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The Airplane Designers

A. There are two main things that make aircraft engineering difficult: the need to make every component as reliable as possible and the need to build everything as light as possible.

B. Given a certain power of engine and a certain fuel consumption, there is practical limit to the total weight of aircraft, that can be made to fly. Out of that weight as much as possible is wanted for fuel, radio navigational instruments and, of course, for passengers or freight themselves. So the structure of the aircraft has to be as small and light as safety and efficiency will allow. The designer must calculate the normal load that each part will bear. This specialist is called the “stress man”.

C. The stress man’s calculations go to the designer of the part, and he must make it as strong as the stress man says. One or two samples are always tested to prove that they are as strong as the designer intended. Each separate part is tested, then a whole assembly – for example, a whole wing, and finally the whole airplane. When a new type of airplane is being made normally only one of the first three made will be flown. Two will be destroyed on the ground in structural tests. The third one will be tested in the air.

D. Two kinds of ground tests are carried out. The first is to find the resistance to loading of the wings, tail, etc. until they reach their maximum load and collapse. The other test is for fatigue strength. Small loads are applied thousands of times. Each may be well as a single load, but many repetitions can result in collapse. When a plane has passed all the tests it can get a government certificate of airworthiness without which it cannot fly.

E. Making the working parts reliable is as difficult as making the structure strong enough. The flying controls, the electrical equipment , etc. must not only be light in weight, but must work both at high altitudes where the temperature may be below freezing point and in the hot air in the tropics.

F. To solve all these problems the aircraft industry has a large number of research workers, with elaborate laboratories and test houses. And new materials to give the best strength in relation to weight are constantly being tested.

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