22-11-01
ú ú 08 Page 23 ú Mar 15/95
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
15. Flap Position Transmitters (Ref 27-51-00)__________________________
A. The flap position transmitters provide DFCS inputs indicating actual flap position. The two flap position transmitters are located on the outboard flap torque tubes. The units are mechanically driven by the flap torque tubes. Electrical angular rotation of the synchro from 0 degrees to 270 degrees represents flap positions from 0 degrees to 40 degrees. This information is used in the pitch channel to generate program commands for use in the takeoff and go-around modes.
16. Pressure and Limit Switches___________________________
A. Detent Pressure Switch
(1)
The purpose of the Detent Pressure switch is to sense when hydraulic pressure has been applied to the A/P actuator detent piston. The switches are attached to the A/P elevator actuators at the pressure port sensing output. The pressure switch is a cylindrical unit with one electrical connector to provide a continuity signal when pressure is sensed.
(2)
The FCC provides the signal for the activation of solenoid valve No. 2 on the actuator. This solenoid allows hydraulic fluid to flow to the detent piston. The pressure switch senses this hydraulic pressure and will close. The closing of the switch provides continuity for a signal from the FCC which then will be returned to the FCC to indicate that the detent piston is pressurized. Failure of this switch closing will cause the A/P to disengage.
B. Flap Up Limit Switch (AMM 27-51-00)
(1) The flaps up limit switches provide the FCC and the stabilizer trim servomotor with flaps up or down logic voltage. There are two flaps up limit switches: S245 Flap Switch No. 1, also known as Flaps Up Switch (AMM 27-51-87/401) and S290 Flap Switch No. 2, also known as Mach Trim Flap Switch (AMM 22-21-31/401). The flaps up limit switches are located on the flap control unit in the aft right corner of the main wheel well. The flaps up limit switches are mechanical-cam operated with 28v dc supplied to the common contact. The normally closed (flaps up) contact provides voltage to the FCC and the normally open (flaps down) contact provides outputs to the FCC and stabilizer trim servomotor.
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