You settle into your window seat, relax, and gaze out the window. Then you notice a tiny hole near the bottom. You notice that no air enters that tiny hole as you fly higher and higher. That tiny hole you see does not extend all the way through the aircraft, and it serves a purpose. Bleed holes are those tiny holes on airplane windows that are there for safety reasons.
The pressurization system on board an aircraft
Before I get into why those holes are there, let me explain what happens at 31,000 feet. The oxygen level decreases as you ascend higher and higher. Have you ever noticed that as you climb higher in the mountains, you get a little queasy? This is because the oxygen level at higher elevations is lower than at sea level. Hypoxia, which can be fatal, can result from a lack of oxygen.
How come you don’t feel anything when flying in an airplane, even if you reach altitudes of 30,000 feet or higher? Because an airplane cabin is pressurized as it climbs higher, passengers can breathe normally. This is beneficial to passengers because engine air is pumped into the cabin to simulate the oxygen level we breathe when flying at normal altitudes. The pressurization system of an aircraft is beneficial to the passengers, but it is detrimental to the aircraft’s cabin and fuselage if it cannot bleed.
Airplane windows
The windows on an airplane are made up of three panes. The first or inner pane is the one that can be touched or knocked on. The second pane has a tiny hole in it. The third pane is the outer one, and it protects us from the outside pressure difference. At 35,000 feet, there is a significant difference in pressure between inside and outside.
The tiny hole relieves pressure on the middle pane, allowing the outer pane to take all of the cabin pressure. As a result, it allows pressure to bleed out, balancing the air pressure between the middle and outer panes. Apart from allowing air pressure to bleed, the bleed hole also allows moisture to escape between the second and third panes, preventing the window from fogging up.
So, the next time you fly, remember that when you look out the window, you’re actually looking through three window panes. At the same time, that hole inside the cabin into which you can insert the ballpen tip is not present. It is found on the second pane.
First love never dies. I fell in love with airplanes and aviation when I was a kid. My dream was to become a pilot, but destiny led me to another path: to be an aviation digital media content creator and a small business owner. My passion for aviation inspires me to bring you quality content through my website and social accounts. Aviation is indeed in my blood and blog!
