MD Helicopters 369-500, Maintenance Instructions Manual

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CSP-HMI-3
MD Helicopters, Inc
.
MAINTENANCE MANUAL
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[ Chapter 97 TOC ]
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Revision 12
97-04-00
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.
mute output is provided to mute passenger
background music systems when the MIC
select switch on the KMA 24H front panel is in
the PA position and a microphone is keyed.
A headset-microphone (Ref. Sec. 97-01) is
located at each intercom station. Headset-mi­
crophones at the center front, left rear and
right rear positions interface with the ICS by
means of an adaptor, which is a headset switch
and jack assembly (switch/jack) containing a
RADIO-ICS switch. The middle (released)
switch position selects vhf receiver audio and
is the listening position for interphone and
monitoring the vhf COMM, vhf NAV, DME,
MKR and ADF receivers. Voice transmission
over the interphone from an intercom station
is selected by pressing the switch/jack at that
station to the ICS position. Pressing the
switch/jack to the RADIO position has no
effect. Switch/jacks are removed by disconnect­
ing them at the bulkhead headset connectors.
The pilot's and copilot's headset-microphones
do not require adaptors to interface with the
ICS. The installed pilot's and copilot's headset
jacks contain a phone jack that mates with a
standard U-174/U interphone plug connected
to the ICS control unit via helicopter wiring.
At the pilot's and copilot's positions, a RADIO-
ICS switch on the cyclic stick (Ref. Sec. 67-10)
is used in conjunction with the headset-micro­
phone. Pressing the switch to the ICS position
selects voice transmission over the interphone.
Pressing the switch to the RADIO position
keys the transmitter of the selected vhf COMM
transceiver. The middle (released) position of
the switch selects vhf receiver audio, and is the
listening position for interphone and monitor­
ing of the radios.
The copilot's radio footswitch (Ref. Figure 2)
enables the copilot to transmit without having
to press the rocker switch on the cyclic stick to
the RADIO position.
There is no power on-off switch on the KMA
24H. The unit operates on two +28 Vdc inputs
from the helicopter main bus. The first input is
supplied by either the AUDIO circuit breaker
(CB209, LH command helicopters) or the ICS
circuit breaker (CB112, RH command helicop­
ters); this input powers the two headphone
amplifiers. The second input is supplied by the
EMER AUD (or EMERG ICS) circuit breaker
(CB208 on LH command helicopters, CB121 on
RH command helicopters); this input powers
the speaker amplifier. With the unit wired in
this manner, emergency operation is provided
as follows:
(1). The EMG position of the KMA 24H
MIC select switch connects the MIC,
key and primary headphone outputs
directly to the COM 1 (Ref. Para. KMA
24H Audio Control Panel Controls and
Indicators below).
(2). If the primary headphone output fails,
the secondary headphone output may
still operate and provide full audio
selection.
(3). If both headphone amplifiers fail, an
emergency phone jack, if wired, can
provide full audio selection thru the
speaker amplifier.
The panel lighting is powered by the
helicopter light dimmer.
NOTE:
For information on any optional avion­
ics equipment that is installed and used
with the ICS, refer to the section of this
manual applicable to that specific equip­
ment. For additional information on the
KMA 24H audio control panel, refer to the
manufacturer's publication (Ref. Table 201,
Sec. 01-00).
A. Modes of Operation (Helicopters with
Optional INTERCOM Mode Select Switch
Only)
In helicopters with the three-position INTER­
COM mode select switch installed (Ref.
Figure 2), the headphone outputs depend on
what mode of operation the pilot has selected.
There are three modes of operation: Normal,
Isolate and Private. (Ref. Figure 3 for a chart
showing the audio presented to the primary
and secondary headphones in each mode; note
that the mode selected has no effect on speaker
audio.)
NOTE:
In the following paragraphs, reference
is made to a low altitude warning signal.
This signal is available only if a radar altim­
eter is installed in the helicopter.
(1). Normal Mode:
In the NORM (Normal) mode of
operation, all five intercom positions
are tied together. The primary head­