Weather Measure

Unlike most airplane pilots, ex-Marine Reuben Snodgrass waits expectantly for bad weather. When the clouds crowd down, or sea fog rolls in over Long Island's MacArthur Field, Rube and his crew crank up the Sperry Gyroscope Co.'s DC-3 and take to the air.

Time after time, the flyers circle the field on instruments and slant into cautious approaches to the landing runway. An auto-pilot steers them along the ILS (Instrument Landing System) beam. But while they are making their automatic approach, Rube and his copilot keep up a constant chatter on the radio. They sing out when they first spot the ground, report familiar landmarks, announce the first gleam of runway lights. And every word is recorded on the ground.

Meanwhile, a movie camera peeks over the pilot's shoulder, keeping one more record of what can be seen through the windshield. Bulging below the plane's nose, a still camera points toward the ground and snaps a picture every two seconds.

On the ground, a crew of technicians is just as busy. Before each landing, one man is at runway's edge, peering through the mist to count all he can see of a curving line of carefully placed black panels. Another sets up a stepladder at runway's end, climbs to the top (where he is almost as high as if he were in the cockpit of a landing plane) and counts the runway lights and markers that gleam through the weather. What each man sees is one more measure of visibility on the field. Automatic instruments keep a continuous record of wind, temperature and fog density.

A short distance from the runway, a 240-watt searchlight circles slowly, its narrow beam arcing day and night across the base of low-lying clouds. Only 200 feet away, a parabolic mirror points overhead to gather the searchlight's reflected glow and focus it on a photoelectric cell. As the clouds rise or fall, reflections vary. In the radio shack, remote-reading indicators record the angle at which the searchlight beam bounces back. Measuring cloud height is then a matter of simple trigonometry.

With all this activity and gathering of statistics, Sperry, the Air Navigation Development Board and the U.S. Weather Bureau are learning all they can about the tense last moments of an instrument approach to a socked-in airfield. Today's blind-flying planes have intricate instruments to help them navigate (TIME, June 15). But only the most accurate observations can tell pilots when it is safe to grope through mist toward the ground. In their dangerous flights over Long Island, Rube Snodgrass and his crew, measuring those last few feet of weather, are setting new standards for tricky, foul-weather landings.

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