MD Helicopters 369-500, Maintenance Instructions Manual

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CSP-HMI-3
MD Helicopters, Inc
.
MAINTENANCE MANUAL
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[ HMI − 3 Book TOC ]
[ Chapter 97 TOC ]
97-08-00
Page 201
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.
PUBLIC ADDRESS AND SIREN SYSTEM INSTALLATION
MAINTENANCE PRACTICES
1. Description and Operation
(Ref. Figure 201) The public address and siren
system provides the helicopter with an
integral airborne installation consisting of an
audio amplifier, two loudspeakers, a remote
control unit, microphone, system circuit
breaker, three interconnecting wire harness
assemblies, miscellaneous electrical wiring,
and brackets and attachment hardware.
All three wire harness assemblies are attached
to the audio amplifier; one assembly provides
dc power to the amplifier, and the remaining
two assemblies provide dc power from the
amplifier to the control unit and loudspeakers.
The amplifier is installed in the lower electron­
ics compartment under the pilot's compart­
ment floor. The loudspeakers are attached to a
bracket on the exterior of the fuselage, just
forward and below the door on the right side of
the pilot's compartment.
The remote control unit is mounted on the
upper right side of the instrument panel for
access by both the pilot and copilot.
The microphone is attached to a holder on top
of the remote control unit support.
A. Reference Data
Information pertaining to helicopter structural
components which interface with the public
address and siren system installation is in the
Structural Repair Manual (SRM). Refer to
appropriate section for information pertaining
to standard helicopter equipment.
2. Public Address and Siren System Fault
Isolation
Use information provided in Table 201 for
troubleshooting the public address and siren
system installation. For system wiring
diagram, refer to Figure 202.
Table 201. Troubleshooting − Public Address and Siren System
Symptom Probable Trouble Corrective Action
Electrical dc power not available
when system turned on.
No dc power on helicopter main
bus.
Ref. Chap. 96.
Disconnected or defective system
circuit breaker.
Connect or replace circuit breaker as
required.
Fuse blown at amplifier. Replace fuse at amplifier.
Disconnected or defective wire
harness between circuit breaker
and amplifier.
Connect or replace wire harness
between circuit breaker and
amplifier.
Amplifier defective. Replace amplifier.
Circuit breaker trips. Overload or short circuit in system
equipment.
In turn, check loudspeakers, control
unit, and amplifier for short circuits;
also check electrical bond
connections (ground) Sat control unit
and amplifier (Ref. Chap. 96).