Slots for Drag

The earliest airplane designers knew that air turbulence was their enemy, tried to build wings that would slip through the air as smoothly as fish drift through water. They always failed. As the air flowed over the wing, it broke into curling eddies that dragged at the plane and drank up the engine's power. In theory, the scientists knew that this "burble" effect could be prevented by sucking into the wing a thin layer of air, and with it the incipient eddies. The remaining air would glide past the whole wing in smooth "laminar flow" (see diagram).

This long-discussed system remained largely a dream for 50 years. But last week Northrop Aircraft, Inc. recorded the results of seven years of experimentation with "low drag boundary layer control." After elaborate tests with models in wind tunnels, Northrop engineers fitted the wing "of an F94 jet fighter with a "glove" containing twelve slots running lengthwise along the wing. A suction pump driven from the main engine pulled air into the slots and pushed it out astern with the rest of the jet's gases, adding a little to the thrust. The reduction of drag was extraordinary, even when the power consumed by the pump was added as drag. A more advanced system with 69 slots worked even better.

Vice President Edgar Schmued of Northrop thinks that B.L.C. (Boundary Layer Control) will be the next great advance in airplane design. It will be most useful in long-range airplanes, since Northrop's figures indicate that the range of any B.L.C. airplane should be almost double that of a "turbulent" plane of the same weight.

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