ture (of defrost air and cabin air) may be controlled
manually by manipulating the CABIN TEMP MODE
control switch between the OFF and MAN HEAT
2-52. SURFACE DEICER SYSTEM.
Description. Ice accumulation is removed from
each inboard and outboard wing leading edge, and both
horizontal stabilizers by the flexing of deicer boots which
are pneumatically actuated. Engine bleed air, from the
engine compressor, is used to supply air pressure to
inflate the deicer boots, and to supply vacuum, through
the ejector system, for boot hold down during flight. A
pressure regulator protects the system from over inflation.
When the system is not in operation, a distributor valve
applies vacuum to the boots for hold down.
Operation of the surface deice
system in ambient temperatures
below -40°C can cause permanent
damage to the deice boots.
Deice boots are intended to remove ice
after it has formed rather than prevent its formation. For
the most effective deicing operation, allow at least 1/2
inch of ice to form on the boots before attempting ice
removal. Very thin ice may crack and cling to the boots
instead of shedding.
Never cycle the system rapidly, this
may cause the ice to accumulate
outside the contour of the inflated
boots and prevent ice removal.
A three position switch on the overhead
control panel placarded DEICE MANUAL OFF SINGLE
CYCLE AUTO, controls the deicing operation. The switch
is spring loaded to return to the OFF position from
SINGLE CYCLE AUTO or MANUAL. When the SINGLE
CYCLE AUTO position is selected, the distributor valve
opens to inflate the wing boots. After an inflation period
of approximately 6 seconds, an electronic timer switches
the distributor to deflate the wing boots and a 4 second
inflation begins in the horizontal stabilizer boots. When
these boots have inflated and deflated, the cycle is
If the switch is held in the MANUAL
position, the boots will inflate simultaneously and remain
inflated until the switch is released. The switch will return
to the OFF position when released. After the cycle, the
boots will remain in the vacuum hold down condition until
again actuated by the switch.
Either engine is capable of providing
sufficient bleed air for all requirements of the surface
deicer system. Check valves in the bleed air and vacuum
lines prevent backflow through the system during single-
engine operation. Regulated pressure is indicated on a
gage, placarded PNEUMATIC PRESSURE, located on
the copilots subpanel.
2-53. ANTENNA DEICE SYSTEM.
Description. The antenna deice system removes
ice accumulation from the inboard wing dipole antennas
and the aft rotating boom dipole antenna. Pressure
regulated bleed air from the engines supplies pressure to
inflate the boots. To assure operation of the system in the
event of failure of one engine, a check valve is
incorporated in the bleed air line from each engine to
prevent loss of pressure through the compressor of the
inoperative engine. Inflation and deflation phases are
controlled by a distributor valve. Deice boots are
intended to remove ice after is has formed rather than to
prevent it's formation. For the most effective deicing
operation, allow at least 1/8 to 1/4 inch of ice to form on
the boots before attempting ice removal. Very thin ice
may crack and cling to the boots instead of shedding.
Never cycle the system rapidly.
accumulate outside the contour of
the inflated boots and prevent ice
Antenna Deice System Switch. The antenna
deice system is controlled by a switch placarded ANT
DEICE, SINGLE-OFF-MANUAL located on the overhead
control panel (fig. 2-18). The switch is spring loaded to
return to the OFF position from the SINGLE or MANUAL
position. When the switch is set to the single position, the
system will run through one timed inflation-deflation cycle.
When the switch is held in the MANUAL position the
boots will inflate and remain inflated until the switch is
Forward Wide Band Data Link Antenna Radome
Anti-Ice. The forward wide band data link antenna
radome anti-ice system utilizes engine bleed air to