Why airplane windows are round ?

Ever wondered why airplanes windows are round and not squared ? It’s the reason.

Airplanes have been the centre of attraction from time immemorial. The greatest achievement of man kind. From our humble beginning with unpowered gliders to the jet powered aircrafts that carry thousands of passengers everyday.

The first jet aircraft, deHavilland’s Comet had square windows. First flown in 1949, it revolutionised the air. It was the first commercial jet aircraft and it can fly higher and faster than any other aircraft at that time by flying at 30000 ft and 50% faster than its competitors. Most of the airlines such as Air India, Pan AM, Japan Airlines had order for one of these aircraft.

deHavilland Comet with square windows.

But just as everything was going fine, Flight 781 and Flight 201 crashed due to mid-air breakup of the aircraft. 56 people lost their lives as the result of structural failure that occurred in the aircraft. Further investigation blamed the square windows as the cause for the accident.

The comet was the first aircraft to fly at 30000 ft higher than any commercial aircraft. Due to its high flying nature, the aircraft cabin needs to be pressurised and de-pressurised during every take off and landing. As a result, the aircraft faced structural stresses higher than any other plane in the sky. Every pressurisation and de pressurisation put more and more stress on the aircraft’s structure. The square windows became the weak point in the sky. Sharp corners are natural weakspots where stress concentrates, weakened further by air pressure. When subject to repeated pressurisation, cracks developed around the square windows and resulted in disaster.

Curved windows on the other hand, has no focal point. The stresses are distributed equally around the windows reducing the likelihood of cracks. Circular shapes are also stronger and resist deformation and can survive extreme differences in pressure between outside and inside of the aircraft.

The deHavilland comet’s popularity never recovered. Orders were cancelled and by time other manufactures such as Boing took the spot of deHavilland. But still, it remains one of the greatest discoveries of mankind.

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