Science: Omnirange to Guide Them

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The time is coming when an airliner can fly through the air (stormy) with the greatest of ease and land on an airport (fogbound) as if the day were clear. Last week the Civil Aeronautics Authority was busily installing "omniranges": the key gadget of the new navigation system. Two hundred and seventy of them are already in place. By early next summer there will be over 400, blanketing nearly all the U.S.

Under the old system, airliners are led from airport to airport by radio ranges which sound an on-course signal in the pilot's ears only when the plane is in one of four narrow beams. Planes outside the beams get little help from the radio. Even when they stay on the beam, they have no way of telling how far they are from the station.

Another bad feature of the old-style ranges is that airliners have to fly directly from station to station. This causes traffic congestion. In bad weather a long-distance plane cannot strike off cross-country to avoid the neighborhood of a busy airport. If it does, it gets off the beam and may have to go through time-wasting maneuvers to get back on again.

Any Direction. The omniranges are changing all that. Operating at very high frequency, they are entirely free from static. They do not send out restricted beams but can tell any plane within their range (50 miles or more, depending on altitude) in what direction it is heading in relation to the station. The pilot need not listen to wearying dots and dashes in his headset. All he has to do if he wants to fly toward the omnirange is to tune to its frequency and then watch a needle on his instrument board. When the needle is ver tical, the plane is headed toward the station (see diagram).

Hitched to the omnirange is another pilot-comforter: the DME (Distance Measuring Equipment). If the pilot wants to know how far he is from a certain omnirange, he turns on a transmitter that sends out a coded signal. When this reaches the omnirange, a repeater answers like an echo. An automatic device on the plane measures the time between the signal and the echo. It turns this interval into the distance in miles and "displays" it on a dial. This gives the pilot a perfect "fix." He knows his direction and distance from the omnirange. Therefore he knows exactly where he is, though there may be three miles of clouds between him and the earth.

Any Course. The pilot of a fully equipped airliner will not even have to take such fixes. Another device, the course-line computer, will do the worrying for him. He merely selects (by setting a dial) the course he wants to follow within the territory of a certain omnirange. The gadgets do the rest, measuring continuously both distance and direction and digesting the information electronically. All the pilot has to do is watch the magic needle. As long as it is vertical, he is on his preset course. He can fly where he chooses, selecting the most direct route and avoiding traffic by never coming close to an airport until he nears his final destination.

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