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
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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 (COLLINS)
DESCRIPTION AND OPERATION
1. Description and Operation
(Ref. Figure 1) The Intercommunication
System (ICS) installation provides the
communications link between helicopter crew
members (pilot, copilot, and observer). In
addition, the crew may monitor signals from
communication and navigation radios, and
may select a COMM transceiver for voice
transmission to other aircraft or ground
stations.
The ICS installation consists of one
C-6533/ARC ICS control panel and one
microphone-earphone headset for each crew
member, and wiring harnesses. The ICS
control panel contains amplifiers for micro­
phone and headset signals, and contains the
necessary switching circuits to provide for
intercommunication (with or without hot mike)
and modulation, monitoring, and control of up
to five transceivers. The ICS control panel has
two basic operating controls:
(1). A rotary switch to select intercom
operation or a particular transmitter,
and
(2). Toggle switches to select any or all of
the various receivers.
Signals from all ICS control panels are
transmitted outside the helicopter. A warning
signal (engine out, low rpm rotor speed) which
cannot be disconnected or varied in volume is
permanently connected to the audio circuit.
A RADIO-ICS rocker switch is located on the
pilot's and copilot's cyclic sticks (Ref. Sec.
67-01). When the switch is pressed to the
RADIO position, radio transmission is enabled;
when pressed to the ICS position, intercom
operation is enabled. The middle (released)
position selects VHF receiver audio, and is the
listening position for interphone and monitor­
ing of the COMM and ADF receivers. A 3
position toggle switch (S305) spring loaded to
the center position is located on the avionics
rack by the observer's ICS control panel. The
operation of this switch is the same as the
RADIO-ICS switches.
Power for the ICS installation is drawn from
the helicopter 28 Vdc bus. Circuit protection is
supplied by 7-1/2 ampere ICS circuit breakers
on the console circuit breaker panel. The
circuit breakers labelled ICS #1 and ICS #2
supply the pilot's and copilot's ICS control
panels, respectively, while the one labelled ICS
#3 supplies the observer's.
NOTE:
For information on any optional radio
installation that is installed and used with
the ICS, refer to the section of this manual
applicable to that specific equipment.
A. C − 6533/ARC ICS Control Panel Controls
and Indicators
(Ref. Figure 1) The ICS control panel is used to
select headphone inputs (receivers) and
microphone outputs (transmitters).
(1). VOL Control:
Adjusts audio level into station head­
set.
(2). Receiver Select Switches:
At the top of the panel, seven toggle
switches provide for individual selection
and mixing of eight audio input lines
from communication and navigation
radios.
NOTE:
Additional audio signals from two direct
(unswitched) lines are continuously moni­
tored. These signals pass directly to the
headsets, and are not affected by the the
VOL control, as are the above.
(3). Transmitter Select Switch:
In the lower center, the six-position
rotary switch provides selection, control
and voice modulation of up to five
transmitters. Selection of a transmitter
automatically causes its associated
receiver to be monitored on the inter­
phone line.
(a). ICS position:
Enables pilot-copilot-observer
intercommunication when rocker
switch on cyclic stick or toggle switch