What happens to blood pressure under excessive positive G force?

Under excessive positive G force, blood pressure can drop to insufficient levels due to the body's inability to maintain adequate blood circulation in the face of increased gravitational forces. When an aircraft experiences positive G forces, blood is pulled away from the brain and vital organs, which can lead to reduced blood flow, a condition known as "G-induced Loss Of Consciousness" (GLOC). As a result, the body may struggle to maintain sufficient blood pressure, causing symptoms like dizziness or even fainting if the G forces exceed the body's capacity to compensate.

In this context, the other options do not accurately describe the physiological response under excessive G forces. For example, while one might assume blood pressure would increase significantly (as seen in some scenarios), in this case, the gravitational forces can overwhelm the body's ability to regulate and maintain appropriate blood pressure, leading to a drop instead. Similarly, the notion that blood pressure remains steady or fluctuates greatly does not align with the typical physiological responses observed during high G environments, where the body is under significant stress and unable to maintain normal circulation effectively.