5. Close-up
________
Subtask 22-62-21-860-050
A. Put the aircraft back to its initial configuration.
(1)
Remove the warning notice(s).
(2)
Make sure that the work area is clean and clear of tool(s) and other items.
1EFF : ALL 1 22-62-21Page 408 1 1 Feb 01/98 1 1 1CES 1 YAW DAMPER COMPUTATION - DESCRIPTION AND OPERATION
__________________________________________________
1. General_______ (Ref. Fig. 001) The yaw damper function ensures:
-
In manual control, the accomplishment of the yaw orders from the elevator aileron computer (ELAC) (stabilization and manual turn coordination). It also provides a yaw-damping degraded law in the event of ELAC failure (alternate law).
-
In automatic control, the accomplishment of the autopilot orders from the Flight Management and Guidance Computer (FMGC) for turn coordination and guidance (align and roll out). It also ensures, in automatic flight, assistance in engine failure recovery and yaw stability. The yaw damper actuation is described in 27-26-00.
2. System Description__________________
A. Composition
The system consists of:
-
Two electro-hydraulic servo-actuators (1 per FAC) centered to the neutral position by an external spring device. Each servo-actuator includes a feedback position transducer (Linear Variable Differential Transducer: LVDT)
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Two Flight Augmentation Computers (FAC 1 and FAC 2)
-A feedback position transducer unit located on the output shaft common to both servo-actuators (Two Rotary Variable Differential Transducers: RVDT)
-Two FLT CTL/FAC pushbutton switches common to the RUD TRIM and RTL functions (for FAC engagement).
B. Architecture (Ref. Fig. 002) All the computations specific to this function (laws, logic and engagement) are duplicated in each FAC. The system operates using the changeover technique : when both the yaw damper 1 and the yaw damper 2 are engaged, the channel 1 has priority. The channel 2 is synchronized on the position of the other channel and its associated servo-actuator is depressurized. This depressurization is performed by two solenoid valves. Each solenoid valve drives a by-pass valve. Only one solenoid valve is required to depressurize the servo-actuator. A pressure switch monitors the status of the solenoid valves. If the two servo-actuators are not pressurized, the rudder is centered to the neutral position (zero or the trimmed value). The rudder receives the yaw damper orders but these are not reproduced at the rudder pedals.
1EFF : ALL 1 22-63-00Page 1 1 1 Feb 01/98 1 1 1CES 1
Yaw Damper Function
Figure 001
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1 1 Feb 01/98
1 1
1CES 1
R FAC - Architecture of Yaw Damper Figure 002
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The Green hydraulic system supplies the servo-actuator No. 1 associated
with the FAC 1.
The Yellow hydraulic system supplies the servo-actuator No. 2 associated
with the FAC 2.
A current amplifier in the FAC delivers the orders to slave the
servo-actuator in position. A servovalve then executes these orders.
The slaving order is never interrupted even when a failure is detected :
the servo-actuator is neutralized through action on the electrovalves.
Each solenoid valve is under the control of an independent logic (C and
M).
The C1 and C2 transducers (LVDT) serve for the slaving. The S1 and S2
transducers (RVDT) permit to monitor this slaving.
Each FAC generates the priority order in the form of a hard-wired
discrete. The fluctuations of the 26 V/400 Hz power are compensated.
3.
Interface
_________ (Ref. Fig. 003) The figure given below shows the interconnections between the FAC and the yaw damper servo-actuator.
4.
Operation
_________
A. Principle
(1)
Manual mode In AP-disengaged configuration, the yaw damper function is linked to the ELAC.
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In normal mode, on the roll axis: The ELAC generates a lateral deflection law which integrates the control of the rudder (stabilization and turn coordination). The yaw damper carries out this law and indicates the correct achievement of this function through a hard-wired discrete. If necessary, the ELAC must operate in degraded law on the roll axis.
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