T-34C AIRCRAFT SYSTEMS FAMILIARIZATION
System Component Function
The function of each system component in each of the three control lever positions is illustrated
in the table below.
Control Lever Position
Firewall Gate Valve
Bleed Air Regulator
*With the cockpit environmental control lever in the full forward position in the
TEMPERATURE INCREASE range, the butterfly valve is fully closed and the bleed air
regulator is full open. The cockpit will be receiving only bleed air with no outside air mixed.
Overtemperature Warning System
An overtemperature sensor located in the air duct aft of the firewall provides a warning of
overtemperature in the duct area. If the air duct temperature reaches 250° F, an electrical signal
from the sensor will cause the MASTER CAUTION and BLEED AIR annunciator fault light in
each cockpit to illuminate. Placing the environmental control lever in FRESH AIR INCREASE
should extinguish the lights.
Aft Cockpit Ventilation
In addition to the ventilation provided by the cockpit environmental control system, the aft
cockpit can receive additional outside fresh air via a ram air inlet on the underside of the fuselage
(beneath the front cockpit) which directs ram air to the air outlets on the center console in the aft
cockpit. Control of the system is provided through a push-pull knob on the aft cockpit center
console labeled OUTSIDE AIR, PULL ON. With the knob pushed in, no air flows from the air
outlets. Pulling the knob to ON opens a valve and air flows from the air outlets. Air flow and
direction is controlled by the louvers on the air outlets. The center console also houses the
evaporator for the air conditioning system. If the air conditioning system is on, the outside air
entering this system is also cooled.
Windshield Defogging System
A WINDSHIELD DEFOGGER control lever located above the cockpit environmental control
lever provides the pilot in the front cockpit with control of air flow to remove condensation from
the inside surface of the windshield. The lever controls the defogger valve located aft of the
firewall in the cockpit air ducting. In the OFF position the valve is closed and no air flows.
Forward movement of the lever progressively toward MAX opens the valve to permit increasing
air flow to the windshield. The most effective windshield defogging is achieved with the
defogger control at MAX and the cockpit environmental control in the TEMPERATURE
20-4 COCKPIT HEATING, VENTILATING, AND WINDSHIELD DEFOGGING SYSTEM