MAINTENANCE
Honeywell !!it%h.
2.
B.
(2) Annunciators
The following annunciators indicate IRS status:
ALIGN indicates that the IRU is in the alignment mode.
A
flashing ALIGN annunciator indicates incorrect latitude/longitude
entry, excessive aircraft movement during alignment, or mismatch
between entered and computed latitude.
. ON BATT indicates that backup battery power is being used.
BATT FAIL indicates that backup battery power is inadequate to
sustain IRS operation during backup battery operation (less than
21 volts).
.
FAULT indicates an IRS fault.
(3) Test Mode
. The test mode is selected by pressing the MSU TEST switch or IRU
INTERFACE TEST switch. The test mode can be selected
in
either
the alignment mode or the navigate mode without affecting basic
IRS functions. The test mode is inhibited in the attitude mode,
and in the navigate mode when the aircraft ground speed exceeds
20 knots.
When either switch is pressed, the IRU outputs a preprogrammed
set of fixed digital signals to aircraft instruments.
. The signals are output in three eight-second phases as shown in
Table 2-6.
During the first phase, the IRU exercises all flags
and annunciators. During the second and third phases, the IRU
outputs fixed signals for displays on cockpit instruments. At
the completion of 24 seconds, all outputs return to their
original state.
If either switch is held on, the signals output during the third
phase continue to be output until the switch is released.
22-14-00
Page 118
Aug 15/91
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