(b)
Detector 2. This unit detects movement of the stabilizer after the command is initiated. A stabilizer movement of greater 0.5° in 10 seconds is required to prevent a warning.
(c)
Detector 3. This unit detects an elevator A/P actuator position of greater than 5° from the neutral shift position.
22. DFCS Operation (Fig. 13)______________
A. Engage Interlock Operation (Fig. 13)
(1)
The autopilot is engaged by pressing one of the four pushbutton engage switches (CMD or CWS). The switches cannot be selected if certain conditions are not satisfied. When all conditions are met the switch logic is allowed to change from the reset condition thus enabling the pushbutton switches to be engaged. The engage switches remain in CWS or CMD if hold interlocks are maintained and a disengage discrete is not present.
(2)
The A/P engage switch provides a discrete to energize the arm solenoid in the A/P actuators. After the A/P actuator is synchronized with the surface, the detent solenoid is energized. The A/P aileron force limiter clutch is also energized in CWS or CMD. The A/P warning light circuit is armed when the A/P is engaged in either CWS or CMD.
(3)
A/P Engage Switch Unlock
(a) The interlock which allows the A/P pushbutton to be engaged requires that the unlock logic from the A/P engage interlock table (Fig. 15) be high. When this logic is satisfied the reset condition is removed from the switch logic, allowing the engage relay to be energized and either CWS or CMD selected.
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22-11-01
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH EFIS ú
22-11-01
ú ú 07 Page 43 ú Nov 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
(4)
A/P Engage Switch Hold
(a) The A/P engage switch relay remains energized if the hold logic is high and the disengage logic is low. The hold logic is shown on the A/P engage interlock table. The A/P general disengage logic is shown on the A/P engage interlock table (Fig. 15). The disengage events associated with roll modes are shown on the A/P roll mode disengage table (Fig. 16). The disengage events associated with the pitch modes are shown on the A/P pitch mode disengage table (Fig. 17).
(5)
A/P Actuator Arm Solenoid
(a) Power to energize the arm solenoid is through contacts of the A/P engage switch circuitry. The arm solenoid is energized in either CWS or CMD.
(6)
A/P Actuator Detent Solenoid
(a) The logic which energizes the A/P actuator detent solenoid depends on the flight condition. These conditions are discussed in the following paragraphs: 1) A/P Engage Switch First Selected
a) When the A/P engage switch is engaged to CWS or CMD, the arm solenoid is energized. This starts the synchronization of the A/P actuator to the surface. When this synchronization is complete, the detent solenoid is energized. Energizing of the detent solenoid activates the A/P actuator.
2) A/P Engage Switch Cruise Operation
a) During cruise mode of A/P operation, only one A/P is engaged at any time even if both A/P switches are engaged. When the second A/P is engaged, the second A/P actuator is synchronized and then energizes the detent solenoid. Disengagement of the first selected channel is through the use of detent pressure switch. This assures that the second channel is fully pressurized before the first selected channel is disengaged.
3) Dual Approach A/P Operation
a) When both A/Ps are engaged to CMD prior to APP OC in dual operation, the arm solenoids in both the elevator and aileron A/P actuators of the second A/P to CMD are energized. A/P actuator synchronization is continuous until APP OC plus approximately 10 seconds, when the detent solenoid of the second in command is energized.
b) When both A/Ps are engaged during approach and a GA is initiated, all arm and detent solenoids remain energized. If the roll A/P GA is exited, the A/P aileron detent solenoid of the second selected is de-energized. When the pitch A/P GA is exited, the A/P engage switch of the second to CMD is returned to OFF.
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