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INTERNALS SAME AS FOR LEFT CHANNEL COMPONENTSAIRPLANES WITH CONTROL WHEEL STEERING
Autopilot/Flight Director System Power Distribution SchematicFigure 4
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the FCC power supply receives 115v ac and generates dc voltages required for internal FCC circuitry. The 115v ac is also reduced to 26v ac to provide servo LVDT and transducer excitation.
(d) Autopilot/Flight Director System DC Power 1) FCC DC Power a) Standby 28v dc power is supplied to the FCC as an independent power source for A/P caution and warning monitor circuits. b) GUN 051; left FCC 28v dc servo power is provided to the left FCC. It is used to power the aileron, elevator, and rudder arm and engage solenoids. The solenoids are energized when the FCC ARM/ENGAGE logic is satisfied. Within the MCP, the servo power is used by the CMD engage switches. c) GUN 001-050, 052-999; left FCC 28v dc servo power is provided to both the FCC and the MCP. Within the FCC, this is used to power the aileron, elevator, and rudder arm and engage solenoids. The solenoids are energized when the FCC ARM/ENGAGE logic is satisfied and the MCP DISENGAGE bar is up. 2) MCP DC Power
a) The primary source of 28v dc for the MCP power supply is provided by Left and Right Mode Cont PNL circuit breakers.
(e) Autopilot/Flight Director System Autoland Bus Isolation (Fig. 5) 1) Three independent AC and DC power sources are required to initiate a fail-operational Category III landing. The main engine-driven generators are the normal sources for two of the independent channels and the standby power system (battery and static inverter) provides the third. If one engine-driven generator is inoperative, the APU-driven generator may be substituted for that source.
2) The L and C AFDS channels are supplied from the left power system and the R AFDS channel from the right power system. The bus tie breakers (BTBs) are normally open but will close automatically to maintain power to a main AC bus if the associated generator fails.
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3) If the APU is running prior to a generator failure, the auxiliary power breaker (APB) and the associated BTB will close allowing the APU generator to power the failed generator's channel. If the APU is not running, both BTBs will close and the opposite engine-driven generator will assume the load (Ref 24-22-00).
4) The ground allows the ISLN REQUEST RELAY (K122) to energize thereby providing 28 vdc to the AUTOLAND RELAYS (K526 and K527). The 28 vdc energizes both relays which in turn provides 28 vdc to energize the CENTER BUS ISOL RELAY (K123). With K123 energized, the MAIN BAT RELAY (K104) provides power to energize the CENTER BUS XFER RELAY (K107). This removes the ground to the FCC's A/L BUS ISOL IN pin. The open signals the FCC's that the center buses are now powered from the hot battery bus (DC) and static inverter (AC). If either the left or right INSTR BUS VOLTAGE SENSE UNIT (M1079 or M1217) de-energizes, then the ground to the FCC's A/L BUS ISOL in pin is completed.
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