Military Aviation Physiology

Military Aviation Physiology links: USAF School of Aerospace Medicine About Aerospace Physiology References and WWW Links Thanks to: William J. Tarver, Maj, USAF, MC, SFS Associate Director, Preventive Medicine / Aerospace Medicine Program Webmaster for the School of Aerospace Medicine, Department of Aerospace Medicine high-G CD-ROM HIGH G - PHYSICAL EXERCISE GUIDE FOR AIR FORCE AIRCREW. CD-ROM- MULTIMEDIA (Finnish, Swedish and English). Finnish Air Force, Tikkakoski 1998. Modern fighters present great demands on the physiology of the pilot. high-G gives basic information about the physiological effects of the G-forces and the means how to counter them. There is a large image bank for personal exercises. THE EDITORIAL GROUP OF THE CD-ROM-VERSION Pekka Kanninen, Col. (FAF ret), the commander of Lapland Air Command in Finnish Air force 1987-1994. Harri Rintala, M.Sc., researcher. Has been working as a physical training officer and researcher in the Finnish Air Force Headquarters. Pentti Kuronen, MD, Col., The Chief Flight Surgeon of the Finnish Air Force. Juhani Hipeli, Lt. Col., the chief of flight safety in the Finnish Air Force. Multimedia production: Tietovalta Oy Physical exercises: Physiotools ARM PAIN FAMONG SWEDISH FIGHTER PILOTS DURING HIGH + Gz FLIGHT AND CENTRIFUGE EXPOSURES Linde L and Balldin U Aviation, Space and Environmental Medicine + Gz induced arm pain occurs in connection with high +Gz loads in flight as well as in centrifuge tests of high performance fighter pilots. A questionnaire was sent to 35 Swedish Air Force Viggen and Gripen pilots who had previously participated in centrifuge tests at Brooks Air Force Base, TX between 1990 and 1995. 55 % of subjects reported that they had experienced arm pain during fighter flight at least once and 42 % more than 3 times. However, in centrifuge tests ratios were 82 % and 42 %, respectively. Arm pain was more common in in the centrifuge tests than in fighter flights and presence of arm pain during high + Gz flights is a phenomenon that should be taken into consideration when designing + Gz protective equipment. (Article sent by Tuomo Leino M.D.) ASEM V69N2: Improved anti-G protection boosts sortie generation ability. NASA Aviation Human Factors: Publications   COMBAT EDGE, is a useful adjunct in improving one's G tolerance, when used in conjunction with a G-suit covering the lower extremities and a properly performed Anti-G Straining Maneuver (AGSM). The positive pressure leads to an increased intrathoracic pressure, thus increasing cardiac output during G, much the same as the AGSM. Thus less effort is expended on performing the AGSM, aircrew are less fatigued, and thus able to sustain prolonged or recurrent exposures to high G for longer periods. The pressure is continuous as long as the aircraft is under G, and is scheduled along a linear gradient starting at 4 G, and increases to a pressure of 60 mmHg at 9 G. Obviously, exhalation and communication require some effort. COMBAT EDGE should not be used without a G-suit as the increased intrathoracic pressure would present an even greater pressure gradient to overcome, for the blood returning to the heart from the lower limbs. Eventually venous pooling and decreased cardiac filling and output would eventually occur. The two systems work will together and some studies show a slight synergistic effect when used in combination. Of note, the counterpressure jerkin vest used in COMBAT EDGE was included as safety measure to prevent possible overinflation injuries to the lungs. The RAF did some work in this area and showed that the external counterpressure vest provided no additional protection, as the increased weight of the chest wall structures under high G provided sufficient additional splinting. Interesting from the standpoint that most aircrews using COMBAT EDGE voice objections about how hot the vest is. Mark Mavity, Maj, USAF, MC, SFS Resident, Aerospace Medicine USAFSAM, Brooks AFB <<< >>> Aeromedical Mailing List. To respond to the list send your reply to : aeromed-list@silverquick.com To leave the list send e-mail to : Listmanager@silverquick.com with message body to read: leave aeromed-list http://www.ozemail.com.au/~dxw/aeromed-list.html This article is posted via Tuomo Leino   IMPROVED ANTI-G PROTECTION BOOSTS SORTIE GENERATION ABILITY Andrew Tong, MD, Ulf Balldin, MD, Ronald Hill, PhD and James Dooley, PhD Armstrong Laboratory, Brooks AB, USA and National Defence Research Establishment, Sweden Aviation Space Environ Med 1998;69:117-120. Armstrong Laboratory of USAF tested their standard CSU-13B/P anti-G ensemble (STD) and new COMBAT EDGE/ATAGS (GE/ATAGS) anti-G ensemble with positive pressure breathing system in centrifuge at Brooks AFB, TX, USA. 12 male and 3 female pilots performed 3 centrifuge-based simulated air combat sorties with both anti-G ensembles. Each sortie consisted of four different G-profiles: 1) gradual onset profile up to + 9 Gz 2) + 4.5 to +7.0 Gz simulated air combat maneuver (SACN) 3) + 5.0 Gz to + 9.0 Gz tactical air combat maneuver (TACM) and 4) + 5.0 to + 9.0 SACM. There were no incidents of G-LOC (G-induced loss of consciousness) with CE/ATAGS anti-G protection with positive pressure breathing system. However, standard anti-G protection of USAF (STD) resulted 4 G-LOCs in the centrifuge. Also performance with STD was significantly lower than with CE/ATAGS, and pilots reported faster recovery times after centrifuge test with CE/ATAGS. The researchers of USAF concluded that modern positive pressure breathing technology with full-cover G-suit (used in Finnish Hornets) provides superior G-protection when compared to standard USAF anti-G suit. The markedly shortened recovery time between sorties with CE/ATAGS suggests increased operational availability of fighter aircrew, thus improving sortie generation. Modified by Tuomo K. Leino, MD

The new F-18 Hornet flight gear:

A Gentex (US) helmet with pressure breathing and twin visor (clear & dark), NVG attachment to be designed ML Lifeguard (UK) flight suit underneath. Two different types of woolen underwear and a fleece jacket. Winter jacket to be selected in the near future On-board Oxygen Generation System (OBOGS) Pressure regulator to adjust the pressure in the oxygen mask Pressure vest (ML Lifeguard) to give positive pressure to upper body under G-loads. Pressure breathing and vest add about 1,5 G tolerance compared to the traditional G-suit Full cover G-suit (ML Lifeguard) with large air bladders. Fast reacting G-valve in the aircraft. Adds one more G compared to the traditional G-suit Four leg restraints to attach to the Martin Baker SJU-17 NACES ejection seat Immersion suit for over water flights

Dr. Mavity: Anti-G-straining-maneuver The current USAF approved Anti-G Straining Maneuver (AGSM) is the L-1. It combines a regular, 3 second strain (valsalva) against a closed glottis, interrupted with a rapid exhalation and inhalation (< 0.5 seconds), with tensing of all major muscle groups of the abdomen, arms, and legs. Properly done, it buys a pilot about an additional 1.5 G's, the same as the current standard anti-G suit, thereby giving an average 3 G protection above resting G tolerance levels (around 6 G's for most aircrew). The old M-1 was essentially the same, but against a partially open glottis, causing the pilot to audibly grunt during the strain (lower intrathoracic pressures achieved so no longer recommended). The US Navy teaches a slight variation of the L-1 called the Hook Maneuver in which the pilots initiate the strain phase by saying "hook" as they begin to strain. This helps ensure a completely closed glottis. Otherwise, no significant differences from the USAF L-1 that I'm aware of. The Chinese teach a Qigong Maneuver that I admit I still don't fully understand despite reading the articles. Postive pressure breathing systems such as the USAF COMBAT EDGE offer no addition protection to higher levels of attainable G, but do significantly decrease the level of straining effort required for a given level of G, thereby reducing workload and fatigue, and hence improving sustained G tolerance to repeated G exposure. Numerous sources abound on the topic. A literature review will reveal an abundance of published articles in the Aviation, Space, and Environmental Medicine journal. The current 'bibles' of aerospace medicine, DeHart's Fundamentals of Aerospace Medicine and Ernsting's Aviation Medicine also offer good discussions on the topics. In putting together briefings for aircrew on GLOC avoidance, you must also include adequated discussion of an appropriate conditioning progam which combines 20-30 minutes, 3-4 times per week of both weight training (both of upper and lower body muscle groups [pilots frequently overwork upper body at the expense of lower body]) and aerobics. Wt training increases muscle mass and provides a more powerful strain and hence increased venous return from the extremities. Aerobics increase aerobic capacity and thus G endurance in cases of prolonged/repeated G exposure. One myth worthy of dispeling is that excessive aerobic conditioning will decrease G tolerance. In extremely, aerobically well-conditioned athletes (distance runners and triathletes), all that has ever been demonstrated is a decrease in resting G tolerance. However, with an adequate AGSM, no decreases in total G tolerance were seen. In reality, the needed for such excessive training offers little additional benefit to pilots (law of diminishing returns) and their limited time is better spent balancing their aerobic conditioning program with some wt training. Mark Mavity, Maj, USAF, MC, SFS Resident, Aerospace Medicine USAF School of Aerospace Medicine Aeromedical Mailing List: To respond to the list send your reply to : aeromed-list@silverquick.com To leave the list send e-mail to : Listmanager@silverquick.com with message body to read: leave aeromed-list http://www.ozemail.com.au/~dxw/aeromed-list.html   Simo Siitonen, M.D. + Gz-forces in F-18 Hornet In operational use F-18 Hornet has G-onset rate up to + 9 Gz. Contrary to previous high-performance aircraft of Finnish Air Force (FAF) Hornet can also maintain that Gz level for some time. This will result to physiological problems in form of circulation disturbance. Blood will be packed in lower body and eye-level blood pressure drops dramatically. After 5 seconds grey out occurs and if Gz load remains black out will appear shortly after grey out. A pilot loses his/her consciousness if Gz load is not rapidly decreased. Gz-force induced loss of consciousness (G-LOC) is the deadliest enemy of a fighter pilot if we think military flying from the aerospace physiology aspect. Eye-level blood pressure drops 22 mmHg for every Gz. Normally eye-level blood pressure is about 100 mmHg, but during + 4 Gz exposure eye-level blood pressure has dropped to 12 mmHg, if a pilot is not using any G-protection. Without G-protection average pilot can handle + 4 Gz force without problems. During WW II G-suit was introduced to better pilots G-tolerance. Together with L1/M1 counter maneuvers (muscle contractions and intrathoracic pressure increasement) G-suit will increase G-tolerance to + 8 Gz for short time. After + 2 Gz in modern fighters G-suit pressure will increase 8.6-10 kPa for every G, but maximum pressure is 69 kPa. Full cover G-suit (ML Lifeguard) of Finnish F-18 Hornet has 45 % larger air bladders than previously used G-suits of FAF. This means that G-tolerance has increased from + 1.5 Gz (old G-suit) to + 3 Gz (full cover G-suit) because of G-suit. Pilots use G-suits because: 1) G-suit increases blood vessel resistance in lower body leading to increased blood pressure, 2) G-suit induced intra-abdominal pressure elevates heart 3 cm and shortens heart-brain distance and 3) venous blood is not situated in lower body and heart has enough venous blood in use to pump it to brain. Pentti Kuronen, M.D. (Chief Flight Surgeon of FAF) led an evaluation team which selected pressure breathing system (ML Lifeguard) for F-18 Hornet of FAF. Also pressure vest, regulator and on-board oxygen generation system (OBOGS) were included in this system. Increased intra-thoracic pressure made by pressure breathing system increases G-tolerance about + 2 Gz. This way also risk of G-LOC decreases significantly. Why fighter pilots and flight surgeons want to avoid G-LOC ? During G-LOC absolute incapacitation lasts 12 to 20 seconds but relative incapacitation can take more than 3 minutes. During those minutes anything can happen ! In US Air Force 12 % of the fighter pilots had experienced G-LOC. The same rate in US Navy was 14 %. Based on centrifuge experiences flight surgeons know that 50 % of G-LOC pilots do not remember their G-LOC experience. This means that one fourth of fighter pilots in USA have been on the edge at least once during their career. Modern technology together with understanding of aerospace physiology has give fighter pilots tools to fight not only against the enemy, but also against themselves in high Gz environment. Modified by Tuomo Leino, M.D.   David G. Newman, M.B., B.S. + Gz-induced Neck Injuries in Royal Australian Air Force Fighter Pilots. Aviation, Space and Environmental Medicine 1997;68:520-4 + Gz-induced neck injuries are a relatively common occurrence in pilots of high performance aircraft. 1988 Dr. Knudson reported that 74 % of surveyed F/A-18 pilots had experienced acute neck pain during high +Gz. 26.8 % of US Navy aviators had consulted their flight surgeon because of G-induced neck pain. In Finland, cumulative incidence of 37.9 % in BA Hawk Mk 51 pilots was found by Olavi Hamalainen, M.D., Ph.D. (Air Force Academy, FAF). He also found in his thesis that all neck injuries occurred when a pilot was checking his "six" (maximum rotation of the head) during over + 4 Gz stress. In this study 85 % of RAAF fighter pilots reported to have experienced acute neck pain during high G, particularly those flying F/A-18. 52 fighter pilots of RAAF Base Williamtown participated this study and average total flying hours of subjects was 2066 h (range 360-5600 h). The survey was done via anonymous questionnaire. 35 out of 41 Hornet pilots reported to experience acute G-induced neck pain during their career. Only 23 % of pilots reported doing any specific neck strengthening exercises. However, 63 % of pilots reported that they usually performed some form of preflight neck exercise. Only 27 % of pilots had sought medical attention because of their neck pain experience. This demonstrates that most of injuries were simple muscle sprains. However, nine pilots (17 %) were taken off flying duties as a result of their neck injury. Interestingly, six of them had not performed neck condition exercises. Based on the studies of G-induced neck pain, it seems reasonable to suggest for F/A-18 Hornet pilots that both regular long-term neck muscle training and preflight stretching are important in minimizing the rate of neck injury. If acute neck pain occurs, pilots should more often consult a flight surgeon because there is always a risk of serious neck trauma behind the neck pain. by Tuomo K. Leino, M.D.     David G. Newman, M.B., B.S. Head Positioning for High +Gz loads: An Analysis of the techniques Used by F/A-18 Pilots. Aviation, Space and Environmental medicine. 1997;68:732-5 42 F/A-18 Hornet pilots (RAAF, Williamtown) answered in anonymous questionnaires to the question: Have you developed a strategy during high +G to minimized risk of acute neck pain ? Of the 42 respondents, 29 reported that they did have a particular strategy for use of high +Gz. Several pilots reported using many different techniques, accounting for the total of 66 responses. Most common strategy (20 %) was to set head position before application of high G. 15 % of Hornet pilots brace head against ejection seat structure before high G. 14 % moved their head in only one plane at a time. 11 % used shoulders to aid rotation of head. Also 11 % kept head aligned with body under G. Only 6 % reported that they restrict movement under high G and move head only under low G. 6 % moved their upper body as well as head during high G. Interestingly, 17 % of F/A-18 Hornet pilots answered that they did not use any strategy for head positioning, as they were generally able to move their heads around with apparent impunity under whatever +Gz loads the tactical situation called for, and were not afraid of neck injury. The results of this study showed that most F/A-18 Hornet pilots have developed individual strategies of head positioning under high +Gz in order to protect their cervical spines from G-induced injury. Tuomo K. Leino, M.D. Aerospace Medicine Problems of Saab 35 Draken Super-Stall Due to unique aerodynamical characteristics of Saab 35 Draken interceptor, special psychological and physiological problems are involved with Draken super-stall. The most important concerns are situation awareness (SA), +Gz stress and push-pull effect, possibility of neck injuries and spatial disorientation. Situation Awareness (SA) A fighter pilot have to cope with rapidly changing situations during different flight phases. SA is aerospace psychological term that try to model the pathway from state of the environment to decision making and performance of actions in cockpit. The most important origin of sensorial information in pilots are eyes. Visual information must first be transited to brains and then perception of elements in current flight situation must be understood. After that comprehension of current flight situation can be made by a pilot. Then a pilot have to understand how the flight situation will be changed in the future. Through this process decisions can be made in one-channel pathway (e.g. one decision each time) and this information will be transited to muscles via motoneurons in order to make thrust of stick actions. There are many factors that are involved with SA. System capability, interface design, stress, physical and psychological workload, complexity of flight situation, automation of aircraft, individual information processing mechanisms, memory, personal abilities, experience and training will affect how a pilot is making decisions and actions via SA. Draken super-stall is a rare but very dangerous flight situation typical to Saab 35 Draken interceptor. It is extremely important for a Draken pilot to quickly understand that this flight situation is super-stall. Actions of Draken super-stall can NOT be overlearned and hence SA is one of the key factors in order to make correct stick actions during Draken super-stall. Of course, different models of stick actions are taught to Draken pilots depending on inner or outer super-stall. It is important that pilot is all the time prepared mentally for Draken super-stall possibility. Also coolness under super-stall is very important. Correct stick actions are based on SA and will decrease physical workload of Draken super-stall. +Gz stress and push-pull effect Depending on air speed the +/- Gz load can vary from 7-12 G. Also the G-onset is very rapid, 7-10 +Gz/s. Brain has a oxygen reserve for 5 sec but after that +Gz induced lost of consciousness (G-LOC) will follow. However, in Draken super-stall G-load normally decreases rapidly after early state rapid G-onset. On the other hand, stable and swinging Draken super-stall vary a lot when G stress is concerned. In stable super-stall G-loads are minimal after rapid G-onset at the beginning of Draken super-stall, but in swinging super-stall push-pull effect play an important role. After negative Gz swing phase positive swing phase will follow. Based on aerospace physiological studies we know that G-tolerance dramatically decreases after -Gz phase (gray out limit is 2-3 G lower than normally). This way also the risk of G-LOC increases. The G-LOC is one of the most dangerous risks during swinging super-stall, especially if pilot is not doing right stick actions during Draken super-stall. If a pilot pushes himself to G-LOC, normal flight capability is achieved after 1 to 3 minutes ! This is why L1/M1 countermaneuvers should be made also during swinging Draken super-stall. Possibility of neck injuries Rapid G-onset at early phase of Draken super-stall can also be very dangerous for the neck. Based on Dr. Hamalainen`s research we know that over +4 Gz load and twisted head position are the key factors behind the flight induced neck injuries. This is why pilots should remember to concentrate on head position if that is possible. The following comments concerning neck problems are from F-18 Hornet pilots of RAAF: - "Most neck pain manifests itself after flight" - "Specific training in neck exercises would be benefit" - "Neck warm-ups prior flight help a lot" - "I am concern about my quality of health in the later years" (a pilot who is about to retire) Spatial disorientation As mentioned before, most of the information of flight situation is oriented from the vision. The other information is based from inner ear and pressure receptor of joints and ass. The weather (VMC/IMC) affects a lot how quickly a pilot can observe rapid changes in flight situation. In order to maintain spatial orientation in IMC conditions a pilot have to focus immediately on his flight instruments and keep his concentration on these instrument during Draken super-stall. This is the only way to survive from Draken super-stall in IMC conditions. Do not fly with your ass ! Although Draken super-stall is a rare flight situation, Draken pilots should be mentally prepared and trained in order to face the super-stall. Also aerospace medical problems of Draken super-stall should be remembered in order to increase flight safety of Saab 35 Draken. Tuomo K. Leino, M.D. Neuroendocrine Unit Department of Physiology University of Oulu   Female Military Pilots in Finnish Air Force Tuomo Leino, M.D. Many air forces globally have female pilots flying helicopters, liaison aircraft, some even high-performance interceptor. E.g. Norwegian Air Force has one female F-16 Falcon pilot with over 600 falcon flight hours. However, US Air Force and US Navy did not use female pilots in Combat Flight Missions until November 1993. Especially US Navy has done a lot research work in order to evaluate female fighter pilot`s ability to perform in combat situations with high-performance interceptors. First two female student pilots started their training in Air Force Academy of Finnish Air Force August 1997. Recently Carreta (psychologist, Amstrom laboratory, US Air Force) reported that despite male-female mean scores of US Air Force Pilot Selection test differ, confirmatory analyses indicated that the same factors were measured in psychological evaluation. However, male and female cadets performed equally well in Cadet School and their flying skills showed similar structure. Conclusion is that from aviation psychological point of view female and male pilots are in the same line. The military aviation physiological point of view is not so clear. There are no good studies on this subject. We know that US Navy has a lot of problems with female pilot`s + Gz tolerance. Three years ago 50 % of US Navy T-38 student pilots could not found G-suit that would fit. Female anatomy especially in pelvis area is very different to male anatomy and all G-suits are designed for male pilots ! This year US Navy introduced a new female shape G-suit, but still 20 % of female pilots has problems with unfit G-suit. Of course unfit G-suit will drop G-tolerance up to 2.5 G. Dr. Chelette from Amstrong Laboratory, Us Air Force, did a study with nine female fighter pilots in the Dynamic Environment Simulator (DES). DES is normal fighter simulator situated in centrifuge and these female subjects performed a complex combat flight mission in high + Gz environment (max +9 Gz). Results showed that G-tolerance with fit G-suits is the same compared to male fighter pilots. However, female flight performance was 15% lower than male fighter pilot performance in equal conditions. Conclusion is that female fighter pilots have to push much harder in high G environment and this effort will decrease their ability to make correct tactical maneuvers in order to get clear gun or missile shot. Based on discussions with Dr. Hamalainen, M.D., Ph.D. (Air Force Academy of FAF), possibility of G-induced neck injuries in female pilots is predicted to higher compared to male pilots. No studies are done on this issue, but in car accidents incidence of whisp splash neck injuries is 20 % higher in females based on anatomical structure of female neck. In near future Finnish Air Force will make decision about female pilots in active duty in FAF. There are examples even in Scandinavia that female pilot can fly high-performance aircraft. On the other hand, most female pilots in other air forces are situated in liaison or helicopter squadrons. Finnish Air Force policy is to train only interceptor pilots, when applicants are selected for cadet school. From my point of view, FAF should consider the decision very carefully in order not to get disappointments and money waste during interceptor pilot training. by Tuomo Leino, M.D. Oulun yliopiston fysiologian laitos/MATINE homepage: http://cc.oulu.fi/~tleino (with links to aerospace medicine)   Aerospace Medicine Links: Aviation Medicine & Aerospace Medicine Home Page Night Takeoffs AVMED:The Leans

Home Latest Topic | Air Warfare | Air Shows/Conferences | Fighter Tactics | Fighter Aircraft | Missiles | Fighter Aviation Topic | Fighter History | Warbirds | Magazines | Current News | Links | Physiology | Photo Gallery | Bibliography | SIIVET - Wings | What's New J Lindberg. Copyright © 1997-2006 Fighter Tactics Academy. All rights reserved. Revised: tammikuu 03, 2006.