off during single engine operation. Circuit protection is provided by the 5-ampere circuit breaker, placarded BRAKE
2-63. 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 suficiently 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
lush 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 LEFT , RIGHT and ON, (Fig. 2-13). They
are protected by the two 5-ampere circuit breakers, placarded FUEL VENT HEAT LEFT RIGHT, located on the
To prevent overheat damage to 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 procedures.
2-64. WINDSHIELD ELECTROTHERMAL ANTI-ICE SYSTEM.
a. Description. Both pilot and copilot windshields are provided with an electrothermal anti-ice system. Each
windshield is part of an independent 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 WIND-
SHIELD PILOT COPILOT, NORMAL OFF HIGH , respectively, located on 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
light crew. The 50-ampere circuit breakers are located on the power distribution panel under the loor ahead of the
To help prevent windshield cracking, windshield heat should be placed in the NORMAL position for
at least 15 minutes prior to using the HIGH position.
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 HIGH 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 HIGH
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 HIGH position during system shutdown.
2-65. OXYGEN SYSTEM.
a. Description. The cockpit is provided with a quick-donning diluter/demand-type mask, available inside mask
stowage boxes outboard and above each crew station, smoke protection kit, and an oxygen supply panel to turn on
and off the supply of oxygen to the mask. Pilot and Copilot masks are provided with a venting valve, venting oriice
and microphone. The smoke protection kit consists of two smoke goggles to be used with diluter/demand masks by
pilot and copilot.
b. Crew Mask. The crew mask is a quick-donning or o-nasal type that allows oxygen low on demand or under
pressure, as required. The mask is provided with an automatic oxygen dilution system that provides pure oxygen
with cabin altitude over 33000 ft. It can also be manually selected to the 100% position to provide pure oxygen at
all altitudes or to EMERGENCY position to maintain positive pressure in the venting oriice.
c. Smoke Goggles. Smoke goggles were designed for use with crew mask assembly, matching mask face
cone. The venting valve, located on mask shell and manually actuated by user, allows direct communication be-
tween venting oriice and goggles. When mask regulator is selected to emergency position, a metered oxygen low
will be directed to the goggles cavity to allow continuous venting and preventing any iniltration of harmful gases.