Comet 1 Traffic Analogy Audio Transcript

As an airplane takes off and lands, the fuselage pressurizes and de-pressurizes. The more pressure, the more stress load on the fuselage. This stress load can affect different shapes in the aluminum structure of the airplane by different amounts. Modern window shapes are designed to minimize the effect of the stress load. But Comet windows were designed squarish without knowing how severely this would affect the stress. Modern windows provide a fairly smooth distribution of stress around the gradual corners of the window, but on the Comet, the stress builds, or concentrates, around the abrupt corners.

Think of it like traffic flowing around the windows. In low-flow situations for stress or traffic, the two types of corners are fairly similar. Traffic does not have any trouble merging into one lane to get around either set of construction cones. In high-flow situations, both traffic and stress react very differently from low-flow. When the gradual road block is encountered, there’s some back up to get everyone merged into one lane, but it doesn’t have to be an ordeal. Traffic congests but generally everyone stays moving.

For the abrupt road block, traffic comes to a halt because there was no warning of the forced transition. The same number of cars are all trying to get through which ever way the road block is set up, but providing no transition distance significantly worsens the situation.

The traffic congests most at the point where the merge must happen – at the corner of the roadblock, or at the corner of the squarish window. For the Comets, the stress concentrations at the squarish window corners fatigued the fuselage material so severely, that it caused the ruptures of the aircrafts at Elba, at Naples, and in the water tank test.

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