G-Included Loss of Conciousness

T-34C CONTACT

CHAPTER TEN

pilot. Most T-34C G-LOC episodes occur during rapid G-loading of 3 to 5 G's over 2 to 5

second intervals. Pilots can prepare themselves for the physical stress of rapid accelerations and

therefore prevent G-LOC by taking certain precautions:

Learn and utilize the proper Anti-G Straining Maneuver (AGSM), more commonly called

the "HOOK Maneuver." There are two components to the recommended AGSM:

The first component is a continuous and maximum contraction (if necessary) of all

skeletal muscles including the arms, legs, chest, and abdominal muscles. This tensing

of the skeletal muscles restricts blood flow in the G-dependent areas of the body and

thereby assists in the retention of blood in the thoracic region (including the heart)

and the brain.

The second component of the AGSM involves repeated closing of the respiratory

tract at 2.5 to 3.0-second intervals. Its purpose is to counter the downward G force by

expanding the lungs and increasing the chest pressure, thereby forcing blood to flow

from the heart to the brain.

The respiratory tract is an open breathing system which starts at the nose and mouth and ends

deep in the lungs. It can be completely closed off at several different points, the most effective

of which is the glottis. Closing the glottis (which is located behind the "Adam's Apple") yields

the highest increase of chest pressure. The glottis can be closed off by saying the word "HOOK"

and catching it about of the way through the word ("Hooo-"). This should be done after a deep

inspiration, followed by forcefully closing the glottis as you say "HOOK." Bear down for 2.5 to

3.0 seconds, then rapidly exhale by finishing the word HOOK ("-ka"). This is immediately

followed by the next deep inhalation, repeating the cycle until the G-loading is discontinued.

The exhalation and inhalation phase should last for no more than 0.5 to 1.0 second. Since the

blood pressure falls dramatically during this phase, its duration must be kept to a minimum.

WARNING

Do not hold your respiratory straining too long (more than five

seconds) since this will prevent the blood from returning to the heart

properly and may result in loss of consciousness.

Anticipate the onset of high G forces whenever possible. Skeletal muscles should be tensed prior

to the onset, coupled with the "HOOK" respiratory cycle as the G-loading increases. Initiating

the AGSM too early can inhibit the body's natural cardiovascular reflex responses, while

beginning too late creates a deficit situation which may be difficult to overcome.

NOTE

If properly performed, the AGSM should provide adequate protection

against G-LOC while performing the various aerobatic maneuvers. If

you experience difficulty, or are in doubt as to whether or not you are

executing the maneuver correctly, see your squadron flight surgeon or

wing Aeromedical Safety Officer.

INTRODUCTION TO AEROBATICS 10-5