MD Helicopters 369-500, Maintenance Instructions Manual

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CSP-HMI-3
MD Helicopters, Inc
.
MAINTENANCE MANUAL
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Revision 7
95-00-00
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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.
(4). (Ref. Figure 501) Current model
(Rochester) instrument clusters
(369D296305) use +28 Vdc from the
helicopter electrical system. Voltage-
dropping resistors are not used on
Slim-Line instrument panels. On R/H
command T-Panels, voltage-dropping
resistor R112 is used to 28 Vdc
power to meet internal lamp require­
ments. Ammeter deflection results from
input millivolt flow through helicopter
3-10 wiring.
D. Ammeter Description (369E/FF − 500N)
The ammeter is a millivolt meter which
measures current flow through helicopter
wiring. Pointer deflection is proportional to
current flow.
E. Dual Volt / Amp Indicator Description
(600N)
The voltmeter indicates voltage present at the
generator. The ammeter monitors the current
load on the generator by sensing voltage drops.
The indicator is an internally lighted instru­
ment.
F. Engine Oil Temperature Gauge
Description
The engine oil temperature gauge indicates
engine oil temperature in degrees centigrade.
The engine oil temperature sender functions
as a variable resistance leg of the indicator
bridge circuit. As temperature changes,
resistance within the sender changes causing
an imbalance in current flow through instru­
ment windings to move the gauge pointer.
G. Fuel Quantity Gauge Description
(369D/E/FF − 500N)
The fuel quantity gauge indicates the remain­
ing operating fuel weight in hundreds of
pounds (pounds x 100). The tank sending unit
(Ref. Chap. 28) functions as the variable
resistance leg of the indicator bridge circuit. As
fuel level changes (sensed by float arm
position), resistance within the sending unit
changes, causing an imbalance in current flow
through instrument windings to move the
gauge pointer.
H. Fuel Quantity Indicator Description
(600N)
The fuel quantity indicator receives data from
two fuel probes located within the fuel cell.
These probes sense the level and temperature
of the fuel in the cell and transmits electrical
signal information to the fuel quantity
indicator.
I. Caution and Warning Indicator Lights −
General
The caution and warning lights indicating
system includes the following components.
(1). Slim-Line instrument panels only:
Nine indicator lights and a PRESS-
TO-TEST pushbutton across the top of
the instrument panel. Two additional
indicator lights are located in the
warning horn housing above the panel.
(2). R/H command T-Panels only:
Eleven indicator lights and a PRESS-
TO-TEST pushbutton at the top of the
panel under the panel hood. An option­
al spare light position is provided.
(3). L/H command T-Panels only:
Twelve indicator lights and a PRESS-
TO-TEST pushbutton at the top of the
panel under the panel hood. Three
optional spare light positions are
provided.
(4). Senders, detectors and switches
associated with the light indicators.
(5). An Autronics Indicator Lights Dimmer
Assembly (dimming unit) provides light
test circuits and a switching regulator
for panel and instrument light dimming
and relay for dimming caution lights.
(6). An Autronics Engine Power Out (EPO)
Warning Control Unit (EPO warning
control unit) that includes an integral
audio amplifier.
(7). The indicators are legend-type signal
lights and are interconnected with the
PRESS-TO-TEST pushbutton switch
and a solid-state dimmer assembly
that isolates light test circuits from
operational circuits. With power on, and
engine not running, the red engine