(5) 
 Fast Synchronization

(a)  
The system is locked into fast synchronization for 7 seconds when system power is applied, when system power is interrupted for more than 2 minutes, or when switching from one platform heading signal input to another as controlled by the power off and heading switching sensor. Fast synchronization is in effect until the magnetic error is reduced to less than 2 degrees, at which time the system automatically switches to the normal slaving rate of 1 to 2 degrees per minute. The system also will go into the fast synchronization mode when it is switched to SLAVED from DG, provided that the platform heading valid signal is present and the magnetic error is greater than 2 degrees. Fast sync is controlled by the fast sync control circuit. If the system is in the SLAVED mode and the magnetic error is greater than 2 degrees, the system will go into fast synchronization upon receipt of the heading valid signal. Fast synchronization does not occur when switching from DG to SLAVED if a valid signal is not present at the DG valid sensor.

(b)  
The heading error signal from the heading error amplifier is detected by the error detector and fed to the fast sync control. Output signals from the fast sync control are fed to the heading error amplifier (through the gain control), and to the superflag control, the frequency control and limiter, and the stepper motor control. This causes the following results when the system enters fast synchronization: 1) Less filtering is provided in the demodulator-filter-modulator. 2) The gain of the heading error amplifier is decreased. 3) The superflag output becomes invalid. 4) The output of the frequency control and limiter is increased. 5) The rate of the voltage-to-frequency converter is increased, causing the stepper

505 
Oct 20/84  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  34-21-02 Page 13 

505 
34-21-02 Page 14  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Oct 20/84 

motor to step at a faster rate.
6) The excitation voltage to the stepper motor is increased.

505 
Oct 20/84  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  34-21-02 Page 15 

(6) 
 Superflag Control

(a)  The superflag control normally provides an output for controlling operation of compass flags. The output also controls the clutched control transmitter (CX) steering output and the maintenance flag control. An invalid superflag output disengages the clutch of the clutched CX. The clutch is spring-loaded so that the steering output of the CX will go to a null during the time the superflag output is invalid. This prevents transmission of large error signals to the autopilot. When the superflag output is valid and 28 volts dc is applied to the clutch control, the clutched CX provides steering information to the autopilot. When the superflag output is invalid, the maintenance flag control is disabled. The superflag output will be invalid during any of the following conditions: 1) The servo CT null is off by more than 4 degrees 2) An open rotor winding in the servo CT 3) Loss of directional gyro heading signal 4) Loss of directional gyro heading valid signal 5) Loss of power to the system 6) System is in fast synchronization mode 7) Loss of magnetic field sensor excitation current

(7)  
Magnetic Field Sensor Excitation Monitoring

(a)  The magnetic field sensor excitation monitor is enabled in the SLAVED mode only. It monitors the current through the excitation winding of the magnetic field sensor. The output of the magnetic field sensor excitation monitor is applied to the superflag control so that when the system is operating in the SLAVED mode and excitation to the magnetic field sensor is lost, the superflag output will become invalid and flags will appear on the HSI and RDDMI of the affected system.

(8)  
Directional Gyro Data Monitoring

(a)  The output of the DG CDX is monitored by the heading data monitor. When the DG CDX is not excited, the superflag output is invalid.

(9)  
Servo CT Null and Continuity Monitor

(a)  When the servo CT is not at a null or if continuity does not exist in the rotor winding, the superflag output is invalid. Also, if continuity does not exist, or if the servo CT is not at a null, the maintenance flag comes into view and remains in view until manually reset with a magnet. The maintenance flag does not actuate when the system is in fast synchronization mode.

(10)
DG Valid Sensor

(a)  If a directional gyro heading valid signal is not present at the DG valid sensor, fast synchronization cannot be initiated and the superflag output will be invalid. The maintenance flag does not actuate under this condition.
　
中國航空網 m.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：737 AMM 飛機維護手冊 導航 NAVIGATION 1(69)