Frequent flyers must have noticed a micro hole at the bottom part of the airplane windows. What is that and why for?
Let us answer the question for you
The tiny hole that are there in the airplane windows are called a breather or a bleed hole. It serves an important safety function in the aircraft.
Look carefully at the aircraft window, you’ll see three panes. All the panes are made up of acrylic materials. The innermost pane serves the purpose of protection and is also called scratch pane.
What’s the purpose of breather hole?
The middle pane contains the tiny hole which we’ve called the breather hole above. When the aircraft rises up in elevation, the air pressure drop in both the cabin and in outside air. But the pressure drop is much more outside as the aircraft’s pressurization system keeps the pressure inside the aircraft stable.
This means, at a height, the pressure inside an aircraft is much more than the pressure outside. Now the bleed hole comes into function. It allows the pressure to equilibrate between the cabin and the gap between the panes. Thus, all the cabin pressure is applied to only the outer pane.
In case a mishap happens and the outer pane fails, the middle pane will withstand the pressure. Although, some amount of air will leak through the breather hole, but the aircraft’s pressure system can easily bear with it.