What you measure and what you seek to control

An excellent parable on the goals to set when looking to the future. In the coming years, this story should be on the minds of anyone working in the autonomous vehicle space.

Britain was set to dominate the jet age. In 1952, the de Havillands Comet began commercial service, triumphantly connecting London with the farthest reaches of the Empire. The jet plane was years ahead of any competitor, gorgeous to look at, and set new standards for comfort and quiet in the air. Then things went horribly wrong.

In 1953 a Comet fell out of the sky, and the crash was attributed to bad weather and pilot error. …In 1954, a second Comet fell out of clear skies near Rome. The fleet was grounded for two months while repairs were made. Flights then resumed with the declaration, ‘Although no definite reason for the accident has been established, modifications are being embodied to cover every possibility that imagination has suggested as a likely cause of the disaster. When these modifications are completed and have been satisfactorily flight tested, the Board sees no reason why passenger services should not be resumed.’ Four days after these words were written, a third Comet fell into the sea out of clear skies near Naples, and the fleet was grounded again indefinitely.

…As the Comet accident report was being released in 1955, a little-known military contractor in the northwest corner of the United States was completing its prototype for a civilian jet airplane. Boeing had had little success with civilian craft in the past. The company knew that cracks had brought down the Comet, and they had better understand them before they brought down the Boeing 707.

Boeing brought in a researcher for the summer, Paul Paris, a mechanical engineer who had just finished a Master’s degree and was pursuing graduate studies at Lehigh University. …The view of fracture Paris brought to Boeing was dramatically different from the one that had guided construction of the Comet. Cracks were the centerpiece of the investigation. They could not be eliminated. They were everywhere, permeating the structure, too small to be seen. The structure could not be made perfect, it was inherently flawed, and the goal of engineering design was not to certify the airframe free of cracks but to make it tolerate them.[Emphasis added.]

The essence of algorithm design is not to eliminate all error, but to make results robust in the face of error. Where de Havillands tried in vain to engineer a plane where the materials were strong enough to resist all cracks and fatigue, Boeing realized that the right approach was to engineer a design that allowed cracks, but kept them from propagating so far that they led to catastrophic failure.

Michael Marder via O’Reilly.

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