TM 1-1520-238-10
2-60
Section IX.
UTILITY SYSTEMS
2.42 DEFOGGING SYSTEM.
The CANOPY DEFOG switch on the pilot ANTI ICE panel
allows the pilot to direct pressurized air (with ECS on or
off) to diffuser outlets at each canopy side panel. When
the CANOPY DEFOG switch is set to ON, 28 vdc from the
No. 1 essential dc bus through the ECS CANOPY ANTI
ICE circuit breaker causes the defog valve to open. This
allows hot air from the pressurized air system to flow
through the shutoff valve to the air mixers. The hot pres-
surized air mixes with the crew station conditioned air in
the air mixers. This partially cooled air is directed against
the canopy side panels to defog them.
PILOT ANTI-ICE PANEL
AUX
ANTI–ICE
ADSS
OFF
STBY FAN
OFF
TADS/PNVS
GND
ON
OFF
W WIPER
CPG
PILOT
CPG AUX / ANTI-ICE PANEL
M01-018
Figure 2-33.
Pilot and CPG Anti-Ice Control Panels
2.43 ANTI-ICING AND DE-ICING.
Multiple anti-icing and de-icing protection is available for
the windshields, pitot tubes, air data sensor, pilot night vi-
sion sensor (PNVS), target acquisition designation sight
(TADS), engine inlets, nose gearboxes, and main and tail
rotor blades. The 30mm weapon and the wing pylons are
also susceptible to icing and may be de-iced by periodic
flexing in azimuth or elevation. The pilot and CPG have
ANTI-ICE panels on their left consoles (fig 2-33).
2.43.1 Windshield Anti-Ice/De-Ice.
The two wind-
shields, one in front, and the other directly above the
CPG, have built-in transparent anti-ice elements that are
heated by 115 vac to prevent ice accumulation. The pilot
activates windshield heating by setting a two-position
CANOPY HTR toggle switch on his ANTI-ICE panel to
ON. In the ON position, the CANOPY HTR switch pro-
vides 28 vdc from the No. 1 essential dc bus through the
CANOPY ANTI-ICE CONTR circuit breaker on the pilot
overhead circuit breaker panel to turn on the windshield
anti-ice control unit. When the control unit is operating,
115 vac from the No. 2 essential ac bus through the CAN-
OPY ANTI-ICE circuit breaker on the pilot overhead circuit
breaker panel is provided to the control unit. The 115 vac
is distributed by the control unit to the window heater ele-
ments. The control unit is provided with temperature con-
trol and fail-safe features. When there is a failure in the
windshield anti-ice system, the control unit will remove the
115 vac power from the unit. If the cause for the failure is
an overheat or false temperature sensor signal, the con-
trol unit can be reset by turning the CANOPY HTR switch
OFF and then back ON. Whenever the control unit, cano-
py heaters, canopy temperature sensors, or input power
fails, or if the canopy overheats with the CANOPY HTR
switch in the ON position, the CANOPY ANTI-ICE FAIL
light on the pilot caution/warning panel will illuminate.
2.43.2 Pitot Tube and Air Data Sensor Anti-Ice/De-
Ice.
The pitot tubes, installed outboard on the leading
edge of both wings, and the air data sensor, attached to
the top of the main rotor de-ice distributor are protected
from ice accumulation by internal heating elements. The
PITOT AD SNSR switch, located on the pilot ANTI-ICE
panel, is a dual function switch. In the ON position, the
right hand pitot heater receives 28 vdc from the emergen-
cy dc bus through the PITOT HTR circuit breaker. The
second function of the switch provides 28 vdc from the No.
3 essential dc bus through the
