Give and Take

FLYING over the Grand Canyon from Los Angeles our plane hit some nervous air. I put down my paper and looked out. The wing was flapping like a seal before breakfast. In the wing tip there was an up-and-down waggle of at least a yard. I did not feel quite as bold as a lion. After we got to LaGuardia Field--all right and on time--I mentioned that wobble to our pilot. "Oh sure," he said, "that's built in on purpose. Matter of fact, what you saw was just a little flicker. Sometimes she really flaps, as much as six feet or more. All built in. Have to have elasticity, you see. If the wing was rigid, it could snap." "Have to have some 'give' in it," I said. "Yes," he went on, "some 'give' and also some 'take.' " On the drawing boards they have a fancy engineering name for it. They call it tolerance. That just means the amount you have to give or take under stress before you snap. If you're rigid, you see, something unexpected comes along and hits you hard, maybe across your grain, and you snap. That's not good. So what they call tolerance in engineering turns out to be only give and take. And it can be built in. Into the cold end of an aluminum wing. . .or into a human heart.