Fighting G-LOC (how not to sleep while flying)

Emergency Maneuver Training will expose the pilot to forces and accelerations that he/she is unlikely to have experienced in previous flight activities.  Increased G forces are a serious matter that demand a heightened level of awareness as to the risks.  Subjecting oneself to increased positive G force does not necessarily mean that you will simply go unconscious as this is the final stage of exposure.  The risk from high G's is not limited to large increases (+3 or more) either,  low increases in G force over a long period of time can be just as dangerous. 

There are several levels of exposure to increased G leading to unconsciousness:

Gray-out: The onset of increased G forces will begin the migration of blood from the head.  The vision is the first thing to go.  Tunnel vision occurs at this stage with the tunnel rapidly getting smaller.

Black-out: All vision is gone but you are still conscious and aware except for the total lack of sight.

G-LOC:  G induced Loss Of Consciousness.  You are sleeping and your body goes limp.  The good news is that whatever force you were applying to the flight controls has ceased.  Within a few seconds you will wake up in a confused state as the G load returns to normal and your heart pumps blood back up into your brain.  You may have dreamed that you were flying and woke up to discover that you really are!  It can take several minutes to completely regain your facilities.

The military has been studying this for years and developed techniques to maintain control of your body during high G flight.  The most effective technique is the "HooK" maneuver.  In the following article, Matthew Soltis describes his experience with high G flight and the application of the Hook maneuver:


                      Power Breathing, the Jet Jock Style

                                                               Matthew G. Soltis

With over 1500+ hours in the backseat of an F/A-18D Hornet, I became quite adept at power breathing and intra-abdominal pressure (IAP). Of course, my purpose then was to keep blood in my head and not my feet while under the influence of greater than 7 g’s. What I’ve found recently, since discovering Pavel’s techniques, is the same techniques we used in the cockpit can be applied in the gym.

G-LOC (Loss Of Consciousness due to excess acceleration)
With the advent of highly maneuverable jet aircraft came the necessity to protect the crew from passing out under very high acceleration (g’s). The average, fit aviator has about a 3g “naked” limit, which comes from automatic tightening of blood vessels forcing blood to the brain. G-suits (inflatable chaps) add another 1.5 to 2.0 g’s, giving the crew a 5g capability without any additional techniques. So how does one withstand at 30+ second, 7.5 to 9.0 g turn in the latest fighter aircraft? In the Vietnam era, they were taught the “M-1” maneuver, which, simply put, is simulating a bowel movement without actually dirtying your skivvies. Research progressed, thankfully, and since about 1990, the technique of choice is the “hook” maneuver.

The “Hook” Maneuver
This is a simple oral/breathing technique that was taught to me in one day, yet served me well throughout my career. Remember, the backseater does not initiate the high-g turns and, therefore, is at a disadvantage of not always being able to pre-strain. The “hook” maneuver always came through, however, and I could brag that I never lost consciousness – though there were times I wanted to smack the pilot with my kneeboard for the lack of warning. Anyways, here’s the technique in its simplistic entirety:

NOTE: Before we start, say the word “hook” and notice that that the “k” comes out like “hook-eh” or “hook-ah”. This is important.

  1. Take a belly full of air

  2. BEGIN to exhale while forcefully voicing the word “hook”

  3. HOLD the “k”. You shouldn’t have exhaled much at all to this point, and now should feel your throat close (glottis) and your abs tighten.

  4. You now have good IAP to conduct a rep or half-rep.

  5. You release the IAP by relaxing the throat while forcefully finishing the “eh” or “ah” part of the phonetic “hook”.

  6. If your rep is extremely long or you’re isometrically holding a position, you can RAPIDLY repeat steps 1-3, though the inhale will not be very deep.

Cautions, Disclaimers, and Whatnot
Remember that this technique was designed to force blood to the brain. It does. So, if you have medical concerns about popping blood vessels in your cranium, take it slow and consult your doc. For me, I only need about 50% of the IAP in the gym compared to what I used in the jet. However, I can only squat a small dog, so you big fellas may need a little more.

Final Comments on Astronomy
Uranus is something I personally don’t recommend “locking”, “puckering” or in any other way manipulating. The “M-1” maneuver of old relied on this and studies showed that under extended g’s, relaxations were involuntary – with hemorrhoids prevalent. So, unless you’re a black belt in sphincter control, just let the “hook” raise your IAP.


Matthew G. Soltis
Former Marine Corps Officer and Aviator
Present middle-aged scientist getting back in shape


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