CHAPTER 1
UTILITY SYSTEMS
Terminal Objectives: Upon completion of this chapter, you will have a working
knowledge of bleed-air, liquid cooling, windshield wiper/washer, rain repellant,
fire extinguishing, and thermal radiation protection utility systems.
The utility systems of an aircraft provide an
additional measure of flight safety, pilot comfort
and convenience, and contributes to the overall
mission capability of the aircraft. Those utility
systems of primary concern to you that are in-
cluded in this chapter are the various bleed-air,
liquid cooling, fire extinguishing, and thermal
radiation protection systems.
AUXILIARY BLEED-AIR SYSTEMS
Learning Objective: Recognize the
operating principles and functions of
auxiliary bleed-air utility systems.
An aircraft’s auxiliary bleed-air system
furnishes supply air for air-conditioning and
pressurization systems, as well as for electronic
equipment cooling, windshield washing, anti-
icing, and anti-g systems. The bleed-air system
also pressurizes fuel tanks, hydraulic reservoirs,
and radar waveguides on several types of
aircraft.
The air for these systems is tapped off
downstream of the air-conditioning turbine before
any cooling takes place, or at various points within
the air-conditioning system. Bleed air for these
systems can range Up to 400°F (205°C) at
pressures of up to 125 psi. Because each type of
aircraft has a somewhat different approach
in system design, temperatures, and pressures, the
systems and components in this manual will be
representative of types found throughout the
Navy. Under no circumstances should this manual
be regarded as the final source of technical data
used to perform aircraft maintenance. For the
most up-to-date information, refer to the proper
Maintenance Instructions Manual (MIM) for the
system concerned.
WINDSHIELD ANTI-ICE/RAIN
REMOVAL SYSTEM
This system is designed to provide a means
of maintaining visibility from the aircraft.
The F-18 windshield anti-ice/rain removal
system is typical of systems found in jet air-
craft. This system supplies controlled temperature
air from the air cycle air-conditioning system
(ACS) to provide airflow over the external
surface of the windshield for rain removal and
windshield anti-icing.
System Control
The system is electrically controlled and
pneumatically operated. There are three modes
of operation controlled by the windshield anti-
ice/rain removal switch.
1. OFF. The anti-ice/rain removal air control
regulating valve is closed, and there is no airflow
over the windshield.
2. RAIN. Low-pressure (2.5 psig) and low-
volume (20 lbs/min) air at 250°F directed across
the windshield through the anti-ice/rain removal
nozzle.
3. ANTI-ICE. High-pressure (16 psig) and
high-volume (57 lbs/min) air at 250°F directed
across the windshield through the anti-ice/rain
removal nozzle.
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