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This week we put a square mirror in the bathroom. In the process ended with a small crack in one corner, a sign we are not too "hands" and that reminded me as a square windows helped change the history of aviation.

The British De Havilland Comet was the first reactor passengers. Created in 1952 served as a standard of superior British aviation technology at that time, the Russians and Americans. Its beautiful design, with engines embedded in the wings, called the attention of passengers. Unfortunately, the designers decided, also for purely aesthetic reasons, the windows should be square.






Initially all went well. For two years he was the master of the skies as Boeing tried to complete the development of their first civil reactor, the 707 . And then disaster struck. After several accidents, and especially after two unexplained crashes in January and April 1954 it was decided to ground the rest of the planes to find out what was happening.

Al pressurized to simulate in a pool cycles of ascent and descent of the aircraft was discovered that, along with the corners of windows, cracks appeared in the fine aircraft fuselage. These cracks grew gradually until rupture and cause catastrophic depressurization of the fuselage. What was happening?

The phenomenon is known as " material fatigue." Known since antiquity but difficult to analyze and was not sufficiently taken into account. Basically consists of a material breach after applying a little effort, far less than the maximum rupture stress. In fact, this latest strain is the classic drop breaks the camel. To produce the rupture, the material has previously suffered a lot of effort in cycles. These forces accumulate cracks and dislocations in the structure of the material that eventually cause breakage. The result is difficult to estimate accurately but there are approximate formulas to calculate the length of the fuselage of an airplane, a bridge or other structure. And always good to proper maintenance to detect cracks before they grow too much.

Proper design also helps. The substitution of other oval square windows along with other structural improvements eliminated the problem of the Comet. Unfortunately he could not recover from the terrible loss of confidence that caused the accident. The Americans began to control the market until the arrival of Airbus .

is not the only case. When the calculations fail or maintenance accidents occur as the train derailment high speed the offshore dump or molasses massive floods that follow smelling for years. Better not overwhelmed by a simple mirror.

Category: Physical