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Student pilots learn to fly in thin air

TYNDALL AFB, Fla. -- A pilot is cruising along at 30,000 feet in an F-15 Eagle when suddenly he begins to feel "different." He gets light-headed and his vision starts to blur. What is going on? 

That question is answered when F-15 B-Course students go through physiological training in the altitude chamber. 

Aviators have long known about the effects of high altitude flight on the human body, specifically what happens when the body doesn't get enough oxygen, but it wasn't until about 50 years ago the Air Force adopted a physiological training program to teach pilots how the body reacts to the stresses of flight. 

One such stress is hypoxia, a condition in which the body is in an oxygen deficient environment, such as flying at high altitudes where there are fewer oxygen molecules. If the condition is not immediately recognized and corrective actions taken, the results can be disastrous. 

Staff Sgt. Rodrigo Vener, 325th Aeromedical-Dental Squadron aerospace physiology technician, said the symptoms of hypoxia vary from person to person. Other physiological factors will also effect the onset of hypoxia. 

"For a healthy individual flying at 18,000 feet, the time of useful consciousness (the period of time which a person retains normal motor functions) is about 30 minutes, but is reduced to three to five minutes at 25,000 feet, Sergeant Vener said. "If the same individual smoked, didn't exercise and maintained an unhealthy lifestyle, his time of useful consciousness would be reduced." 

Teaching students about hypoxia, and letting them actually experience it, would be difficult if the only way to get the experience was to fly. Fortunately, the 325th ADS has an altitude chamber, which is a small room-sized structure that resembles a contraption out of a 1950s science fiction movie. 

Inside the chamber, each student is seated at a console with an oxygen regulator. To eliminate any confusion on procedures during actual flight, the regulators in the chamber are exactly the same type as those used in Air Force aircraft. 

The students don their helmets and oxygen masks, are given a briefing and the door is sealed. Air is removed from the chamber simulating an increase in altitude. Once they reach the target pressure altitude, students remove their oxygen masks and are given a series of written puzzles to figure out. 

Having trouble with mental reasoning is a symptom of hypoxia, so the students' performance while completing the puzzles is monitored closely by instructors. 

Students are taught to gang-load their oxygen regulators by moving all switches at once to provide 100 percent oxygen, which is delivered under pressure. They are also taught to fasten their oxygen masks if they begin to feel any symptoms of hypoxia. 

"Teaching the students to gang-load their regulators is a critical part of the training," Sergeant Vener said. "If hypoxia sets in and the pilot immediately sets his regulator to deliver 100 percent oxygen under pressure, he will recover within 30 to 60 seconds. But, if the pilot doesn't get the oxygen turned on or the mask up, he could pass out and be unable to recover the aircraft." 

According to Maj. Brian Biebel, 95th Fighter Squadron, assistant director of operations, a rare but possible cause of oxygen deficiency in fighter aircraft is decompression, a condition in which there is a loss of the atmospheric pressure maintained in the cockpit.
"Failures in a system on the jet that could cause decompression could be difficult to recognize, so pilots must be able to recognize the symptoms of hypoxia as soon as they begin," said Major Biebel. 

By becoming aware of these symptoms in training, pilots can recover in the air.