The Guiding Stars

The maiden flight of the D-2 was made last week at Mather Air Force Base, Calif. Six skilled air navigators went through all the problems and perplexities of a mission in a jet bomber over the North Pole. They struggled with veering winds, lack of landmarks, and the odd behavior of magnetism and celestial bodies in the polar regions. All this they did without leaving a windowless concrete building that contains a reasonable facsimile of the starry firmament on high.

The new D-2 High-Speed High-Latitude Celestial-Navigation Trainer was specially designed by Link Aviation Inc. to simulate the flights of jet bombers over the arctic, where the magnetic compass is practically useless and the sun often out of sight.

Inside the building, which is roughly cubical and 61 ft. long, is a three-quarter sphere made of a spidery crisscross of thin-walled steel lined with wire mesh. The whole thing, 30 ft. in diameter, is mounted so that it can be tilted 65DEG in any direction. It can also revolve, and a platform poking up to its center can revolve independently.

Off for Greenland. On the inside surface of the sphere are 507 tiny lights that simulate all the conspicuous stars in the sky. Even the colors of the most important stars are matched by means of niters. When the student of air navigation stands on the little platform, he sees overhead with almost frightening realism the enigmatic points of light that will be expected to lead him in wartime around a blacked-out world. For daytime flights the stars are extinguished, and a single light plays the part of the sun.

Each student navigator sits in a booth below the starry sphere. Above his desk are instruments that tell the air speed, altitude, gyrocompass reading and other flight data about the airplane he is supposed to be navigating.

The instructor sitting at his control console decides where the mission shall start. By setting the apparatus, he can fly the desk-bound students anywhere he pleases in the northern hemisphere. As the simulated bomber heads for Alaska. Petropavlovsk or Greenland, the chicken-wire dome with its pinpoint stars wheels and tilts slowly just as the real stars would seem to do from the observation window of a real bomber.

The student knows his take-off point. He knows where his ship is supposed to go, and roughly how fast and in what direction it is flying. His job is to find out, by observation, where it really is. Such factors as wind and misbehavior of the gyrocompass can make the ship wander far off its course.

Sun on the Arctic. At the instructor's command, each student climbs the spiral stair that leads to the platform inside the dome. He glances up at the simulated stars and selects the ones he thinks will guide him best. He observes their position with a sextant, just as he would on a real airplane, and hurries back to his desk to figure out his position over the Canadian tundra or the frozen Polar Sea.

The Ds's flight last week was an unusually tough one. Captain Warren Harris, chief instructor, announced that it would start from Norway, fly to Greenland, then fly near the North Pole to drop supplies for an aircraft downed on the arctic ice. This was to be done in daylight and at a time of year when the sun is always showing in the polar sky. Navigators much prefer the night when the stars are visible. A "three-star fix" tells them much more about their position than the sun alone can do.

To make the job even harder. Captain Harris kept throwing unscheduled troubles at the students. He changed the wind, the air temperature, the air speed of their airplane. All went fairly well until the flight was near the North Pole. Then all the skilled navigators got thoroughly lost. Investigation showed that the machine had not been set to make the wind have the proper effect on the motion of the airplane. The experienced navigators had compensated for the wind; the inexperienced machine had not. Result: the plane had blown far off its course. Such kinks will be eliminated, says Captain Harris, by the time the regular student-navigators try their simulated wings over the North Pole.

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