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MAINTENANCE MANUAL
(g)
GUN 001-050, 052-999; NO AUTOLAND 1) The NO AUTOLAND display is enabled during the entire
flight. To receive a NO AUTOLAND display, at least two FCCs must determine that a NO AUTOLAND status exists. When the P/RST switched is pressed, the reset flip-flop sets. This clears the display if the fail status is corrected.
(h)
GUN 051; MANUAL LND 1) The MANUAL LND display is enabled only during the approach
mode. To receive a MANUAL LND display, at least two FCCs must determine that a MANUAL LND status exists. When the STATUS switched is pressed, the reset flip-flop sets. This clears the display if the fail status is corrected.
(4) Autoland Status Annunciator Drive
(a)
FCC Outputs
1) Software digital output signals in the FCC are converted to analog and supplied to hardware drivers. The drivers are inhibited during a power loss or computer failure, to prevent a false annunciation. The outputs of the three FCCs are connected in parallel to the ASAs.
(b)
Display Drive
1) The top and bottom displays are driven when a ground is provided by the FCC. The ground completes the 28 vdc circuit to energize the magnetic coils and operate the mechanical display. Standby 28 vdc power connects in parallel with normal 28 vdc power. This provides a back-up source of power. A ground to the B side of the display overrides a ground to the A side.
(c)
Switches
1) GUN 001-050, 052-999; Diodes isolate the primary control from the test switches and allow testing the displays. Operation of the test switches checks power and display operation. Pressing TEST 1 displays both A faces. Pressing TEST 2 displays both B faces. The P/RST switches are paralleled and allow resetting the software logic.
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2) GUN 051; Diodes isolate the primary control from the test switches and allow testing the displays. Operation of the test switches checks power and display operation. Pressing TEST 1 displays the top A face. The bottom A face is not tested since it is not used. Pressing TEST 2 displays both B faces. The STATUS switches are paralleled and allow resetting the software logic.
(5) Autopilot/Flight Director System Caution and Warning Annunciation (Fig. 9)
(a) Autopilot Caution
1) Any autopilot failure requiring crew attention illuminates the AUTOPILOT caution light. A master CAUTION light is also illuminated, the EICAS computer displays an AUTOPILOT message, and an owl aural warning sounds (Ref 31-51-00). A power or computer failure inhibits the caution output to prevent a false annunciation. The following conditions cause a caution output signal prior to multi-channel engage only: a) AIRPLANES WITH CONTROL WHEEL STEERING;
failure of a CWS transducer when the CWS mode is engaged.
b) Failure of Air Data Computer, Radio Altimeter, and Instrument Landing System (outer loop) data when the pitch or roll servos are armed.
c) An elevator or aileron servo out-of-detent for more than five seconds when the servos are engaged. d) An automatic stabilizer trim failure when the servos
are engaged. e) An CMD engage inhibit signal when the servos are armed. f) Autopilot in flare mode with only one channel engaged
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