Research Into Use Of Jet Streams

Press, Volume XCIV, Issue 28130, 20 November 1956, Page 8

Research Into Use Of Jet Streams

(From a Reuter Correspondent)

NEW YORK. Commercial airliners flying the international trade routes of the Northern Hemisphere this v/inter will be seeking new information on jet streams, the “rivers of air” in the upper troposphere which circle the globe in an easterly direction at altitudes between 18,000 feet and 45,000 feet.

The jet streams may be the trade winds of the future, when highaltitude jet-powered aircraft become the mainstays of long-range air transport.

Present-day piston-powered, propeller-driven aircraft occasionally “catch a ride” on the jet stream. But since they cannot operate above 25,000 feet, they cannot take full advantage of these high velocity currents on east-bound flights. Airliners of the future, such as the De Havilland Comet IV, the Boeing 707 and the Douglas DC-8, will operate normally at 40,000 feet or higher, and will be able to take full advantage of the growing fund of knowledge about jet stream navigation.

The winds, first discovered by American bomber pilots raiding Japan in 1944, travel at speeds varying from 90 to over 200 miles an hour. One jet stream was measured as reaching for a short time 357 miles an hour. The rapid distribution round the world of radioactive particles from atomic and nuclear explosions is believed to be due in part to the jet stream. The Japanese used the Pacific jet stream late in World War II to float incendiary balloons across the ocean to the northwest United States.

Today, weather balloons launched by ground weather stations in many parts of the world provide new data on the flow of the jet stream. But the principal research into the subject is that conducted by the crews of commercial aircraft, seeking to cut their flight time by riding the stream on east-bound flights, and avoiding it in west-bound flights. The principal airlines of the world have encouraged jet stream research in the interests of faster and more economical flying. In some cases, meteorologists employed by the airlines have gone further in jet stream research than have their colleagues who are employed by governments, although th'' possible military applications of the jet stream have been coming to the fore with the advent of high-altitude jet bombers seeking ever greater speed and range. In the days of bailing ships, captains often steered well off the direct route in crossing the Atlantic to pick up favourable winds. So it is with airline pilots today. Following carefully-plotted “least time tracks” individual flight paths which take advantage of prevailing air currents—they save minutes and even hours in a crossing, in spite of having flown sometimes as much as 700 miles off the direct route.

The jet stream is known to be stronger in winter than in summer. It starts building up in mid-October and reaches its peak in January. During the winter months, economy of operation becomes increasingly important to international airlines, for it is during those months that paying traffic drops to its lowest level for the year. “Jet Stream Put to Work” One of the pioneers in jet stream research has been Pan American World Airways, which operates commercial flights over most of the world, and notably over the Pacific and Atlantic oceans. Pan American claims to have been the first airline to put the jet stream to work for commercial aviation in everyday operations, with regular “jet stream” briefings for members of crews on international flights. For the last four years, aircraft belonging to this airline, riding winter air currents which permit them to fly non-stop nearly 4000 miles from Tokyo to Honolulu, have saved seven hours on the normal 18-hour flight time. Using new knowledge of jet stream navigation, Pan American pilots have lowered the commercial trans-Atlantic records five times this year on. west-bound flights. In January, the London to New York record was set at 11 hours 35 minutes. In succeeding months, the minutes were pared to the existing record of 11 hours 18 minutes. One day in March of this year, navigating to avoid the east-bound jet stream, one of the airline’s DC-7B’s flew from Paris to New York in 11 hours 18 minutes, breaking a four-year-old record by over an hour and a half.

The first people to become aware of jet stream conditions over the Atlantic were the pilots who began higher-altitude flying with the advent of pressurised aircraft in 1945.

In November 1949, a Pan American aeroplane commanded by Captain Charles Titus, encountered one of the strongest jet streams observed to this day. He flew his machine from New York to London in 8 hours 55 minutes, a timing which remained unchalleged for six years.

In 1955, three new records were set up on the same day, October 5. Riding the jet stream 80 per cent, of the way, three aircraft set these records: New York to London in 8 hours 52 minutes: New York to Paris in 9 hours 20 minutes; New York to Prestwick, Scotland, in 8 hours 10 minutes.

One of the leading authorities on jet stream navigation is Mr E. Brewster Buxton, chief meteorologist for the Pan American World Airways. He said: “For each of our trans-Atlantic flights, our dispatchers plot what is called a least-time-track, taking advantage of jet stream winds. The direct route between New York and London, called the Great Circle Track, is 3475 statute miles, but these tracks may curve north or south as much as 700 miles off the Great Circle. Least-time-track charts last year showed an average saving of 45 minutes between London and New York, and 30 minutes between New York and London. Flying in the jet stream is smoother, too—no clouds, and no bumps.” For information about the position, location and intensity of the jet stream, trans-Atlantic pilots draw on reports from Government weather units in London, Paris. New York, Keflavik, Shannon and Gander, as well as from over 100 ship and shore upper-air sounding stations.

Even with all these aids, however, jet stream forecasts are approximate, so crews still have to rely a great deal on their own skill to “sniff out” their actual position. One pilot has described the hunt as “like stalking something in a submarine.” Already the use of the jet stream is saving an impressive sum of money in operating costs for airlines, and hours of time for air passengers. By 1958-59 airstream flying may come into its own.