MD Helicopters 369-500, Maintenance Instructions Manual

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CSP-HMI-3
MD Helicopters, Inc
.
MAINTENANCE MANUAL
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97-04-00
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Neither this document nor any part hereof may be reproduced or transferred to
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purpose except as specifically authorized in writing by MD Helicopters, Inc.
Copyright
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1999 − 2016 by MD Helicopters, Inc.
phone and secondary headphone
outputs are identical. In this mode,
headphone outputs contain 1) the audio
selected by the KMA 24H pushbuttons,
2) engine out and low altitude warn­
ings, and 3) intercom audio from all five
ICS inputs.
(2). Isolate Mode:
When the pilot selects the ISO (Isolate)
mode, he has ``isolated'' himself, that is
taken himself out of the intercom loop
while the other four intercom positions
remain active. The primary headphone
output will contain 1) the audio selected
by the KMA 24H pushbuttons and 2)
engine out and low altitude warnings
only. The secondary headphone output
will contain intercom audio from the
remaining four ICS inputs only. In this
mode, the MIC 2 TX key is disabled
because ICS 2 cannot monitor the
transceivers (single installation only).
(3). Private Mode:
In the PVT (Private) mode of operation,
the pilot and copilot positions are
linked together for two-station hot
mike operation. At the same time, the
other three intercom positions have
independent three-station intercom
operation. The primary headphone
output contains 1) the audio selected by
the KMA 24H pushbuttons, 2) engine
out and low altitude warnings, and 3)
MIC 1 and MIC 2 hot mic audio for
private pilot-to-copilot communica­
tions. The secondary headphone output
contains interphone audio from the
remaining three ICS inputs only.
B. KMA 24H Audio Control Panel Controls
and Indicators
(Ref. Figure 1) Front panel controls include an
interphone volume (VOL) control, two rows of
audio selector pushbuttons, SPKR AUTO
switch, interphone voice-operated intercom
(VOX) control, and a microphone selector (MIC
select) switch.
(1). Audio Selector Pushbuttons:
Each audio selector pushbutton is
push-push, on and off. The top row of
pushbuttons selects the audio to be
heard on the speakers (if installed). The
bottom row of pushbuttons selects the
audio to be heard on the headphones.
The selections are independent of each
other, allowing the same audio input to
be selected for both speaker and
headphones, if desired.
(2). SPKR AUTO Switch:
The SPKR AUTO switch, when pulled
out, automatically selects the audio
from the transceiver selected by the
MIC select switch to be heard on the
cockpit speaker (if installed). The audio
from the transceiver selected by the
MIC select switch is always heard on
the headphones.
(3). MIC Select Switch:
The MIC select switch performs several
functions. It is used to select the
desired transmitter for the cockpit
microphones. It routes microphone
audio and keying to the appropriate
destination, and switches the speaker
amplifier output to the appropriate
speaker (either the cabin, P.A. or
external speaker outputs of the KMA
24H). 8 ohm and 4 ohm taps are
provided on the output of the speaker
amplifier transformer to provide
maximum power transfer.
In the COM positions (1, 2, 3 and 4 for
the -70 unit, 1, 2, 3, 4, and 5 for the -71
unit) of the MIC select switch, micro­
phone audio and keying are routed to
the appropriate transceiver and
transmitted at whatever frequency is
set up on that transceiver, and the
speaker amplifier output is connected
to the cockpit speaker (if installed).
In the PA position, the pilot or copilot
may make announcements to the
passengers provided the helicopter is
equipped with a cabin speaker. The
microphone audio is routed to the
speaker amplifier, microphone keying is
connected to the P.A. mute line, and the
speaker amplifier output is connected
to the passenger address speaker (if
installed).
In the EXT position, microphone audio
is routed to the speaker and amplifier,