Most anti-g systems are similar to the one illustrated in figure 1-2. This system consists of a supply line, an air filter, a pressure regulating valve, a connecting hose, and a suit attachment fitting (single quick disconnect or composite quick disconnect). The air pressure used in this system may be taken directly from the engine compressor bleed-air ducting, but is usually taken off the air-conditioning ducting downstream from the heat exchanger.

Pressure Regulating (Anti-G) Valves 

There are two types of anti-g valves used on the various naval aircraft. One type has a dual pressure range (HI or LO) that maybe controlled by the pilot. The other type has a fixed pressure output that corresponds roughly to the high (HI) pressure output of the dual pressure valve. Both valves perform the dual functions of regulating the air pressure received from the aircraft's bleed-air system and metering this pressure in varying amounts proportional to the g forces exerted upon the aircraft and its occupants.

Newer aircraft are designed with an anti-g system that has a single-stage pressure regulating valve (fig. 1-3). This valve begins to open at approximately 1.5 g's, and pressure is supplied to the suit at the rate of 1.5 psi for each additional g. The valve is designed to receive air pressure from the bleed-air system at varying pressures and to meter a maximum of 10 psi to the anti-g suit. A relief valve bleeds off the excess air pressure

Figure 1-3.- Anti-g pressure regulating valve (single stage)

Figure 1-2.- Anti-g system.

and maintains a maximum of 9 to 11 psi in the valve outlet chamber. Figure 1-4 illustrates the operation of the single-stage anti-g valve. When a force of approximately 1.5 g's is exerted on the aircraft, the activating weight over-comes the upper spring tension and closes the exhaust valve (fig. 1-4, view A). As the weight travels downward, it further depresses the valve assembly, forcing the demand valve from its seat, thus overriding the pressure of the lower spring and opening the demand valve. Air pressure then flows past the open demand valve, through the

valve outlet into the valve outlet line, through the suit quick disconnect, and into the anti-g suit. As the g forces being applied to the aircraft are stabilized and become constant, the pressure under the activating weight diaphragm builds up sufficiently to lift the weight and to reduce the pressure on the valve assembly enough to close the demand valve (fig. 1-4, view B). The demand valve closes under pressure of the heavier lower spring, while the exhaust valve remains closed by the activating weight. The suit pressure is then trapped in the pressure outlet chamber of the

Figure 1-4.- Anti-g valve operation (single stage).

anti-g valve and remains constant until the g forces change. As the g forces decrease, the downward force on the activating weight diminishes to a point at which the upper spring lifts the weight off the exhaust valve. The pressure in the suit is then vented through the exhaust port (fig. 1-4, view C) into the cockpit.