boot inflation, select the brake deice system off. Both
sources of pneumatic bleed air must be in operation
during brake deice system use. Select the brake deice
system off during single engine operation. Circuit
protection is provided by the 5-ampere circuit breaker,
placarded BRAKE DEICE, in the overhead circuit
breaker panel (fig. 2-6).
2-58. FUEL SYSTEM ANTI-ICING.
a. Description. An oil-to-fuel heat exchanger,
located in each engine accessory case, operates
continuously and automatically to heat the fuel
sufficiently to prevent freezing of any water in the fuel.
No controls are involved. Three external fuel vents are
provided on each wing. One is recessed to prevent ice
formation, while the second is flush mounted so that no
ice can collect upon it, the third is electrically heated,
the heating is controlled by the two toggle switches on
the overhead control panel placarded FUEL VENT ON,
LEFT and RIGHT (fig. 2-13). They are protected by the
two 5-ampere circuit breakers, placarded FUEL VENT
HEAT RIGHT LEFT, located in the overhead circuit
breaker panel (fig. 2-6).
electrically heated anti-ice jackets, the
FUEL VENT heat switches should not
be turned ON unless cooling air will
soon pass over the jackets.
b. Normal Operation. For normal operation,
switches for the FUEL VENTS anti-ice circuits are
turned ON as required during the BEFORE TAKEOFF
2-59. WINDSHIELD ELECTROTHERMAL ANTI-ICE
a. Description. Both pilot and copilot windshields
are provided with an electrothermal anti-ice system.
electrothermal anti-ice system. Each system is
comprised of the windshield assembly with heating wires
sandwiched between glass panels, a temperature sensor
attached to the glass, an electrothermal controller, two
relays, a control switch, and two circuit breakers. The
two switches, placarded WSHLD ANTI ICE NORMAL
OFF HI PILOT and COPILOT, respectively, located in
the overhead control panel (fig. 2-13), control system
operation. Each switch controls one electrothermal
windshield system. The circuits of each system are
protected by a 5-ampere circuit breaker and a 50-
ampere circuit breaker, which is not accessible to the
flight crew. The 50-ampere circuit breakers are located
in the power distribution panel under the floor ahead of
the main spar.
b. Normal Operation. Two levels of heat are
provided through the three position switches, placarded
NORMAL, in the aft position, OFF in the center position,
and HI after lifting the switch over a detent and moving
it to the forward position. In the NORMAL position, heat
is provided for the major portion of each windshield. In
the HI position, heat is provided at a higher watt density
to a smaller portion of the windshield. The lever lock
switch feature prevents inadvertent switching to the HI
position during system shutdown.
2-60. PRESSURIZATION SYSTEM.
a. Description. A mixture of bleed air from the
engines, and ambient air, is available for pressurization
to the cabin at a rate of approximately 10 to 17 pounds
per minute. The flow control unit of each engine
controls bleed air from the engine, to make it usable for
pressurization, by mixing ambient air with the bleed air
temperature. On takeoff, excessive pressure bumps are
prevented by landing gear safety switch actuated
solenoids incorporated in the flow control units. These
solenoids, through a time delay, stage the input of
introduction through the left flow control unit first, then 4
seconds later air flow through the right flow control unit.
b. Pressure Differential. The pressure vessel is
designed for a normal working pressure differential of
6.5 PSI, which will provide a cabin pressure altitude of
8,000 feet at an aircraft altitude of 29,700 feet, and a
cabin altitude of 10,000 feet at an aircraft altitude of
c. Pressurization Controller. The pressurization
controller, located in the copilot's subpanel, provides a
display of the selected altitude; an altitude selector, and
a rate control selector. The cabin and aircraft altitude
display is a mechanically coupled dial. The outer scale,
(CABIN ALT) of the display, indicates the selected cabin
altitude; the inner scale (ACFT ALT) indicates the
differential pressure would occur. The