Cabin pressurization

Cabin Pressurization

Cabin pressurization is a process used in aviation to maintain a safe and comfortable environment for passengers and crew inside an aircraft flying at high altitudes. This system is crucial for ensuring that the cabin air pressure is kept at a level that is safe for human physiology, despite the low pressure of the outside atmosphere at cruising altitudes.

Overview

Aircraft cabins are pressurized to simulate the atmospheric conditions found at lower altitudes, typically equivalent to the air pressure at 6,000 to 8,000 feet above sea level. This is necessary because at cruising altitudes, which can exceed 30,000 feet, the atmospheric pressure is too low to support human life without supplemental oxygen.

The pressurization system works by using air that is bled from the engines, which is then cooled, filtered, and pumped into the cabin. The cabin pressure is controlled by an outflow valve that regulates the amount of air that is allowed to escape, maintaining the desired pressure level.

Physiological Effects

Maintaining cabin pressure is essential for preventing hypoxia, a condition where the body is deprived of adequate oxygen supply. Symptoms of hypoxia can include dizziness, fatigue, and in severe cases, loss of consciousness. By pressurizing the cabin, the risk of hypoxia is minimized, allowing passengers and crew to breathe normally.

Cabin pressurization also helps to prevent decompression sickness, which can occur when the body is exposed to a rapid decrease in pressure, causing nitrogen bubbles to form in the bloodstream.

Technical Aspects

The pressurization system is an integral part of an aircraft's environmental control system (ECS). It includes components such as:

• Bleed Air System: Takes air from the engine compressors.
• Air Conditioning Packs: Cool and condition the bleed air before it enters the cabin.
• Outflow Valve: Controls the cabin pressure by regulating the air leaving the cabin.
• Pressure Controllers: Automatically adjust the outflow valve to maintain the desired cabin pressure.

Safety Considerations

Aircraft are designed with multiple safety features to handle pressurization failures. In the event of a rapid decompression, oxygen masks automatically deploy to provide passengers with supplemental oxygen. Pilots are trained to descend to a lower altitude where breathable air is available.

Also see

• Hypoxia (medical)
• Decompression sickness
• Environmental control system
• Aviation safety