TM 55-1510-221-10
Operation of the surface deice system in
ambient temperatures below -40°C can
cause permanent damage to the deice
boots.
b. Operation.
(1.) Deice boots are intended to remove
ice after it has formed rather than prevent its forma-
tion. For the most effective deicing operation, allow
at least l/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.
NOTE
Never cycle the system rapidly, this may
cause the ice to accumulate outside the
contour of the inflated boots and prevent
ice removal.
(2.) A three position switch on the over-
head control panel placarded SURF DEICE MAN-
UAL - 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 horizon-
tal stabilizer boots. When these boots have inflated
and deflated, the cycle is complete.
(3.)
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.
(4.)
Either engine is capable of providing
sufficient bleed air for all requirements of the sur-
face 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 PRES-
SURE, located on the copilots subpanel.
2-52. ANTENNA DEICING SYSTEM.
a.
Description. The antenna deice system
removes ice accumulation from the dipole mission
2-42
antennas. The system consists of two ejector distrib-
utor valves, a regulator, manifold, and flexible tub-
ing. Control is accomplished through a timing cir-
cuit and an antenna deice switch located on the
overhead control panel (fig. 2-12). Erosion resistant
tape is applied to the surface of mission blade anten-
nas not having deice boots.
b.
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. 2-12). 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 released.
c. 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 prevent the formation of ice on the radome.
The system is controlled by a switch placarded
RADOME located on the overhead control panel.
The circuit is protected by a circuit breaker plac-
arded RADOME, located on the overhead circuit
breaker panel (fig. 2-26).
d. Operation.
(1.) Deice boots are intended to remove
ice after it has formed rather than prevent its forma-
tion. For the most effective deicing operation, allow
at least l/8 to l/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.
NOTE
Never cycle the system rapidly, this may
cause the ice to accumulate outside the
contour of the inflated boots and prevent
ice removal.
2-53. PROPELLER ELECTROTHERMAL ANTI-ICE
SYSTEM.
a.
Description. Electrothermal anti-ice boots
are cemented to each propeller blade to prevent ice
formation or to remove the ice from the propellers.
Each thermal boot consists of one outboard and one
inboard heating element, and receives electrical
power from the deice timer. This timer sends cur-
rent to all propeller deice boots and prevents the
boots from overheating by limiting the time each
element is energized. Four intervals of approxi-
mately 30 seconds each complete one cycle. Current