During normal operation of the anti-icing system,
all four-engine bleed air valves are open to supply bleed
air to the cross-ship manifold, and both fuselage bleed
LEARNING OBJECTIVE: Recognize the
air shutoff valves are closed. The modulating valves,
components and operating principles for a
which are controlled by pneumatic thermostats,
windshield anti-ice/rain removal system.
maintain a controlled flow of bleed air to the leading
This system is designed to provide a means of
edge distribution system. The complete system is
maintaining visibility from the aircraft. The F-18
monitored for hot spots by heat-sensing switches.
windshield anti-ice/rain removal system is typical of
systems found in jet aircraft. This system supplies
Before flight, the anti-icing manifold system may
controlled temperature air from the air cycle
be tested for leakage. This leak test is performed by
air-conditioning system (ACS) to provide airflow over
pressurizing the system: OPEN the No. 4 engine bleed
the external surface of the windshield for rain removal
air valve; the Nos. 1, 2, and 3 engine bleed air valves
and windshield anti-icing.
remain CLOSED, and both fuselage shutoff valves are
in the OPEN position. When the bleed air pressure on
the bleed air manifold reads 70 psi, the No. 4 engine
Components of the windshield anti-ice/rain
bleed air valve is closed and the leak test switch is
removal system include a warm air temperature control
actuated. As the bleed air pressure drops, the
valve, temperature sensors, a flow/temperature limiting
time-delay relay will illuminate the ACCEPT light after
anti-ice modulating valve, an air control regulating
an 8-second delay if the system is tight. The light will
valve, and an anti-ice/rain removal switch.
go out when the test switch is released.
Warm Air Temperature Control Valve
Q5-7. Describe the difference between an anti-icing
The warm air temperature control valve operates to
system and a deicing system.
control temperature entering the windshield anti-ice
Q5-8. In an anti-ice system, what method(s) are
and rain removal ducts. The valve is modulated by
used to remove ice formation?
muscle pressure, which is controlled by the warm air
Q5-9. Identify the four major components of a P-3
Warm Air Temperature Sensor
The OPEN light on the ice protection panel
The warm air temperature sensor (fig. 5-7, item A)
will illuminate when what condition occurs?
is located downstream of the warm air temperature
Figure 5-7.--Windshield anti-ice and rain removal system component locator.