Jet Assist

Ships steaming across the North Atlantic from west to east like to keep in the Gulf Stream, which increases their speed by a knot or so at no cost. Pan American's Stratocruisers, flying from Tokyo to Honolulu, are taking the same advantage of the "jet stream," which is the Gulf Stream of the upper air. Last week one of Pan Am's clippers made the Tokyo-Honolulu run in a record 9 hr. 18 min. Its average, point-to-point speed was 422 rn.p.h., and 123 m.p.h. was a gift of the friendly jet stream.

The North Pacific jet stream was discovered during World War II. It is formed when a cold air mass from the Arctic or Siberia meets warm air from the south, and it often moves faster than 250 m.p.h. To Pan Am, it looked like a pot of gold. Pan Am's regular route from Tokyo to Honolulu required a fuel stop at Wake Island. The dog-legged course was 4,320 miles long and took more than 17 hours. With a boost from the jet stream, Pan Am reasoned, the hop might be made nonstop, saving 450 miles and covering part of the distance free on the river of wind.

Shaken Rope. The jet stream is not like a surface river, confined between solid banks. It whips around like a shaken rope, and to predict its position, speed and direction takes both knowledge and skill. Pan Am gathered all available data and added observations of its own. Last year, its meteorologists felt they knew enough to take the plunge. The Stratocruisers were regularly scheduled to fly nonstop from Tokyo. The first flight made Honolulu in 11 1/2 hrs. instead of 17.

Since then, Pan Am has developed an elaborate technique of air hitchhiking. Before each flight from Tokyo, meteorologists figure out where the jet stream is going to be and how much help can be expected from it. The ship is loaded accordingly (more help, more payload), and the captain is told what course to fly. Generally he climbs into the stream at 17,000 ft. half an hour out of Tokyo. As knowledge accumulates, more flying time is saved. Now each airplane hitched to the jet stream "finds" 2,200 gallons of free gas in the sky.

The jet stream is no good in summer; it flows too far to the north. East of Honolulu, it is present but not dependable, and on east-west flights it is a hindrance rather than a help. When headed west, Pan Am still schedules the Wake Island stop.

425 Knots. Pan Am's observations are carefully studied by the Air Force. Though usually strongest over the North Pacific, the great stream blows around the earth, changing drastically the flying distance from point to point. Knowledge of its habits would make all the difference in successful bombing expeditions. Since the stream is strongest at 35-40,000 ft., only high-flying military airplanes could make full use of it at present. For them and for future jet liners, its possibilities are striking. Two weeks ago, the stream was clocked at 425 knots (489 m.p.h.) over Spokane. If a 6-47 had climbed into it, it might have flown to New York in 2 1/2 hrs.

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