CSP−900RMM−2MD Helicopters, Inc.
Rotorcraft Maintenance Manual
Page 1
Original
21-40-00
HEAT / DEFOG SYSTEM
DESCRIPTION AND OPERATION
1. Heat / Defog System
The heat/defog system supplies heated air to
the cabin and crew area, and provides heated
air for defog purposes. Compressor bleed air
from both engines is used for heat and defog.
In case of an engine failure the heat/defog is
automatically shutoff through the Integrated
Instrument System (IIDS). The heat/defog can
be reactivated by placing the CAB HEAT
switch on the center console utility panel to
the OVRD position. When a fire/overheat
bleed air leak indication CAB HEAT appears
on the IIDS, the IIDS will automatically
shutoff the heat/defog system. The heat/defog
system consists of:
Engine Bleed Air Check Valve - Prevents
reverse flow of bleed air.
Flow Control Shutoff Valve - Provides crew
member control of bleed air to the heat/defog
system.
Heat Flow Control Valve - Controls the flow
of bleed air to the aft cabin heater ejector.
Heater Control Cable - Mechanically
controls heat flow control valve position.
Aft Cabin Heater Ejector - Mixes bleed air
with ambient cabin air and releases the mixed
air to the cabin compartment.
Heat/Defog Bleed Air Lines - Routes bleed
air to the flow control valves.
Heat/Defog Valve - Controls the flow of bleed
air to the heat/defog ejector.
Heat/Defog Control Cable - Controls heat
defog valve position.
Heat/Defog Ejector - Mixes ambient cockpit
air with bleed air.
Defog Manifolds - Releases heated air to the
wind screens for defog purposes.
Foot Heater Valve - Releases heated air to
the crew compartment.
Foot Heater Control Cable - Controls foot
heater valve position.
A. Engine Bleed Air Check Valve
The engine bleed air check valve is an in-line
check valve that prevents reverse flow of bleed
air into the engine compressor of a failed
engine. The bleed air check valve attaches to
the bleed air fitting.
B. Flow Control Shutoff Valve
The flow control shutoff valve is a normally
closed solenoid valve constructed of stainless
steel. The valve is located at the intersection of
the compressor bleed air lines from both
engines. The valve is electrically activated by
the pilot to control the flow of compressor bleed
air to the heat/defog system.
C. Heat Flow Control Valve
The heat flow control valve is a stainless steel
single ball valve. The valve is located on the
aft cabin heat ejector. The valve is activated
mechanically for controlling the flow of bleed
air entering into the aft cabin heater ejector.
D. Heater Control Cable
The heater control cable is located in the aft
passenger compartment. The cable is a push
pull cable constructed of stainless steel. The
cable adjusts the heat flow control valve.
E. Aft Cabin Heat Ejector
The aft cabin heater ejector is located in the
aft passenger compartment. The ejector acts
like a flow divider mixing inside ambient cabin
air with hot engine bleed air to produce heated
cabin air.
F. Heat / Defog Bleed Air Tubes
The heat/defog bleed air tubes are stainless
steel tubes that route bleed air throughout the
heat/defog subsystem. The tubes route bleed
air to the heat flow control valve, heat/defog
valve, and foot heater valves.
G. Heat / Defog Valve
The heat/defog valve is a stainless steel ball
valve located at the lower left cockpit fuselage
section. The valve is mechanically activated to
route bleed air into the heat/defog ejector for
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