MD Helicopters 369-500, Maintenance Instructions Manual

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CSP-HMI-3
MD Helicopters, Inc
.
MAINTENANCE MANUAL
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97-02-00
Page 101
Revision 12
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1999 − 2016 by MD Helicopters, Inc.
INTERCOMMUNICATION SYSTEM (COLLINS)
TROUBLESHOOTING
1. Intercommunication System
Troubleshooting
Special Tools
(Ref. Section 91 − 00 − 00)
Item Nomenclature
ST1010 Volt-ohmmeter
A. General
When equipment malfunctions during helicop­
ter operation, the equipment should be tagged
to indicate the exact nature of the malfunction
and the operating mode(s) in which it occurred.
(1). Always talk to the pilot who last flew
the helicopter first, to obtain any
information he may be able to provide
about the nature of the malfunction.
(2). If the type of malfunction is unknown,
perform an operational check, operating
the equipment in all normally used
modes to determine the type of fault
(Ref. Table 101, and Intercommunica­
tion System Operational Checks.
(3). Visually inspect for possible causes of
malfunctions and for damage and
deterioration that can be repaired to
prevent future trouble.
(4). Parts of assemblies found to be defec­
tive should be removed and either
repaired or replaced.
(5). If it is not obvious whether a fault
symptom is caused by the ICS or a
radio, fault isolation is still possible by
probing signal lines between the ICS
and radio installations with a digital
multimeter (ST1010).
Ensure that helicopter power is
OFF before probing with the
ohmmeter (next step).
(a). First perform a continuity check of
the loop where the suspected mal­
function occurs (Ref. Figure 101 and
the wiring diagrams in the sections of
this manual which pertain to the
radio equipment in your helicopter).
NOTE:
Coaxial cables are the most likely items
to fail.
(b). Turn on helicopter power and ener­
gize the ICS and one radio (fault
isolation is easier if equipment not
being analyzed is off). Troubleshoot
each radio as instructed (Ref. ``Trans­
mit'' and ''Receive'' Problems).
NOTE:
Troubleshoot a ``transmit'' problem by
probing at the headset and working back­
wards toward the radio. Troubleshoot a ``re­
ceive'' problem by probing at the audio out­
put of the radio and working forwards
toward the headset.
B. Transmit and Receive Problems
The selection, control and audio signals are all
routed thru terminal boards TBM300-1 thru
-8 (Ref. Chap. 96 for terminal board locations).
NOTE:
Optional avionic equipment installa­
tion combinations vary with each operator.
Up to seven audio inputs (Receiver Select
Switch - positions 1 thru 5, AUX and NAV))
and five transmitter outputs (Transmitter
Select Switch - positions 1 thru 5) may be
used, if needed, to interface various avionic
equipment installations.
(1). The receiver select switch labels on the
ICS control panel (Ref. Figure 1)
correspond to signal nomenclature on
the wiring diagram (Ref. Figure 101).
There are five receiver select toggle
switches, for example, labelled 1 thru 5.
CAUTION