737 AMM 飞机维护手册 导航 NAVIGATION 1(96)

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K.  HDG-GA Mode
(l)  The HDG-GA mode enables the pilot to fly the airplane to and maintain a selected heading while maintaining the airplane at the fixed GA pitch-up command. When HDG mode is selected from the GA mode without stopping in OFF mode, the 14-degrees pitch up command is retained in the pitch channel. The fixed pitch-up command can be overridden by selecting ALT HOLD or another mode on the mode selector. In the roll channel, the system will provide commands to fly to the selected heading. In this mode, the ROLL GA signal is not generated thereby allowing the heading error signals to be added to the roll attitude signals and the roll steering commands generated as in the HDG mode.
L.  Altitude Hold Submode
(l)  The altitude hold submode can be used in HDG, VOR/LOC and AUTO APP modes. If the air data computer fails, a warning flag voltage switches off the CADC relay in the accessory box. This opens the altitude hold circuit and the ALTITUDE HOLD switch returns to the OFF position. In AUTO APP mode, as soon as glide slope capture is generated a transistor is turned off in the computer, opening the altitude hold solenoid circuit and the ALTITUDE HOLD switch springs to the OFF position. This enables glide slope deviation signals to be used in the pitch channel instead of pressure altitude deviation signals.
576 
Feb 15/79  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  34-26-0 Page 19 

 

M.  Computer Flag Circuit Operation
(1)  
Figure 5 shows a chart diagram of the computer flag circuit which provides a ground to operate the computer flag in the ADI. If the various inputs to the computer are correct and the computer is functioning properly, the computer switch will be on to complete the computer flag solenoid circuit and pull the COMPUTER flag out of view.

(2)  
The AND circuit in the ADI monitors the input DC voltage and the flag circuit signal from the computer. The switch monitors the servo error signal from the null detectors. If the null detector in either the roll or pitch channel detects more then 3 degrees of error between the command signal and the V-pointer position signal, the switch circuit will be off. Therefore, the switch to ground for the flag solenoid will be open allowing the CMPTR flag to come into view. In addition, if either the DC voltage fails or the flag circuit signal is not present, the AND circuit will be off and the flag solenoid will not operate allowing the CMPTR flag to come into view.

(3)  
The roll monitor and pitch monitor circuits in the computer comprise transistor/diode logic to monitor the various inputs. In the illustration, the input signals are read horizontally and the relevant inputs for a specific mode are read vertically. The "x" indicates that the signal voltage is present. For example, in the roll monitor block in VOR/LOC mode the input signals which are essential to complete the AND gate are PITCH MONITOR, NAV FLAG, ATTITUDE VALID, COMPASS MONITOR, HEADING POWER (28V-dc) and ATTITUDE POWER (38V-dc).

(4)  
The pitch monitor signal is produced in the pitch monitor circuit from various inputs, depending on the operating mode of the pitch channel which has been selected. If AUTO APP is selected, the computer will monitor the HDG inputs in the pitch monitor until the computer is switched by a glide slope capture voltage. In GS mode, although GS is selected, the computer will be in either MANUAL PITCH or ALT HOLD before G/S capture.

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34-26-0 Page 20  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Feb 15/79 

T53848
576  Flight Director Warning Flag Schematic 
Feb 15/79  Figure 5  34-26-0 
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

 

FLIGHT DIRECTOR SYSTEM - TROUBLE SHOOTING
EFFECTIVITY

Airplanes with Collins FD-110 Flight Director System
1. General
A.  Flight director system trouble shooting is provided by fault isolation procedure charts based upon performance of the adjustment/test procedures. The chart lists trouble symptoms and probably causes. An isolation procedure is then given to follow and the remedy to solve the fault for each isolation procedure.
B.  Before trouble shooting the system, ensure that operating power is available, and that all circuit breakers required per Adjustment/Test are closed. Assure that all systems supplying information to the Flight Director System are operating properly. Set all transfer switches to normal.
2.  Fault Isolation Procedure Charts
A.  To use the chart, find the trouble symptom in the chart which best describes the fault indications encountered. Perform the isolation procedure listed for that system. Depending upon whether the procedure is OK or NOT OK, perform the corrective action for that step and then repeat the step at which the failure was encountered.
　
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