Cockpit Environmental Control Lever

T-34C AIRCRAFT SYSTEMS FAMILIARIZATION

CHAPTER TWENTY

WORKBOOK

Cockpit Environmental Control Lever

The cockpit environmental control lever is located in the front cockpit only on the upper forward

portion of the left sidewall. It provides the pilot in the front cockpit with control of fresh and

heated air flow in both cockpits. The control consists of a slide assembly and three individual

control cables which control the bleed air regulator, the butterfly valve in the jet pump assembly

and the firewall gate valve. The cockpit environmental control has an OFF position and two

ranges--FRESH AIR INCREASE and TEMPERATURE INCREASE. In the OFF position, no

fresh outside or heated air enters the cockpit. As the control is moved forward into FRESH AIR

INCREASE, fresh air flow from the cockpit outlets increases. Movement into the

TEMPERATURE INCREASE range progressively increases the temperature of the air from the

cockpit outlets.

System Components

The engine bleed air regulator is located on the left side of the engine compartment. It provides

volume control of engine (diffuser) bleed air flow. A corrugated metal tube carries bleed air

from the bleed air tap-off on the engine to the top of the regulator. Bleed air departs the

regulator and flows to the jet pump assembly located within the air duct on the left side of the

engine compartment. The jet pump mixes bleed air with outside air. In the FRESH AIR

INCREASE range, outside air only flows through the jet pump. In the TEMPERATURE

INCREASE range, outside air mixes with bleed air which enters the jet pump through the sonic

nozzle. Outside air enters the jet pump through the butterfly (outside fresh air) valve. The

butterfly valve gives control of outside air only when the cockpit environmental control lever is

in the TEMPERATURE INCREASE range. A firewall gate valve located on the left side of the

firewall controls air flow from the jet pump and initially opens when the cockpit environmental

control lever is moved forward out of the OFF position.

Figure 20-2 System Components

COCKPIT HEATING, VENTILATING, AND WINDSHIELD DEFOGGING SYSTEM 20-3