circuit breaker 14CC1. The components associated with the FAC2 are supplied with 26V/400 Hz:
-
From the 115VAC BUS 2 2XP through the 26VAC BUS 2 231XP-A via 3A circuit breaker 14CC2.
C. Internal Power Supply
(Ref. Fig. 003)
(1) Behaviour of the FAC under 28V transients Cutoffs of the 28V power supply may occur for periods lasting up to 200 ms especially in case of engine failure. The system is designed as follows (power supply and safeguard):
(a) Cutoffs less than or equal to 10 ms. The operation remains normal, without safeguard, as the power supply absorbs this cutoff. In this case, the solenoid valves are not energized which has no impact (de-energizing time of the solenoid valves = 35 ms).
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28VDC Power Supply - Block Diagram
Figure 001
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26VAC Power Supply - Block Diagram
Figure 002
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FAC - Internal Power Supply
Figure 003
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(b)
Cutoffs less than 200 ms. The normal operation is interrupted (return to synchro mode) and the context is safeguarded (computation, ARINC transmission and reception). In this configuration, the changeover order is transmitted and the external validations are interrupted (solenoid valves, validation of servo-actuator, etc.). At power restoration, the considered system is re-activated (hence possibility of changeover) with the safeguard context after temporary inhibition of the power comparators.
(c)
Cutoffs greater than 200 ms.
1_ In-flight cutoffs
These are long cutoffs. Normal operation is interrupted. The
context (ARINC and computation) is lost (transmissions
interrupted).
The FAULT legend is on and the changeover order is given.
At normal power restoration:
- The content of the computer is reset
- The system returns to synchro mode. The FAULT legend remains
on.
Pilot action on the pushbutton switch is required to re-engage
the system.
2 Cutoffs on the ground
_ During long cutoffs on the ground, the operation is different to avoid any re-engagement action by the pilot. At normal power restoration:
-
The failure is cleared (FAULT legend off)
-
The system takes over from a null order. If the cutoff exceeds 5 s, the safety tests are re-initiated. This operation is acceptable in the event of engine failure if no untimely significant movement of control surfaces is induced. As the FAC cannot keep the solenoid valves of the yaw damper servo-actuator energized, a centering of the rudder to the initial position can happen for any 28V cutoff greater than 35 ms (if only one FAC is available). The table given below reports the FAC behaviour under 28V cutoffs:
1EFF : ALL 1 22-67-00Page 5 1 1 Feb 01/98 1 1 1CES 1 -------------------------------------------------------------------------------| 28V CUTOFFS | FAC SAFEGUARD | FAC MODE | COMMENTS | |--------------|-----------------------|--------------|-----------------------| | Less than |- Context undisturbed |- No change-|- FAULT legend off | | 10 ms |- Servo-actuator vali- | over |- Re-engagement not | | | dation interrupted | | required | | | | |- Operation in normal | | | | | function | |--------------|-----------------------|--------------|-----------------------| | Less than |- Context safeguarded |- Changeover |- FAULT legend on | | 200 ms |- Servo-actuator vali- |- Synchro mode| during cutoff | | | dation interrupted | during cut- |- Re-engagement not | | |- Temporary inhibition | off | required | | | of power comparators |- Return of |- Normal function with | | | at restoration | priority at | possible switching | | | | power res-| from FAC1 to FAC2 | | | | toration | and return to FAC1. | |--------------|-----------------------|--------------|-----------------------| | IN FLIGHT |- Context lost with |- Changeover |- FAULT legend remains | | Greater than | re-activation and |- Synchro mode| on after power res-| | 200 ms | reset | at power | toration | | |- Servo-actuator vali- | restoration |- Re-engagement possi- | | | dation interrupted |- No return | ble after power res- | | | | of priority | toration | | | | |- The other FAC ful-| | | | | fills the function | | | | | and the pilot can | | | | | select this FAC | |--------------|-----------------------|--------------|-----------------------| | ON THE GROUND|- Context lost with |- Changeover |- FAULT legend goes | | Greater than | re-activation and |- Synchro mode| off after power res- | | 200 ms | reset | at power | toration | | |- Servo-actuator vali- | restoration |- Re-engagement not | | | dation interrupted | and re-en-| required | | | | gagement of |- Return to this FAC | | | | synchro per-| after synchroniza-| | | | formed | tion | -------------------------------------------------------------------------------
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