SECTION IX. UTILITY SYSTEMS
2-54. DEFROSTING SYSTEM.
a. Description. The defrosting system is an integral part of the heating and ventilation system. The system
consists of two warm air outlets connected by ducts to the heating system. One outlet is just below the pilot s wind-
shield and the other is below the copilot s windshield. A push-pull control, placarded DEFROST AIR , on the pilot s
subpanel, manually controls airlow to the windshield. When pulled out, defrosting air is ducted to the windshield.
As the control is pushed in, there is a corresponding decrease in airlow.
b. Automatic Operation.
1. VENT BLOWER switches -- As required.
2. CABIN AIR MODE SELECT switch -- AUTO.
3. CABIN AIR TEMP CONTROL rheostat -- As required.
4. CABIN AIR , COPILOT AIR , PILOT AIR , and DEFROST AIR controls -- As required.
c. Manual Operation. If the automatic temperature control should fail to operate, the temperature of defrost air
and cabin air can be controlled manually by setting the CABIN AIR MODE SELECT switch to the MANUAL COOL
position, then using the CABIN AIR TEMP CONTROL switch to set the desired temperature. This control is located
1. PILOT and COPILOT AIR controls -- In.
2. CABIN AIR and DEFROST AIR controls -- Out.
3. CABIN AIR MODE SELECT switch -- MAN COOL.
4. Cold air outlets -- As required.
5. CABIN AIR MANUAL TEMP switch -- As required.
2-55. SURFACE DEICING SYSTEM.
a. Description. Ice accumulation is removed from each inboard and outboard wing leading edge; horizontal
stabilizers, stabilons, and tailets by the lexing of deice boots which are pneumatically actuated. Engine bleed air
from the engine compressor is used to supply air pressure to inlate the deice boots, and to supply vacuum through
the ejector system. A pressure regulator protects the system from over inlation. When the system is not in operation,
a distributor valve keeps the boots held down by vacuum supplied through the ejector system.
Operation of the surface deice system in ambient temperatures below -40° C can cause permanent
damage to the deice boots.
Under conditions where one bleed air source is inoperative, suficient bleed air pressure for deice
inlation may not be available. Prior to deice boot inlation, check the regulated air pressure gauge
for a minimum of 16 PSI. If insuficient pressure exists, increasing engine N 1 and/or decreasing
altitude will increase bleed air pressure.