What G force opens the anti-G valve during maneuvers?

The anti-G valve is designed to help combat the effects of G forces experienced during flight maneuvers, particularly when the aircraft is subjected to increased positive G forces. When the pilot experiences these increasing positive G forces, the anti-G valve opens to allow the appropriate amount of compressed air from the aircraft's system into the anti-G suit. This suit then helps maintain venous return and prevent the pilot from experiencing G-induced loss of consciousness (GLOC) by promoting blood circulation back towards the upper body and brain.

In this context, increasing positive G forces are critical because they place a strain on the cardiovascular system, making it harder for blood to circulate effectively against the direction of gravity. The functioning of the anti-G valve is thus directly linked to these elevated forces, and it provides essential support during high-performance maneuvering.