MD Helicopters 369-500, Maintenance Instructions Manual

Page: 661 / 722

CSP-HMI-3
MD Helicopters, Inc
.
MAINTENANCE MANUAL
[ Main Menu ]
[ HMI − 3 Book TOC ]
[ Chapter 97 TOC ]
97-04-00
Page 101
Revision 12
The information disclosed herein is proprietary to MD Helicopters, Inc.
Neither this document nor any part hereof may be reproduced or transferred to
other documents or used or disclosed to others for manufacturing or any other
purpose except as specifically authorized in writing by MD Helicopters, Inc.
Copyright
©
1999 − 2016 by MD Helicopters, Inc.
INTERCOMMUNICATION SYSTEM (KING)
TROUBLESHOOTING
1. Intercommunication System
Troubleshooting
(Ref. Figure 101 or Figure 102 and Table 101)
2. KMA 24H Audio Control Panel
Troubleshooting (Dual Installations)
Dual KMA 24H installations require some
special considerations for optimum perform­
ance. A possibility of audio feedback exists
when either panel has transceiver audio
selected for its cockpit speaker. This is because
the microphone for one audio panel may pick
up the nearby cockpit speaker audio of the
other audio panel, and when these audios are
the same feedback can occur. This condition
only exists while simultaneously transmitting
on a transceiver thru one audio panel, and
monitoring the audio of the same transceiver
(sidetone) on the speaker of the other panel.
The feedback can be minimized by the use of
high quality noise-cancelling microphones,
and by reducing the sidetone volume of the
receivers. However, if the feedback is still
objectionable, several techniques can be used
to avoid possible feedback situations entirely.
The most obvious is to never select any of the
three transceiver audio inputs for the cabin
speakers. This is not a desirable solution,
however, unless headphones are used exclu­
sively. Probably the best method is to use the
SPKR AUTO switch on the KMA 24H to select
the transceiver audio input for the speaker.
When SPKR AUTO is selected on one or both
panels for the speaker audio, and no other
transceiver audios are selected on either panel,
the situation required for feedback will not
occur. The source of speaker audios will then
track the position of the MIC select switches.
When the MIC select switches of both panels
are set to the same transceiver position, both
panels will mute their speakers when either
microphone is keyed.
Table 101. Troubleshooting ICS System
Symptom Probable Cause Corrective Action
WARNING: Before removing or installing components connected to the electrical system, ensure that
all electrical power is OFF. If units are not immediately replaced, ensure that all electrical connectors
are suitably capped and stowed and all loose cable ends are properly insulated to prevent the
possibility of shorting. Serious injury or death could result from voltages present in the electrical
system.
NOTE:
The following general troubleshooting information also applies to other avionics installations that may be
in the helicopter, since a trouble in equipment in one installation that is commonly used by other installations
can cause a symptom with associated installations. Disregard information that pertains to equipment or instal-
lations that are not installed.
GENERAL
No dc power to equipment of an
installation.
Defective associated circuit
breaker.
Replace circuit breaker.
No dc power on helicopter main dc
bus.
(Ref. Sec. 96 − 00 for electrical
system fault isolation)
Circuit breaker trips. Overload or short circuit in
equipment of associated
installation.
Isolate to the specific installation;
then troubleshoot the installation.