737 AMM 飞机维护手册 AUTO FLIGHT 自动飞行 1(57)

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5.  AFCS Annunciator
A.  One AFCS flight mode annunciator panel (FMA) is installed on the P1 panel and one on the P3 panel. Each panel is composed of three sections: one section provides AP/FD mode annunciation AP with engage status and warning; A/T annunciation and warning; and third, the PDC annunciation.
B.  The AP/FD mode annunciators on the left side are: L NAV-HDG SEL, VOR LOC, GS, FLARE, V NAV – SPEED, ALT ACQ-ALT HOLD, V/S, PDC SPD – TO/GA and A/P STATUS annunciators: CWS ROLL – SINGLE CH, CWS PITCH – A/P – OFF. The A/T mode PDC annunciators on the right side are: CON – TURB, HOLD – CRZ, DES – CLB, GA – TO. Two warning lights A/P and A/T with push-to-reset feature are installed in the lower right area of the FMA. A two-position test switch is located adjacent to the AT warning light.
C.  Each of the mode annunciators is a prismatic electromechanical device which displays the annunciator legends. The device consists of a three-faced prism and two prism-driving solenoids. Each face of the prism is colored and engraved with an annunciator legend; however, only two faces are engraved. The third face is blank (black) and is in the blank display position when deactivated. The prism is electromechanically rotated in either direction about the longitudinal axis so that one of the other faces (upper and lower) can appear in the display position. A solenoid actuated by a remote mode signal (dc ground) drives the prism mechanism. The prism is driven 120 degrees in the required direction to display the corresponding mode legend. When the solenoid loses the signal, the prism reverts to the original position (display of the blank face). The second solenoid is used with another mode and drives the prism in the opposite direction. The prisms are illuminated constantly by background lights. The mode annunciators display black letters on white during mode arm conditions and black letters on green during mode engage conditions. A/P status annunciators display black letters on amber for CWS ROLL, and CWS PITCH, and SINGLE CH; black letters on white for A/P OFF.
D.  The warning lights are composed of two filtered sections, a red filter and an amber filter. Each section has two lamps with AP1 warning power to one lamp and AP2 system power to the other. The lights are illuminated by application of a ground. Pressing the warning light assembly operates a switch which completes 28 volts dc to the corresponding autopilot channel to extinguish the light and/or stop a warning horn.
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Oct 20/89  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  22-11-01 Page 9 

E.  The FMA contains self-test circuits to test the operation of the annunciator electromechanisms. A two-position toggle switch is provided to perform the test. Test 1 is used to check the upper prism face electromechanisms. When the switch is held to 1, a dc ground is applied to all solenoids corresponding to the upper prism faces. All the upper face legends appear simultaneously in the display position if the related circuits and mechanisms are functioning properly. Similarly, the test 2 switch is used to test the lower prism face electromechanisms. The test switches also illuminate the warning lights. A power supply and logic circuits are within the FMA for operating the mode annunciators. The pilot’s panel lighting circuits provide power for the FMA background lights (Ref Chapter 33).
6.  Control Wheel Steering (CWS) Force Transducers
A.  Three identical force transducers are installed in the captains and first officers control columns, two in the pitch axis and one in the roll axis. The pitch axis force transducers are located in the forward control quadrants below each control column. The roll axis force transducer is mounted between the control shaft and aileron drum below the captains control column.
B.  Each force transducer provides dual electrically isolated ac output signals that are proportional to the force applied to the control wheel or column. The signals are used by the autopilot computers when the system is engaged in CWS (manual) mode. When the autopilot is engaged in CMD mode the CWS signals are monitored. CWS signals, above a preset level (high detent), disconnect CMD mode and engage CWS mode.
7.  Three-Axis Accelerometer
A.  Two three-axis accelerometers are installed on the left forward sidewall of the forward cargo compartment (behind the hardliner) below the J10 box. One unit is used by AP/FD channel A and the other is used by AP/FD channel B. The lateral accelerometer signal is used for roll axis computation and the normal and longitudinal accelerometers are used for pitch axis computation. The unit provides a damping term for the respective axis for system computation.
8.  Aileron Force Limiter
A.  The force limiter is splined to the aileron drum at the bottom of the captain’s control column. The force limiter consists of an electromechanical clutch, switch, a spring-loaded arm and cam assembly, plus motor-driven limit switches. The electromechanical clutch and switch are activated when the roll axis is engaged. The force limiter mechanically limits the control wheel angle by progressively increasing the force within the system to cam out autopilot control at the AP actuator. Motor-driven switches within the force limiter, which are controlled by trailing edge flap position, determine the control wheel angle limit. With trailing edge flaps up, the limit is 17 degrees. With trailing edge flaps down (1 unit position and beyond) the limit is 25 degrees. This limits the rate of roll which the autopilot hardover maneuver capability. The clutch switch ensures the force limiter is engaged. If the clutch disengages, the switch opens the AP engage switch holding coil circuit.
　
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