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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
6. AIRPLANES WITH EIS; Total Air Temperature Indication
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A. The total air temperature is displayed on the EIS secondary display on the pilots' center instrument panel. The display is a liquid crystal display. The digital data for the display is supplied from digital air data computer No. 1 on digital bus No. 2 (Ref Fig. 4 and 5).
7. Total Air Temperature Probe (Fig. 1 and 4)
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A. The outside air temperature probe contains non-inductive resistive transducer sensing elements and an anti-icing heater. Temperature variations of the slipstream airflow through the probe and sensor causes the element resistance to vary. The TAT (total air temperature) probe provides air temperature data to the digital air data computers and the flight data recorder. In flight, heating of the probe assembly is controlled by a switch on the pilots' overhead panel (Ref 30-31-00).
8. Digital Air Data Computer (Fig. 1, 4 and 5)
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A. The digital air data computer (DADC) is a solid-state device that uses pitot static pressure and air temperature inputs to compute air data information required by airplane displays and systems. In addition to the above inputs, 115-volt ac and 26-volt ac are provided to multipin connectors at the rear of the computer.
B. The computer consists of two pressure transducers, 11 plug-in printed circuit cards, a power supply and chassis assembly. The front panel (Fig. 1) provides two switches for self-test actuation, a self-test indicator light, a fault isolation test connector for off-aircraft trouble shooting and pitot static pressure input connectors. Two electrical connectors mounted on the back of the chassis provide interconnection with the airplane wiring.
C. The TEST SELECT switch manually selects built-in test to be performed as follows: FUNCTION - transmits fixed values on all the computer signal output lines. SLEW - sets altitude rate to 600 feet per minute. FAIL - activates all failure warning outputs.
The PUSH TO TEST pushbutton switch initiates the built-in test and the TEST VALID WHEN LIT indicator light comes on within 2 seconds after manually activated test is successfully completed and remains on if there is no failure.
9. Operation
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A. General
(1)
The air data computer system is depicted in the block diagrams (Fig. 2 and 3), system schematic (Fig. 4) and system interface diagrams (Fig. 5, 6 and 7).
(2)
Power input to DADC No. 1 is shown on Fig. 4 and is supplied from P18 circuit breaker panel. Power input to DADC No. 2 is shown on Fig. 7 and is supplied from P6 circuit breaker panel.
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