why do aircrafts have oval windows?

Question

i have to make a project and need to show the use of windowsof alternate shapes in aircrafts

Answer 1

Round windows provide a more even force (pressure) distribution then a rectangular.
Also round windows allow a better gasket seating for pressurized cabins.

An average window is 0.09677 m^2
1 atmosphere is 101.325 kPa (kN/m^2) (There is very little pressure above 30, 000 ft [almost Mount Everest] where the pressure is 1/3 of the 1 atmosphere)
F= P A= (2/3) 101325 n/m^2 x 0.09677 m^2 = 6537 N

This a weight equivalent to 666 kg of mass! (10 average people)

Answer 2

As was already stated, to prevent cracks. Cracks can easily grow under stress, especially oscillating stresses which are common to the routine pressurization and depressurization of aircraft cabins.

Cracks are a very big deal on airplanes. There is a critical crack length in a pressurized system which will cause the system to explode i.e. the crack to propagates at the speed of sound in the medium and system pressure blows it up. Think about the popping of a balloon. If you put a pinhole when the balloon is not under a whole lot of pressure, it won't blow up but you get to a point very quickly will it will violently explode.

We found out about this the hard way in aviation. The british Comets were exploding after X number of flights because the spacing of the spars were more than the critical crack length.

Answer 3

Most are round or square or rectangular, they may appear oval, there may be some oval, and you may have seen them on the aircraft in your area.

If Square or rectangular then, they have rounded corner. This is to remove sharp corner and stress points and cuts in case of a mishapping.

There is a specification written that requires that as far as possible any thing that is space and airworthy, should not have any sharp corners.

Some times it not possible to round the corners off in that case a non conformance report needs to be written and submitted to FAA(or any other agency in the country of manufacturing) and it must be approve by them.

By the way lots of countries have adopted FAA specifications entirely, rather then produce their own specifications.

If the windows are Small and that is the case most of the time then rounding the corners makes them appear oval.

Answer 4

Sharp corners are eliminated on the windows to reduce the stress concentrations and that in turn helps prevents cracking of the material.

Answer 5

I saw a program about early airplanes once and they said it gives the fuselage more strength. A square one would weaken the sides of the plane.

Answer 6

They can stand pressurization better than square ones.
The wind shield is curved to reduce wind Resistance on also to help deflect birds that may hit it.

Answer 7

They did have square windows at one time but cracks would propagate from the corners (not good).

Answer 8

cauz squar encourages us to jump out side

Answer 9

hi good question
you will get good answer