AS9120B, ISO 9001:2015, and FAA AC 0056B ACCREDITED

How Strong Are Airplane Windows and What Are They Made Of?

An airplane cabin window consists of three panes: an outer pane that sits flush with the outside fuselage, an inner pane which has a noticeable small hole in it, and a thinner, non structural plastic pane called a scratch pane. This means that passengers are not able to touch the inner or outer panes, but are able to interact with the scratch pane. While these three panes are all quite different in their roles, they are all made of a material called “stretched acrylic,” a substance that is stronger and more lightweight than glass. More specifically, it provides better resistance to cracking and impact, making it an excellent option for use in aviation.

One major trait unique to each pane is its thickness. Whereas the inner panes are generally thinner at approximately 0.2” thick, the outer pane is usually about 0.4” thick, allowing it to carry large pressure loads throughout the window’s service life. As with countless other components on board, the main role of the inner pane is to serve as a fail-safe if the outer pane were to fail. However, it is also helpful for equalizing the pressure difference between the air in the cabin and the plane’s exterior. For this reason, the inner pane has a small hole at the bottom which allows the free movement of air from inside the cabin to the space within the approximately 0.25” gap between the inner and outer panes.

As a plane gains altitude, the pressure acting on the outside of the vessel drops, so the air within the cabin must be pressurized for passenger comfort. This inside pressure is bearing on the fuselage and cabin windows, so the small hole on the inner panel allows some of that air to escape into the pocket between the inner and outer panels and equalize. As a result, this forces the more durable outer pane to bear the load over a slow period of time accounting for how long it takes for air to seep through the inner pane.

For this system to work, the scratch pane covering the inner pane does not block air from escaping into the inner pane hole, allowing it to freely flow through multiple gaps into the interior assembly. Without these important design features, the sudden force of changing pressure could push on the scratch pane or inner window, causing microfissures and other signs of wear. Another key feature of airplane windows is the rounded design. Whereas the windows of your home or office have the choice of different shapes, airplane windows are always rounded for the sake of greater structural integrity.

With all of these design features combined, aircraft windows are extremely durable and resistant to wear, but how well would they handle a gunshot? While there may be some myths out there about their strength, airplane windows are typically not bulletproof. Though they feature much thicker glass than the window of a car or building, the stretched acrylic they are made of is able to resist blunt impact, but are not strong enough to withstand bullets.

While airplane windows may not be bulletproof, they are able to take a lot of force as a result of their carefully tried and tested design. For access to airplane windows that have been tested for fit and function, you can rely on NSN 360 for all your procurement needs. Hosting a vast inventory of aircraft components from a widespread network of trusted manufacturers located across the globe, we are well-equipped to offer premium service as your sourcing partner. Get started today when you browse our online catalog of available parts or send an RFQ form with details about your operational needs. Our dedicated team of experts is available 24/7x365 to answer customer inquiries and requests, so you can expect a response within just 15 minutes of sending a completed RFQ form.


September 19, 2022
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