TM 1-1510-223-10
Table 3-7. VHF Navigation Receiver Fault Codes
CODE
INCORPORATION
COMMENT
00
No fault found
02
RAM test failed
Unit unusable (mP problem)
03
No serial data to unit
Unit unusable (CTL problem)
04
No serial freq word
Unit unusable (CTL problem)
05
Invalid NAV freq
CTL may be tuned to DME channel
06
Microprocessor fault
Unit unusable
09
Microprocessor fault
Unit unusable
10
Microprocessor fault
Unit unusable
11
AID fault
Unit unusable
12
A/D failed accuracy test
Unit unusable
13
+13 V dc power supply fault
Unit unusable
14
-13 V dc power supply fault
Unit unusable
15
VOR sin e / GS D/A fault
VOR/LOC unusable
16
VOR cos 6 /GS D/A fault
VOR/GS unusable
17
VOR smo unlocked
VOR receiver imperative
18
VOR AFC not locked
VOR unusable (no rf signal)
19
Low 30 Hz reference signal
VOR unusable
20
Low 30 Hz variable signal
VOR unusable
21
400 Hz pwr supply unusable
VOR OBI and OBS unusable
22
OBI sin out of tolerance
VOR OBI and OBS unusable
23
OBI cos out of tolerance
VOR OBI and OBS unusable
24
OBS return out of tolerance
VOR OBS unusable
25
LOC smo unlocked
LOC receiver inoperative
26
LOC signal level low
LOC unusable
27
LOC dev out of tolerance
LOC dev unreliable
28
GS smo unlocked
GS receiver inoperative
29
GS signal too low
GS unusable
30
GS dev out of tolerance
GS dev unreliable
32
Marker beacon fault
Observe marker lamps for fault
BTO3844
(9) Power and mode switch. The power and
mode switch contains four detented positions placarded
OFF, ANT, ADF, and TONE The OFF position removes
system power. Selecting ANT, ADF, or TONE position
applies power to the ADF system and establishes the
system mode of operation.
(10)
Annunciators. The receiver control unit
contains a MEM (memory) and a RMT (remove)
annunciator.
The
MEM
annunciator
illuminates
whenever a preset frequency is being displayed in the
lower window. The RMT annunciator is not used in this
installation.
(11)
Preset frequency display. The preset
(inactive)
frequency
and
diagnostic
messages
are
displayed in the lower window.
(12)
Compare annunciator. An annunciator
placarded ACT momentarily illuminates when frequencies
are being changed. The ACT annunciator flashes if the
actual radio frequency which the receiver is tuned to is
not identical to the frequency shown in the active
frequency display.
c.
Operating Procedures.
It is not practical to provide monitoring for all
conceivable system failures and, it is possible
that erroneous operation could occur without a
fault indication. It is the responsibility of the
pilot to detect such an occurrence by means of
cross-checks
with
redundant
or
correlated
information available in the cockpit
(1) Equipment turn on. The ADF receiver and
the control unit are turned on by rotating the power and
mode switch on the ADF control unit to the ANT, ADF, or
TONE position After power is applied, the control unit
displays the same active and preset frequencies that were
present when the equipment was last turned off.
(2) Frequency selection. Frequency selection is
made using either the frequency select knobs or the XFR/
MEM (transfer/memory recall switch).
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