Gravitational Forces

Question 1

What are the effect of positive and negative accelerations on the circulatory system?

Answer 1

• Positive G - the blood pressure in the head may fall to a point where blood supply to the eye and brain ceases
• Negative G - blood id forced upwards and can cause much greater discomfort than positive G, upward movement of blood can overload the heart, causing it to slow down.

Question 2

What are the effect of positive and negative accelerations on vision.

Answer 2

• Positive G = potential grey out, followed by tunnel vision, followed by blackout at prolonged acceleration above +5G.
• Negative G = blood is forced to the head and eyelids, red-out can occur.

Question 3

What are the effect of positive and negative accelerations on consciousness?

Answer 3

• Positive G = above prolonged exposure to +5 to +6G, may become unconscious. Due to blood being drained away form the brain and therefore also oxygen from the brain causing a type of hypoxia.
• Negative G = does not generally cause a loss of consciousness, however if heart rate is slowed down too far, could lead to hear stopping.

Question 4

What are the causes and symptoms of G-LOC (gravity induced loss of consciousness)?

Answer 4

• Prolonged exposure to +5 to 6G

Pilot will lose consciousness until the amount of g-forced is reduced. Recovery is delayed by the fact that the blood has concentrated in the lower limb where it does not readily return for re-circulation.

• Pilot of aircraft required to carry out high G manoeuvres wear special G suits which resist the pooling of blood.