22-11-00
 ú ú 03 Page 13 ú Nov 12/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
 4.  Automatic Flight Controls (AFC) Accessory Unit
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 A.  The AFC accessory unit is mounted on the E1-3 shelf in the electrical and electronic equipment bay. The unit is a 3/8 ATR long unit which is retained in the rack by a camlock handle which engages in a rack-mounted adjustable swivel bolt. Electrical connections are provided by a DPX connector on the rear of the unit which mates with a rack-mounted connector.
 B.  The unit contains several relays, time delay gates, a circuit interrupter and other components used for interconnecting the DFCS.
 5.  Flight Mode Annunciator (FMA)
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 A.  One flight mode annunciator (FMA) is installed on the P1 panel and the other on the P3 panel. Each FMA is composed of three sections: one section provides AP/FD system (AFDS) mode annunciation with engage status and warning; one section provides A/T annunciation and warning; and the third section provides N1 LIMIT annunciation and FMC warning.
 B.  The AFDS mode annunciators on the left side are: L NAV-HDG SEL, VOR LOC, G/S, FLARE, VNAV PATH-VNAV SPD, ALT ACQ-ALT HOLD, V/S, MCP SPD-TO/GA and A/P STATUS annunciators: CWS ROLL-SINGLE CH, CWS PITCH-A/P OFF. The AT mode annunciators on the center are: FMC SPD-N1, MCP SPD-RETARD, ARM-A/T LIMIT, THR HLD-GA. The N1 annunciators on the right side are: CRZ, CLB, REDUCED-CON, TO-GA. Warning lights, A/P, A/T, and FMC, with push-to-reset feature, are installed in the lower right area of the FMA. A 3-position test switch is located adjacent to the FMC 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.
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 22-11-00
 ú ú 04 Page 14 ú Feb 25/87
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 D.  The warning lights are composed of colored lens caps, red for A/P and A/T and amber for FMC. 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.
 E.  The FMA contains self-test circuits to test the operation of the annunciator electromechanisms. A 3-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.  Attitude Director Indicator (ADI)_________________________________
 A.  The attitude director indicator (ADI) provides attitude information and flight director commands. An ADI is located on each of the pilots panels (P1 and P3). The flight director commands are described in this section. The attitude display is described in 34-28-00.
　
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