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U.S. Military Aerospace Physiology

By In Aerospace Medicine, Blog, Guest Post, History, . . . On February 26, 2015

Aerospace Physiologists at work

Aerospace Physiologists at work

Aerospace and Operational Physiology (AOP) has the unique challenge of bridging physiologic sciences with the operational environment.  Many people think “they just work with pilots and do altitude chamber training.”  While we do frequently work with pilots and other aircrew, many are unaware of other human factor issues on which we are consulted by our warfighters.  Some of the topics that AOP’s serve as human factors experts about are fatigue, shiftwork analysis, cognitive workload, stress, man/machine design and interface, thermal stressors, mishap investigation and analysis, and space operations.  We are also commonly consulted on the traditional concepts of hypoxia, trapped/evolved gases, and nutrition, making this career field unique in its vast scope and breadth.  Our constant challenge is to aid in improving performance in all environments and conditions.  So, where did AOP’s come from?  How did this career field get its start?



Otto von Guericke  (1602 - 1686)

Otto von Guericke (1602 – 1686)

Many believe it all started with the Wright brothers in 1904 with the birth of aviation.  Actually, our roots trace back even farther to a man named Otto van Guerick (1602 – 1686).  He was a German scholar who invented the world’s first air pump in 1650, which provided significant contributions to our understanding of high altitude physiology.  Twenty years later, in 1671, Robert Hooke invented a vacuum pump and the world’s first altitude chamber.  Interestingly, Hooke was an assistant researcher for Robert Boyle (as in Boyle’s Law).  A discussion specifically on the various gas laws can be found here.  It would be two centuries after this time before the next significant contribution. From 1830-1886, Paul Bert completed his work on high altitude physiology and decompression sickness.  His work with the effect of hyperbaric and hypobaric environments would pay huge dividends in the upcoming WWII and was a starting point for understanding the effects of low pressure on astronauts.

Wright Flyer at Kitty Hawk (1903)

Wright Flyer at Kitty Hawk (1903)

Now enter the Wright brothers at Kitty Hawk in 1904.  What started at just 6.8 mph a few feet off the ground expanded to 126 mph and altitudes of 20,000 ft.  The military became quite interested in this new flying machine.  During WWI, when ground troops were left stuck and immovable in the trenches, the flying squadrons had mobility.  However, the mishap rate for the first year was atrocious.  Was it because they were shot down or had mechanical problems?  No.  Of the 100 aviators killed, 90 of them were found to be caused by “human error.”  This concept of human error has been essentially replaced by the term ‘human factors’; enter the dawn of aerospace medicine and aviation physiology.

The USAF School of Aerospace Medicine in WPAFB, OH

The USAF School of Aerospace Medicine in WPAFB, OH

In 1916, U.S. involvement in WWI led to the establishment of an air service in the military.  The U.S. War Department issued Special Order No. 243, which instructed Major Theodore Lyster, the first Chief Surgeon of the Army’s aviation section, to “…take whatever steps needed to establish the practice of aviation medicine” and created a lab at Hazlehurst Field outside Mineola, Long Island, NY in 1917.  This lab would soon be moved to Mitchell Field, Long Island in 1919.  After WWI ended, resources began to wane.  Teaching continued, but unfortunately the research mission dissolved.  In 1922, the lab officially became the School of Aviation Medicine (SAM) and was moved to San Antonio, TX, which was only logical to be closer to the pilot training facilities.  The altitude chamber, however, was left back in New York.

Through the 20’s and 30’s, the competition for speed, altitude, distance, and duration was underway.   By 1930, the B-17 bomber could reach altitudes of 30,000 ft. without bombs and travel at 230 mph on average.  With this increase in altitude, questions began to surface regarding the physiological hazards.  What happens during a decompression? What if the pilot has to bailout?  Since the SAM lab was dissolved, who could find the answers to these questions?  Who would investigate?

Boeing B-17 Flying Fortress


Maj General Malcolm Grow (1887 – 1960)

Maj General Malcolm Grow (1887 – 1960)

A young flight surgeon named Malcolm C. Grow at Wright Field identified this need.  In 1933, Maj. Grow was granted a lab and recruited Capt. Harry George Armstrong.  By 1935, they had established the Physiological Research Unit where they received a new low pressure chamber and found the one Lyster had left behind when SAM packed up to Texas.  They were in business and ready by 1937.  Their new facility also had a centrifuge.  Interestingly, this new lab sparked some healthy competition from those at SAM.  Weren’t they the ones who received Special Order 243 after all?  A little competition helped research to flourish.  Armstrong published over 30 papers and “Principles and Practice of Aviation Medicine,” which became the standard authority in aerospace medicine for decades.

WWII began, and in 1942, the Air Surgeon instituted the “Altitude Training Program.”  It was AF-wide and mandatory for aircrew members to complete.  During this expansion, doctors and scholars were assembled into 45 units to instruct on oxygen equipment and the physiological hazards of flying.  Other training topics included night vision training, G-forces, and thermal stress.  When the war ended, work dried up, and the doctors and scholars left to go back to private practice and teaching in the civilian sector.  After the Air Force became a separate military branch distinct from the Army in 1947, the Aerospace Physiology program was reactivated in 1949 by Col. Alonzo Towner, who was the surgeon for the 8th AF.  He expanded it into the Aerospace Physiology Training Branch where he initiated written tests, chamber technical orders, modified the chamber to allow rapid decompression, night vision trainers, and first training charts and slides.  He opened the first 13 chamber units in 1950.

Altitude Chamber Hypoxia Training

Altitude Chamber Hypoxia Training

Since the scholars and doctors returned to their civilian jobs, Col. Towner turned to pilots as the new instructors.  The program soared through the 1950s.  By 1956, there were 51 Physiological Training Units.  Oxygen consoles, pressure suits, and ejection seat trainers were also added to the training.  The 1960s brought even more advancement, and the program was reorganized under the Aerospace Medicine Division.  High altitude airdrop support (HAAMS) began in the early 1960s, which became prominent during the Vietnam Conflict.

So where are AOP’s today?  The question is, where aren’t we?  While the number of altitude chambers has decreased, Aerospace Physiology Training Teams have become more prolific and continue to expand in volume and breadth of mission.  Within these units, there is an AOP officer and, if lucky enough, an AOP (enlisted) Technician.  AOP Training Teams conduct aircrew training using a Reduced Oxygen Breathing Device (ROBD) paired with the Hypoxia Familiarization Trainer (HFT) to simulate the effects of altitude and hypoxia (see previous post on hypoxia) while keeping them on the ground instead of inside the altitude chamber.  This new approach to training aircrew who have been through the chamber previously joins the classic flight simulator environment with a reduced oxygen control system to allow AOP’s to tailor training in a safer (no chance for Decompression Sickness or Trapped Gas from hypobaric exposure – see previous posts for more info) but highly realistic modality.  The AOP team is also involved in human performance, providing expertise and consultation to all units across their base.  Projects can include analyzing shift work schedules for units like security forces, air traffic control or medical personnel; working with safety to look at mishap trends and investigating mishaps; or partnering with nutrition to provide education on supplement use. 

Given the countless number of human factors that exist, which effect both safety and human performance optimization, the sky  really is the limit as to what this career field has to offer.  The AOP career field continues to prove its value through innovation and technology, enhancing the warfighter capability.  Fly, Fight, Win!



  1. Brandt, Y. “High Points in Aerospace Physiology: A USAF Perspective, Part 1”. Aviation, Space, and Environmental Medicine (2010) May; 81(5).
  2. Brandt, Y. “High Points in Aerospace Physiology: A USAF Perspective, Part 2.” Aviation, Space, and Environmental Medicine (2010) Aug; 81(8).
  3. Brandt, Y. (2010) AOP History: Organizational History to 1971.

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