position, the system will run through one timed inlation-delation cycle. When the switch is held in the MANUAL
position, the boots will inlate and remain inlated until the switch is released.
c. Operation. 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 1/8 to 1/4 inch of ice to form on the boots before attempting the
removal. Very thin ice may crack and cling to the boots instead of shedding.
2-57. FORWARD GUARDRAIL DUAL DATA LINK ANTENNA RADOME ANTI-ICE.
The forward guardrail dual data link (GDDL) antenna radome anti-ice system utilizes engine bleed air to prevent the
formation of ice on the radome. A switch, placarded RADOME - controls the system ON , located on the overhead
control panel (Fig. 2-13). The circuit is protected by a 7.5-ampere circuit breaker, placarded RADOME ANTI-ICE ,
2-58. PROPELLER ELECTRIC DEICE SYSTEM.
a. Description. The propeller electric deice system includes: electrically heated deice boots, slip rings and
brush block assemblies, ammeter, and a timer for automatic operation. Circuit breakers (Fig. 2-12), placarded
PROP ANTI-ICE, MANUAL AUTO provide circuit protection for left and right propeller. Two switches located on
the overhead control panel (Fig. 2-13), placarded PROP , AUTO MANUAL , ON , provide automatic or manual
control of the system.
b. Automatic Operation. The two-position switch located on the overhead control panel, placarded PROP
AUTO - ON , is provided to activate the automatic system. Upon placing the switch to the ON position the timer
diverts power through the brush block and slip ring to all heating elements on one propeller. Subsequently, the timer
then diverts power to all heating elements on the other propeller for the same length of time. This cycle will continue
as long as the switch is in the ON position. The system utilizes a metal foil type single heating element, energized
by DC voltage. The timer switches every 90 seconds, resulting in a complete cycle in approximately 3 minutes.
The spring-loaded control switch located on the overhead control panel, placarded PROP - MANUAL - ON , and
controls the manual override relay. When holding the switch in the ON position the automatic timer is overridden,
and power is supplied to the heating elements of both propellers simultaneously. This switch is of the momentary
type and must be held in position for approximately 90 seconds to dislodge ice from the propeller surface. Repeat
this procedure as required to avoid signiicant buildup of ice, which will result in a loss of performance, vibration, and
system is being utilized in the manual mode. However, each load meter will indicate an approximate 10% increase
in load while the manual prop deice system is operating.
Pitot heat should not be used for more than 15 minutes while the aircraft is on the ground. Over-
heating may damage the heating elements.
2-59. PITOT HEAT SYSTEM.
Heating elements are installed in both pitot masts, located on the nose. Each heating element is controlled by an
individual switch placarded PITOT , LEFT , RIGHT and ON , located on the overhead control panel (Fig. 2-13).
Circuit protection is provided by the two 7.5-ampere circuit breakers placarded PITOT HEAT on the overhead circuit
breaker panel (Fig. 2-12). The true airspeed temperature probe heat control circuit is also protected by this circuit
breaker. If either left or right pitot heat is on, the true airspeed temperature probe heat will be on.