When researching aircraft components, you may come across outflow valves. They are found in most airplanes certified to fly above 10,000 feet. Outflow valves play an important role in creating a safe, comfortable environment for passengers. What is an outflow valve exactly, and how does it work?
Overview of Outflow Valves
Outflow valves are devices that regulate the cabin pressure in airplanes. As the name suggests, they allow air to “flow out.” By regulating the flow of air out of the cabin, outflow valves help to maintain proper cabin pressure during flight.
Understanding Cabin Pressurization
The atmosphere is different at cruising altitude than ground level. Many airplanes fly at around 35,000 feet where the air is very thin. While the thin air reduces drag and promotes better fuel efficiency, it doesn’t provide sufficient oxygen for humans to breathe. This is why modern airplanes are designed with pressurized cabins.
Modern airplanes solve this problem by continuously pumping compressed air into the cabin. The cabin pressure is typically the equivalent of about 6,000 to 8,000 feet above sea — even when the airplane is flying at a cruising altitude of 35,000 feet. At this pressure level, passengers will experience a safe and comfortable environment.
Why Outflow Valves Are Necessary
Pumping compressed air into the cabin isn’t enough to maintain a safe and comfortable environment for passengers. Airplanes need an outflow valve to release excess air.
Atmospheric pressure changes rapidly when airplanes climb and descend. When climbing, the pressure outside of the airplane will decrease rapidly. When descending, the pressure outside will increase rapidly. Outflow valves manage pressure changes so that the cabin gradually adjusts to the appropriate pressure level.
How Outflow Valves Work
Most modern airplanes are equipped with one or two automatic outflow valves. Pilots enter flight information into a computer and it handles pressure management throughout the flight.
The computer will typically analyze the airplane’s altitude, vertical speed, atmospheric air pressure and other factors. Using this data, it will adjust the outflow valve to achieve the proper pressure level for the cabin.
While most outflow valves work automatically, some airplanes are equipped with manual valves. Manually operated outflow valves support pilot adjustments. Pilots can essentially change the outflow valve’s pressure settings by hand.
In Conclusion
Outflow valves are among the most important components of an airplane’s pressurization system. They continuously regulate the amount of air leaving the cabin, helping to maintain a safe and comfortable environment as the aircraft climbs, cruises and descends.
