Why are airplane windows round, not square?

You may have noticed that they are round or oval in shape rather than square if you have ever looked out of an aeroplane window. This seemingly straightforward design decision has an intriguing, life-saving history that stems from physics and engineering.

The Issue with Square Windows

It’s true that aeroplane windows were square in the early days of flight. In order to enable higher, quicker flights, manufacturers experimented with pressurised cabins in the 1950s while passenger aircraft like the British de Havilland Comet were created. But the original Comet planes had disastrous malfunctions that resulted in multiple fatal crashes. Until they discovered a crucial defect—the windows’ shape—investigators were baffled.

It turns out that these mid-air catastrophes were directly related to square windows. To keep passengers comfortable, the cabin of an aircraft pressurises as it ascends. The fuselage of the aeroplane experiences tension as a result of this pressure differential. Square windows’ sharp corners concentrated tension and served as weak spots. These regions were vulnerable to metal fatigue over time, which ultimately resulted in structural failure and, sadly, crashes .

Why Round Windows Work

Because round or oval windows don’t have sharp corners, the tension is dispersed more uniformly throughout the window’s borders. The structure is far more resistive to pressure because of its continuous, smooth shape, which lowers the possibility of weak spots. In engineering, this idea is referred to as “stress concentration.” Round windows keep too much stress from building up at any one point, extending the lifespan of the aircraft’s fuselage and improving safety for everyone on board.

The Physics Behind the Choice

With each trip, the cabin of an aeroplane is pressurised and depressurised. This results in a “cyclical load,” where stress levels fluctuate between high and low. While rounded windows may effectively withstand load cycles, square windows’ corners cannot withstand these repeated loads without deteriorating. Through thousands of takeoffs, flights, and landings, round windows contribute to the structural integrity of the aircraft by spreading the stress equally.

A Simple Change with Big Impact

Following the de Havilland Comet investigations, the switch from square to round windows became commonplace in aviation design. These days, most passengers don’t even consider it because it’s such an important safety component that’s so effectively incorporated into aircraft design. This minor change has made a huge difference to modern aviation safety standards.

Aeroplane windows’ circular shape is a clever yet straightforward design solution to a potentially fatal problem. The technical marvel that appears to be an aesthetic decision serves as a reminder of how important careful design is to maintaining our safety at 30,000 feet.

Therefore, keep in mind that it is protecting you the next time you gaze out of that circular aeroplane window.