Evaporators

T-34C AIRCRAFT SYSTEMS FAMILIARIZATION

CHAPTER TWENTY ONE

WORKBOOK

Compressor

The compressor is a pump that circulates the refrigerant through the system. It is located on the

engine accessory section, left side, and is driven by a belt from the accessory gearbox. A 28

VDC electrically operated clutch allows the pilot to operate the system by engaging or

disengaging the clutch and provides automatic disengagement in the event of system

overpressure or underpressure.

Condenser

A condenser located on the right side of the engine compartment is a heat-exchanging device

used to remove heat from the refrigerant and condense it to a cold liquid. It operates as a

radiator. The refrigerant is received from the compressor and enters the condenser as a high

pressure vapor. Outside air flows through the condenser and removes the heat. The air comes

from two sources; the V-shaped in-flight ram air inlet on the lower right side of the engine

cowling, and a condenser blower inlet located on the right side of the nose landing gear wheel

well. With the gear up, the ram air inlet supplies all required cooling air. With the gear down,

the nose landing gear disrupts airflow into the inlet, resulting in insufficient airflow to the

condenser. To compensate for this air loss, a condenser blower draws air through the screened

condenser blower inlet in the nose landing gear wheel well and blows it through the condenser.

The condenser blower is fan-driven by a 28 VDC motor, and is operated automatically through

the left main gear uplock position switch. The switch closes as the left gear leaves the wheel

well. Air from either source exits the engine compartment through louvers on the cowling.

Evaporators

The cold, liquid refrigerant flows from the condenser to the evaporators. The evaporators are

located in the center console of each cockpit and operate in parallel to remove heat from the

cockpit air. When the system is in operation, the refrigerant flows through each evaporator by

the force of the compressor. Cockpit air flows over the coils by the force of a fan located within

the center console. A drain in the bottom of each console carries away condensation via

individual lines through the bottom of the fuselage.

System Operation

Control of the air conditioning system is provided by a toggle switch and a rheostat located on

each center console. The toggle switch is labeled OFF/FAN/COOL and allows the pilot control

of the fan in the respective cockpit, and the clutch on the compressor. In the OFF position, the

console fan is inoperative and the compressor is disengaged. Selecting the FAN position turns

the respective console fan on while the compressor remains disengaged. In the COOL position

the fan continues to run and the compressor clutch engages. Selecting the COOL position in

either cockpit will engage the compressor clutch. After a 7 to 15 second delay, refrigerated air

will be delivered to each cockpit through the evaporator unit. With the landing gear extended the

COOL position also activates the condenser blower. The AIR rheostat (console fan speed

rheostat) controls the speed of the fan motor in the respective cockpit from minimum to

maximum speed.

AIR CONDITIONING SYSTEM

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