GJ (WA)
B. Trim servomotor power is controlled by the autopilot stabilizer trim circuit in the AFCS computer. Power to the clutch solenoid is supplied through the autopilot trim cutout switch on the control stand. When the autopilot trim cutout switch is placed in the CUTOUT position, power is removed from the motor and clutch solenoid. The stabilizer trim limit switches also remove power from the clutch solenoid. Protection against a hot short (simultaneous trim-up and trim-down command) is provided in the AFCS computer.
13. AFCS Switches, Lights, Aural Alert Unit and Status Annunciator
A. The AP disconnect switches are located on the outboard horns of the pilot's control wheels. The switches disengage the AP and reset the disengage lights and aural warning. The switch NC (normally closed) contacts are in the AP engage circuit and the NO (normally open) contacts are in the reset circuit.
B. The AP CRUISE TRIM switch on the P8 panel is a two-position switch, NORMAL and CUTOUT, which provides stabilizer trim clutch control. The switch must be in NORMAL position to permit AP engagement and automatic stab trim operation.
C. The STAB OUT OF TRIM warning light on the P2 panel illuminates amber when an AP system is engaged and a sustained stabilizer out of trim condition exists. The light will extinguish when the AP is disengaged or the out of trim condition is nulled.
D. The ALTITUDE ALERT lights, located on the P1 and P3 panels, illuminate steady when approaching a selected altitude (between 900 and 300 feet) and a flashing light and warning horn in aural alert unit (P5) come on when an altitude error exists (beyond 300 feet).
E. An autopilot status annunciator is installed on the pilots main instrument panel P3 (Fig. 1). The unit provides a display to indicate autopilot operational status by FAA flight category that the airplane is authorized within and whether an autopilot approach flight check is required. The top annunciator window readouts are; CAT II A/P ILS; CAT II SINGLE LAND; CAT II/IIIA DUAL LAND; which are green and CATEGORY I which is amber. The bottom annunciator window readout is FLT CHECK REQ'D which is amber and 5 blank positions. Readouts are positioned by operating ratchet wheels which are engaged and rotated by a small screwdriver, etc., thru access holes located on the right side of the unit.
14. Signal Interface
A. Attitude Reference System Interface (Fig. 5)
(1)
The attitude reference system is connected thru switching relays to a respective AFCS computer. System 1 (VG 1) or AUX VG is connected to AFCS computer A (A system inputs) and system 2 (VG 2) or AUX VG is connected to AFCS computer B (B system inputs). Attitude reference cross channel connections are provided for flight directors. The attitude systems provide pitch and roll three-wire information into the AP/FD systems. The attitude valid signals are in the engage interlock circuit for the respective system.
(2)
Loss of attitude (gyro) valid will disengage the autopilot. The autopilot cannot be re-engaged until an attitude valid signal is present.
(3)
Operation of the attitude transfer switch provides an additional VG valid interrupt. When electrical power is switched to the transfer bus an interlock opens to disengage the autopilot. Electrical power must be normal to engage the respective AFCS computer.
5GJ
Jun 20/85 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 22-11-01 Page 13
AFCS Attitude Interface Diagram 595
22-11-01 Figure 5 May 01/01
Page 14
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
505 AFCS Compass Interface Diagram (WA N235WA)
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