover technique when a channel is detected faulty. The priority is given to the side 1 through the aircraft wiring (side 1 signal).
In normal operation the RTL (Rudder Travel-Limiting) channel No. 1 is active and drives the associated motor.
The other channel is in standby (synchronization mode) and the power electronic set of the associated motor is not supplied.
This changeover is accomplished through hard-wired logic as follows:
- A logic signal C (+28VDC = motor activated) controls a relay inside the motor
- A logic signal M (+28VDC = motor activated) controls an intermediary relay 13CC1(2) which supplies (+28VDC via the circuit breaker 5CC1 (2)) the power electronic set of the associated servomotor.
- The hard-wired signal on side 1
- The hard-wired signal of the active opposite RTL function
- The general monitoring of the FAC
- The RTL specific logic.
This logic validates the associated power channel according to the considered side.
(2) Return to low speed logic
This logic controls the motor in emergency mode when the normal control is not possible (FAC or motor electronic failure).
It controls a relay inside the rudder travel-limitation unit.
This relay switches the motor on a supply independent from the power electronic set of the limitation unit. This supply is delivered from the 26VAC busbar through the circuit breaker 14CC1(2).
The switching relay is activated upon slat extension:
The FAC provides the relay ground (signal M) from the monitoring side.
The logic is identical for both sides.
This logic controls the motor in emergency mode when the normal control is not possible (FAC or motor electronic failure).
It controls a relay inside the rudder travel-limitation unit.
This relay switches the motor on a supply independent from the power electronic set of the limitation unit. This supply is delivered from the 26VAC busbar through the circuit breaker 14CC1(2).
The switching relay is activated upon slat extension:
- In case of dual failure of the rudder travel-limitation function, and
- During a fixed time corresponding to the acquisition of the maximum stop.
The FAC provides the relay ground (signal M) from the monitoring side.
The logic is identical for both sides.
D. Monitoring of Rudder Travel-Limiting Function
This function has three types of monitoring.
This function has three types of monitoring.
(1) Monitoring of acquisition
The VC parameters from the ADIRS are monitored by a two-by-two comparison (Ref. 22-65-00).
The VC parameters from the ADIRS are monitored by a two-by-two comparison (Ref. 22-65-00).
(2) Monitoring of computation
After amplitude and speed limiting, the C and M computation orders are compared (C and M duplicated C1 comparators).
Activation of this monitoring function causes the loss of the rudder travel limiting function on the considered side.
After amplitude and speed limiting, the C and M computation orders are compared (C and M duplicated C1 comparators).
Activation of this monitoring function causes the loss of the rudder travel limiting function on the considered side.
(3) Power monitoring
Two position transducers are used for slaving and monitoring.
This monitoring is based on:
Two position transducers are used for slaving and monitoring.
This monitoring is based on:
- The monitoring of the acquisition of the transducer (cut wire, short circuits, variation of the power supply voltage)
- A comparator C2 between the order and the rudder feedback on the sides C and M.
(4) Warnings
The loss of the rudder travel-limiting function is indicated by the warnings given below:
The loss of the rudder travel-limiting function is indicated by the warnings given below:
(a) Loss of a rudder travel-limiting channel
The amber message: AUTO FLT RUD TRV LIM 1(2) appears on the upper display unit of the ECAM system.
The amber message: AUTO FLT RUD TRV LIM 1(2) appears on the upper display unit of the ECAM system.
(b) Loss of two rudder travel-limiting channels
The amber message: AUTO FLT RUD TRV LIM SYS appears on the upper display unit of the ECAM system and the single chime sounds.
After action on the CLR pushbutton switch on the ECAM control panel this message appears: SYSTEM INOP : RUD TRV LIM.
The RTL indication on the FLT CTL page of the ECAM system is flagged (amber indexes) if this information is not available.
The amber message: AUTO FLT RUD TRV LIM SYS appears on the upper display unit of the ECAM system and the single chime sounds.
After action on the CLR pushbutton switch on the ECAM control panel this message appears: SYSTEM INOP : RUD TRV LIM.
The RTL indication on the FLT CTL page of the ECAM system is flagged (amber indexes) if this information is not available.
6. Test Procedure
A. Test of Rudder Travel-Limitation Unit
A test procedure is initiated at FAC energization to check the integrity of the standby channel.
This procedure permits to check:
A test procedure is initiated at FAC energization to check the integrity of the standby channel.
This procedure permits to check:
- The triggering capability of the internal monitoring of the rudder travel-limitation unit
- The slaving of the rudder travel-limitation unit without motion of the rudder.
(1) Monitoring triggered at fault status
The enable order is not sent : the motor order is fed back on the test circuit of the rudder travel-limitation unit.
A null order lower than the programmed threshold is sent and the monitoring must be triggered (open circuit to the FAC).
The enable order is not sent : the motor order is fed back on the test circuit of the rudder travel-limitation unit.
A null order lower than the programmed threshold is sent and the monitoring must be triggered (open circuit to the FAC).
(2) Monitoring triggered at good status
The enable order is not sent.
The rudder travel-limitation unit receives a slaving order (equal to half of the travel) and the monitoring must return to good status (ground to the FAC).
The enable order is not sent.
The rudder travel-limitation unit receives a slaving order (equal to half of the travel) and the monitoring must return to good status (ground to the FAC).
(3) Test of slaving
The enable order is sent as well as a null order. The stage of the switching relay of the enable order must be tested. The monitoring must be forced to the good status.
The enable order is sent as well as a null order. The stage of the switching relay of the enable order must be tested. The monitoring must be forced to the good status.
B. Test of Return to Low Speed Function
The test of the return to low speed function is not automatic. It can be performed on the ground by maintenance personnel in the conditions given below:
The test of the return to low speed function is not automatic. It can be performed on the ground by maintenance personnel in the conditions given below:
- FAC 1 and FAC 2 pushbutton switches set to OFF
- Slats extended.
C. Test of Cutoff Relays
The test of the RTL SYS1 and SYS2 relays 13CC1 and 13CC2 (cutoff of the 28 V of the rudder travel-limitation unit) is performed automatically during these tests (capability to open).
The test of the RTL SYS1 and SYS2 relays 13CC1 and 13CC2 (cutoff of the 28 V of the rudder travel-limitation unit) is performed automatically during these tests (capability to open).