Question

Why do all aircraft windows have a tiny hole in them?

• A. For easily cracking the window in case of emergency.
• B. For better ventilation in the aircraft.
• C. It helps in regulating the temperature of the aircraft.
• D. To equalise pressure between the two panes of the window.

Answer 1

The correct option is D To equalise pressure between the two panes of the window.

Before we give the reason as to why there are tiny holes on aircraft windows, let's have a look at a cross-section of a window of an aircraft. If you notice closely at a passenger cabin window, you would see three panes. The tiny hole exists on the middle pane, surrounded by the exterior and the interior panes. The air pressure is greatly reduced as we go higher up the altitudes, thereby creating a pressure difference between the air outside and the air inside the cabin.


It could prove fatally dangerous if this pressure difference is not regulated! These tiny holes, also called breather holes, serve as a safety function, by making sure that the outer pane bears all the air pressure (the pressure inside the cabin is much higher than outside). This also ensures that in case the pressure difference becomes high enough, it is the outer pane that breaks off first. In addition to this, the breather hole also removes the moisture that is trapped between the inner and outer panes so that your window remains free of fog. Imagine an otherwise foggy window which obstructs your view when you're flying!