High Pressure Relief Valve

CHAPTER TWENTY TWO

T-34C AIRCRAFT SYSTEMS FAMILIARIZATION

WORKBOOK

The supply control lever is green and turns the regulator on and off. When aft in the OFF

position, no oxygen enters the regulator; when forward in the ON position, low pressure (70 PSI)

oxygen enters the cockpit regulator. The supply control lever should be "shear-wired" to the ON

position (See Figure 2). The diluter control lever is white and labeled 100% OXYGEN and

NORMAL OXYGEN. It selects 100% or diluted oxygen for delivery to the mask. When

forward in the 100% OXYGEN position, the mask receives undiluted and unpressurized oxygen;

when aft in the NORMAL OXYGEN position, the mask receives diluted and unpressurized

oxygen. The emergency pressure control lever is red and labeled EMERGENCY, NORMAL,

and TEST MASK. When forward in the EMERGENCY position, 100% oxygen is delivered to

the mask under a safe positive pressure irrespective of the diluter control lever. In the aft TEST

MASK position which must be held, 100% oxygen under positive pressure is delivered to the

mask. In the center NORMAL position, the mask receives oxygen with a composition as

selected by the diluter control lever.

A pressure gauge is located in the forward right corner of each control panel. Labeled OXYGEN

CYLINDER PRESSURE, it indicates supply cylinder pressure. The scale reads 0 - 2,000 PSI in

100 PSI increments. Acceptable pressure for flight is 1000 - 1850 PSI.

A blinker type flow indicator is located in the forward left corner of the panel. It indicates

oxygen is being released from the cockpit regulator to the mask. The blinker-vane will show

either black or white: black when no oxygen is released and white when oxygen is released.

Safety Precautions

Aviators' breathing oxygen is 99.45% pure oxygen. Pure oxygen under pressure will ignite

grease or oil spontaneously. Facial skin burn may result if oxygen and petroleum-based facial

products come in contact. Also, do not smoke while oxygen is in use.

High Pressure Relief Valve

A high pressure relief valve is located at the cylinder outlet to protect the supply cylinder against

damage caused by excessive pressure. At excessive pressure the relief valve opens and a plastic

blowout disc located above the flap on the right side of the aircraft is blown out and all oxygen in

the cylinder is dumped overboard. Absence of the disc provides a visual indication that the

cylinder is empty.

Regulator Contamination

To prevent cockpit regulator contamination, the diluter control lever must be placed in the 100%

OXYGEN position when the regulator is not in use.

22-4 T-34C OXYGEN SYSTEM