Types of Aircraft Pressurization Systems
Cabin pressurization is the most effective method of ensuring aviators are not exposed to pressures beyond the physiologic zone. Types of pressurization systems include the Isobaric system and the Constant differential system(Aviation Medicine, 2011). The former is where the pressure in the cabin remains constant as the ambient pressure decreases with flight altitude while the latter is where pressurization begins at a particular altitude and cabin pressure is limited by a preset differential pressure value.
Key Components of Pressurization Systems
Heat exchanger- cools the hot pressurized air.
Outflow valve- regulates the amount of pressurized air leaving the cabin. Malfunctioning could lead to uncontrolled decompression.
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Safety valve- opens at a predetermined pressure to prevent cabin over-pressurization.
Negative pressure-relief valve- prevents cabin pressure from going below ambient air pressure preventing conditions like hypoxia and decompression sickness.
Dump valve- releases all cabin pressure when an aircraft lands.
Cabin Altitude
This is the cabin pressure expressed as an equivalent altitude above sea level. The percentage of oxygen in the air at high altitudes is similar to that at sea level. However, there is less pressure at high altitudes leading to a reduced amount of oxygen available in a given breath. This is why pressurization is done to simulate a lower altitude within the cabin. The cabin altitude is also critical in ensuring the structural pressure differential limitation is not exceeded. The cabin altitude of a commercial airline is maintained at 1800-2400 meters above sea level. Consequently, less oxygen is absorbed by blood cells and gases inside the body expand. When the blood takes up less oxygen, healthy passengers can tolerate the symptoms.
References
Aviation Medicine. (2011,March,3). Flying Into Thin Air: Preventing Hypoxia. Retrieved from http://www.avmed.in
