AGSM or G-LOC—Is the Squeeze Worth the Juice?

  • Published
  • By Maj Thomas "Vito" Massa
  • 12 ADS/SGGT
"Check away" and "Fight's on" are the calls; both aircraft then engage each other in a two-circle fight. Nine Gs slam against the pilots' bodies as they attempt to maneuver into an offensive kill position. Both pilots know the time-tested aircraft can survive the twists, turns and rigors placed upon them during flight, but without warning, one aircraft enters an extremely nose-low attitude and accelerates toward the terrain. "Knock it off ... pull up ... pull up ... recover and eject ... eject" are the radio calls. The aircraft impacts the ground, but you see a parachute, and immediately start the search and rescue. The above hypothetical scenario, as you may have guessed by now, was the result of gravitational-induced loss of consciousness, otherwise known as G-LOC.

Unfortunately, the threat and consequences of G-LOC are not new. In 1919, Dr. Henry Head described the problem of G-LOC, but used the phrase "fainting in the air" to explain the phenomenon. During World War II, G-LOC became better recognized within the aviation community, and the invention of the G-suit emerged, which is the same design used today. G-suits work by transferring a force via air-inflated bladders to the lower limbs to increase peripheral vascular resistance, thereby reducing venous pooling. This improves venous blood flow back to the heart and increases cardiac output. In pilot speak: a G-suit squeezes the abs and legs, forcing the blood up toward your cranium to help maintain vision and consciousness. It wasn't until the 1970s and the introduction of modern fighters, such as the F-15 and F-16, that G-LOC became increasingly recognized as a possible cause of a number of fatal aircraft mishaps. The United States, Britain and Germany began extensive research with the Human Centrifuge to investigate G-LOC. Pilot unconsciousness at the time was viewed as a barrier, and the purpose of the research was to come up with new methods/equipment to push the performance barrier back -- to make the human system less susceptible to the high G-environment. Modern G-suits, anti-G straining maneuvers, tilting seats, and positive-pressure breathing systems (Combat Edge) are the results of this approach. Each one has increased pilots' G-tolerance in measurable amounts and allowed us to operate better in the high G-environment; but together, they have not eliminated the pilot's susceptibility to G-LOC.

Still, we're faced with the challenges of G-LOC. Today's technologically advanced aircraft, such as the F-22 and F-35, are capable of operating in high G-extremes that can easily exceed the physiological capabilities of the operator. Existing equipment like the CSU-13B/P anti-G-suit being used in our legacy fighters are limited in providing the G-protection necessary to meet future mission demands. The physiological and equipment barriers of the past are still valid performance concerns today. It is unlikely that we can change man's physiological limitations to high-G, but we can provide better G-protection in the form of full-coverage G-protection suits.

Centrifuge comparative performance analysis has been performed on a variety of commercially available off-the-shelf anti-G suits. Testing has shown that by extending the surface area coverage of lower anti-G suits (full/extended coverage), coupled with positive pressure breathing for G, we can significantly improve G-protection capability and reduce aircrew fatigue. Improving the equipment we provide our warfighters with the latest full-coverage G-suit/systems to combat the effects of G-LOC is a good start. Although as a physiologist who has investigated too many "smokin' holes" and teaches methods to prevent G-LOC, it's important to emphasize that you mustn't rely solely on your equipment to mitigate the risk of G-LOC.

The majority of Class A and E physiological G-incidents result from an inadequate AGSM, due to task misprioritization. As operators of bone-crushing machines, you need to bring your "A" game every time to optimize performance when in the high G-environment. You're probably wondering, "What exactly does that mean to me?"

1. Daily Preparations -- Ensure you and your students, wingmen and flight leads are mentally and physically prepared for the demanding sortie. A good night's sleep, proper hydration, nutrition and a weekly fitness regimen are the assumed starting points.

2. Before Flight -- Assess your fitness to fly, and review your students' grade book and your personal performance on the last sortie. How long has it been since you or your wingman has flown (long layoff from high-G activity)? Are there any historical G-trends from members of the flight that need to be addressed? Does your squadron have a good G-ORM program in place? Did you thoroughly brief the high-G threat phases of flight and mental preparation required for an AGSM during tactical maneuvering?

3. During Flight -- Ensure the G-Awareness exercise validates your ability to survive in the high-G arena. All aircraft and G-protection equipment must be working properly. This is your opportunity to determine if you're feeling like that 9G warrior or if you need to employ old-man BFM tactics today. Adequately assess the onset of high Gs, which is easier said than done. It requires good AGSM habit patterns, muscle memory and G-situational awareness. Starting your AGSM after G-onset or waiting for light loss could be detrimental to your well-being. Unload the aircraft and start over, if necessary. Continually assess your G-performance and that of the other flight members between and during engagements. You may need to terminate early, especially if all the desired learning objectives have been met. (Say what? I still have a few hundred pounds of fuel; just one more set-up!) Most G-related incidents occur late in the sortie as the aircraft performs better, but human performance diminishes over time, due to fatigue. Call "knock it off" or terminate, and get that instrument approach if it's not your G-day. Don't worry about the repercussions -- tomorrow will be a better day!

4. Debrief -- Review AGSM performance throughout the sortie, using the tape review and assess proper equipment function. Annotate any G-trends (breath holding, exchange rate fast or slow, etc.) and reinforce the importance of establishing a subconscious AGSM habit pattern. If necessary, call upon your local aerospace physiologist to assist with 1 v 1 AGSM training. Call me if you don't have one!

BACK TO AGSM BASICS: (Review AFPAM 11-419, G-Awareness for Aircrew)

        - Anticipate the rapid G-onset
        - Preparatory breath inhalation with aircraft lift vector movement
        - Simultaneously tense all lower-body muscle groups, legs, butt, abs, (maintain this strain)
        - First exhalation on top of G or three seconds, followed by short/quick inhalation of less than one second
        - Minimize communications
        - G-strain continued until G is unloaded

Working in high-G environments is part of our daily operations. We must do whatever we can to improve safety, to lower the physiological risks that high-performance aircraft generate. Several variables factor into managing the threat of G-LOC. Once you hear "Fight's On," the standard of "Kill and Survive" requires you to be lethal at the merge, but more importantly, AWAKE! If you feel the squeeze of the G-suit, you'd better be prepared for the juice, the G-onset. We must continue to make leadership decisions and lifestyle choices to ensure we can fly, fight and win our nation's wars. You are our most vital asset and the most critical link in the chain to stop preventable mishaps before they occur.