Broadly defined, this subdiscipline endeavors to discover and prevent various adverse physiological responses to hostile biologic and physical stresses encountered in the aerospace environment. Problems range from life support measures for astronauts to recognizing an ear block in an infant traveling on an airliner with elevated cabin pressure altitude. Aeromedical certification of pilots, aircrew and patients is also part of Aviation Medicine. A final subdivision is the AeroMedical Transportation Specially. These military and civilian specialists are concerned with protecting aircrew and patients who are transported by AirEvac aircraft (helicopters or fixed-wing airplanes).
Atmospheric physics potentially affect all air travelers regardless of the aircraft. As humans ascend through the first 9100-18,300 m (30,000-40,000 ft), temperature decreases linearly at an average rate of 2ºC (3.6ºF) per 305 m (1000 ft). If sea-level temperature is 16ºC (60ºF), the outside air temperature is approximately -57ºC (-70ºF) at 10,700 m (35,000 ft). Pressure and humidity also decline, and aircrew are exposed to radiation, vibration and acceleration forces...the latter is also known as "g" forces. Aircraft life support systems such as oxygen, heat and pressurization are the first line of defense against most of the hostile aerospace environment. Higher performance aircraft will provide more sophisticated life support equipment such as "G-suits" to help the body resist acceleration, and pressure breathing apparatus or ejection seats or other escape equipment.
Every factor contributing to a safe flight has a failure rate. The crew of an aircraft is no different. Aviation medicine aims to keep this rate in the humans involved equal to or below a specified risk level. This standard of risk is also applied to airframe, avionics and systems associated with flights.
AreoMedical examinations aim at screening for elevation in risk of sudden incapacitation, such as a tendency towards myocardial infarction (heart attacks), epilepsy or the presence of metabolic conditions diabetes, etc which may be lead to hazardous condition at altitude. The goal of the AeroMedical Examination is to protect the life and health of pilots and passengers by making reasonable medical assurance that an individual is fit to fly. Other screened conditions such as colour blindness can prevent a person from flying because of an inability to perform a function that is necessary. In this case to tell green from red. These specialized medical exams consist of physical examinations performed by an Aviation Medical Examiner or a military Flight Surgeon, doctors trained to screen potential aircrew for identifiable medical conditions that could lead to problems while performing airborne duties. In addition, this unique population of aircrews is high-risk group to several diseases and harmful conditions due to irregular work shifts with irregular sleeping and irregular meals (usually carbonated drinks and high energy snacks) and work-related stress.
Anything in the system can fail in two ways. Passive failures occur when something stops working. Examples would be an artificial horizon stops working and a flag shows that it has failed or a pilot who loses consciousness. Active failures occur when the item continues to function but in an incorrect manner. Examples would be a trim motor which kept going after the switch was released or a pilot who develops psychotic thinking and behaves in response to that.