(2)
Two plug-in circuit card assemblies each contain a microprocessor that controls an arithmetic processing unit for making air data calculations. Both circuit card assemblies have large scale integration (LSI) integrated circuits that contain read only memory (ROM) for program storage, random access memory (RAM) for scratch pad memory, and peripheral integrated circuits (IC's) having I/O ports. All of the LSI integrated circuits are tied together by common buses. Calculations of the computer are performed on a time-shared basis.
(3)
Two pressure inputs and one temperature input are converted into 16-bit data words. Various reference, enabling, and command signals are received from the airplane and are used by the computing circuitry (using the pressure and temperature data) to provide outputs that drive airplane systems and indicators. The computer uses solid-state electronics to perform functions that were formerly carried out by mechanical devices. Synchros and potentiometers are "synthesized" using solid-state electronics. Also developed are hold signals, rate signals, and failure warning signals.
(4)
The computer contains a digital information transfer system (DITS) that generates a serial, bipolar output. An air traffic control (ATC) code is also generated. The computer also contains an extensive, self-test monitoring system.
(5)
A static source error correction (SSEC) program is stored in the instructional program. The SSEC program is used by the computer to compensate for differences in airplane type. The program to be used is selected by airplane program jumpers that inform the microcomputer which type of airplane the computer is in.
(6)
Outputs to the air data instruments from the air data computer(s) and air data computer interface to other systems are shown in Fig. 6.
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Feb 15/80 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-12-0 Page 9
AIR DATA COMPUTER-REMOVAL/INSTALLATION
1. Remove Air Data Computer
CAUTION: TO AVOID COMPUTER DAMAGE, PITOT AND STATIC SYSTEM PRESSURES MUST BE AT AMBIENT BEFORE PROCEEDING.
TO AVOID ELECTRIC FLIGHT RECORDER DAMAGE, FLIGHT RECORDER CIRCUIT BREAKERS MUST BE OPENED BEFORE PROCEEDING.
A. Open air data computer circuit breakers on panel P6 or P18.
B. Disconnect pitot and static pneumatic hoses from front panel.
C. Loosen cam-lock handles and remove computer.
2. Install Air Data Computer
A. Insert computer into case being careful to avoid stress and/or damage to electrical connectors on rear chassis panel.
B. Tighten cam-lock handles.
CAUTION: TO AVOID COMPUTER DAMAGE, PITOT AND STATIC SYSTEM PRESSURES MUST BE AT AMBIENT BEFORE PROCEEDING.
C. Connect pitot and static system pneumatic hoses to front panel.
D. Close air data computer circuit breakers on panel P6 or P18.
E. Make sure the hose connections are locked in the sealed position.
3. Test Air Data Computer
A. Provide electrical power.
B. The following steps list all self-tests. Perform those steps for self-test readout available.
NOTE: TEST VALID WHEN LIT light should come on and remain on while push-to-test switch is pressed. Switch must be held for approximately one-half minute for the FUNCTION switch position to allow instruments to stabilize. For other switch positions, light should come on in approximately two seconds.
(1)
Rotate self-test switch on front of computer to FUNCTION and press push-to-test switch. Verify that TEST VALID WHEN LIT light comes on.
(2)
Repeat step 3.B.(1) with self-test switch set to SLEW, HOLD, and FAIL WARN.
C. Remove electrical power if no longer required.
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Aug 01/95 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-12-11 Page 401
AIR DATA PRESSURE INDICATORS - REMOVAL/INSTALLATION
1. Remove Indicator
A. Open applicable indicator circuit breakers on panel P6 or P18.
NOTE: If servoed or servo-pneumatic indicator, also open applicable air data computer circuit breakers.
B. Loosen instrument mounting clamp and slide indicator out of instrument panel.
CAUTION: DRAW INDICATOR OUT OF INSTRUMENT PANEL WITH CARE TO AVOID STRESS AND/OR DAMAGE TO CABLE AND PNEUMATIC HOSES (IF ATTACHED) AT BACK OF CASE.
C. Disconnect electrical connector on rear of indicator case.
CAUTION: TO AVOID DAMAGE TO PNEUMATIC OR SERVO-PNEUMATIC INSTRUMENTS, PITOT AND STATIC SYSTEM PRESSURES MUST BE AT AMBIENT BEFORE PROCEEDING.
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