3. Flight Instrument Amplifier Rack
A. The roll and pitch servo-amplifiers and the warning flag amplifiers are all plug-in type units which plug into the appropriate amplifier rack.
4. Attitude Director Indicator (ADI)
A. Each artificial horizon (contained in the ADI) consists of a moving tape assembly which displays the horizon line, pitch scale and roll index. The tape assembly is coupled to the rotors of the roll and pitch synchros and to the roll and pitch servomotors. When the servomotors turn, the synchros and the tape assembly are positioned simultaneously. Airplane attitude in roll is read from the roll index against the roll scale, and airplane attitude in pitch is read from the pitch scale against the miniature airplane symbol. Adjustment of the tape in pitch is provided for, through the pitch trim adjuster at the lower left corner of the indicator.
B. A gyro warning flag is provided in each ADI to indicate loss of power, or malfunction of the gyro or of either servo-amplifier circuit in the system.
5. Operation
A. Both systems are made operational by closing the system circuit breakers. After a brief period of time the gyros will erect and each ADI should indicate a level condition in both pitch and roll axes.
B. Each system operates as follows: when the airplane is displaced in the roll plane, the gyro will transmit an ac signal which is not only related in amplitude to the degree of displacement, but also phase oriented to differentiate between left and right roll. The signal is passed to the roll servo-amplifier where it is amplified to drive the servomotor, which in turn drives the horizon tape. This ac signal is fed via the roll synchro on the roll motor shaft to ensure that the motor stops as soon as it has turned sufficiently to null out the error signal. Pitch displacement signals are handled in a similar way, and the electromechanical design is such that the horizon tape is able to respond to both pitch and roll signals simultaneously (Fig. 2).
C. The operation of the transfer switch and relays is illustrated in Fig. 3 and 4. Figure 3 shows how the relay coils are connected with the ground through the relay contacts. The switch is shown in its NORMAL setting. Assume that the transfer switch is now set to BOTH ON 2. This switch puts a ground on the lower end of latching relay coil A via contacts B2 and A1; and since the other end of that coil is connected to 28 volts dc, it will now latch over to the alternate set of contacts and remain there until energized once more. Note that the ground is removed from the coil by the transfer of contacts at A1. In order to ground the coil once more and switch the relay back again, it will be necessary to return the switch to NORMAL. The switching to BOTH ON -1 is carried out in a similar way.
541
Aug 01/74 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-22-0 Page 3
K77848
Transfer Switching Circuits 541
34-22-0 Figure 3 Feb 01/74
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
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5C8 Attitude Reference System SchematicFeb 20/89 Figure 3 34-22-0 Page 5/6 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
D. The switching contacts shown in Fig. 4 are a continuation of those shown in Fig. 3 and transfer signals in the system. With the transfer switch in NORMAL position, the captain's ADI is slaved to the No. 1 vertical gyro and the gyro warning flag is monitoring the slaving circuits and vertical gyro No. 1. With the transfer switch in BOTH ON -2 position, the captain's ADI is slaved to the first officer's ADI and the gyro warning flag is monitoring the slaving circuits, vertical gyro No. 2, and the first officer's warning circuits. The first officer's components operate the same as the captain's, but with vertical gyro No. 2 as the primary reference. It can be seen that proper selection of the transfer switch will provide attitude reference to both ADI's and both flight directors from either vertical gyro. The inverter interlock logic will disconnect the first officer's warning circuits when the inverter comes on with the transfer switch in BOTH ON -1 position. Disconnecting these circuits will prevent them from adding to the current drain of the battery under emergency power conditions.
E. The transolvers in the ADI's have three windings: a three-coil stator; and two, one-coil rotors, wound 90 degrees apart on the same core. Normal operation of the servo loop will ensure that the rotor that feeds the servo-amplifier is always at or near a NULL. This signal is fed to a null sensing circuit in the flag amplifier where it is used as a reference from the servo loop circuit. In the absence of this signal, the flag amplifier will fail and the warning flag will appear. The flag amplifier receives this NULL from both pitch and roll servo circuits so that a malfunction in either servo loop will trigger the flag.
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