Science: Automatic Dead Reckoning

The dead reckoning that oldtime sailors used in bad weather when they could not shoot the sun has a modern counterpart “in Ryan Aeronautical Co.’s recently announced long-range air navigation system. The sailors estimated their speed, leeway and the effect of ocean currents to give them their rough position. The Ryan Automatic Navigator does much the same thing by making a fix on some object whose position is known (e.g., the Pentagon). While still within radar range, the instruments tell the ground speed, etc., by radar observations. With increasing distance, the instruments operate on their own, by sensing delicately each force that tends to divert the airplane from its proper course. A crosswind, for instance, is felt as a push from one side, and its effect is evaluated. All the deviations are “integrated” (put together and added up) by electronic computing devices. So the pilot, says Ryan, always knows where he is.

Another new gadget that does dead reckoning for aircraft is made by Ford Instrument Co. Simpler than the Ryan job, it estimates the effect of the wind in advance. Then it records the air speed and the course the airplane follows. It puts the whole thing together and figures out the airplane’s position on a map. Average accuracy on a 1,000-mile flight: within about six miles.