10.24 Gravitational Forces

The human body is most accustomed to the gravitational force experienced on Earth, which is approximately 1G.

This is the force that we experience as normal gravity.

During flight, particularly during manoeuvring, the body may experience forces greater or less than 1G.

These forces may be:

• positive G, where blood tends to move towards the feet; or
• negative G, where blood tends to move towards the head.

Changes in G force affect the movement of blood within the body and can therefore affect:

• the circulatory system;
• vision; and
• consciousness.

10.24.2 Explain the effects of positive and negative accelerations on:

(a) the circulatory system

Acceleration affects the movement of blood within the body.

During positive G, blood tends to be forced towards the feet and away from the head.

This can:

• reduce blood flow to the brain;
• reduce blood pressure in the head;
• increase blood pooling in the lower body; and
• reduce the supply of oxygen to the brain and eyes.

During negative G, blood tends to be forced towards the head.

This can: