34-28-01
ú ú 05 Page 22 ú Nov 12/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
26V AC
26V AC
HDG
MAG
HDG
VALID
GND
COMMON
26V AC
+5V LIGHTING
COMMON
26V AC
26V AC
STATUS OUT
VALID IN
CLOCK
WORD
SYNC
DATA
CLOCK
WORD
SYNC
DATA
STATUS OUT
VALID IN
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH EFIS ú
34-28-01
ú ú 04 Page 23 ú Feb 25/87
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
A. The RDDMI's display magnetic heading supplied by the IRS. The HEADING failure flag appears on the instrument face if the IRS is off or the data displayed is invalid.
CAUTION: FAILURE TO OBSERVE ELECTROSTATIC DISCHARGE PRECAUTIONARY PROCEDURES
_______ WHEN HANDLING THE RDDMI MAY RESULT IN DEGRADATION OR FAILURE OF THE RDDMI.
B. The RDDMI's are located on the captain's (P1) and F/Os (P3) instrument panels. Each RDDMI has three rear-mounted connectors.
C. The RDDMI is powered from a 26 volt ac power source. The power supply produces the AC and DC voltage to operate the heading servocircuit.
D. The RDDMI includes a servocircuit that drives a magnetic heading card, and a flag circuit and flag that monitors the status of the magnetic heading source and the operation of the servocircuit. Three-wire heading information is applied to a synchro-resolver which supplies an output to a demodulator and amplifier which in turn drives the motor and card and repositions the synchroresolver rotor. An AND gate monitors excitation from the synchroresolver, proper follow up on commands by the servocircuit, dc from the power supply, and the valid from the heading source.
12. Vertical Speed Indicator (Fig. 12)
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A. Two vertical speed indicators (VSI) are located on the main instrument panels. The captain's VSI is on the P1 panel and the first officer's VSI is on the P3 panel.
B. The vertical speed indicators are powered by 115v ac, 400 Hz, single phase voltage. The captain's VSI is powered by the electrical power bus No. 1 from panel P18. The first officer's VSI is powered by the electrical power bus No. 2 from panel P6.
C. The VSI displays the inertial vertical speed in thousands of feet per minute. The vertical speed is displayed by a pointer on a fixed, nonlinearly indexed scale. This scale is expanded between 0 and |1000 feet per minute for better resolution of vertical speed in low operating ranges.
D. The captain's and first officer's VSI's receive vertical speed data from both IRU 1 and IRU 2 on ARINC 429 data busses. The selection for input data is made through the IRS transfer relay.
E. An OFF flag will appear in the event of invalid or non-computed data from the IRS.
13. IRS Transfer Switch (Fig. 13)
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A. The IRS transfer switch is situated on the P5 panel and controls IRS transfer relays 1 and 2, located on the E1-2 equipment shelf. These two relays transfer analog magnetic heading signals and valids from either DAA to the RDDMI's, and supply a ground to the EFIS SG's, the VSI's, and the weather radar R/T unit. The ground enables selection of the alternate IRU as the source for digital information to these components.
B. Interlock contacts on the IRS transfer relays prevent them both being switched out of their "NORMAL" position at the same time.
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