Flying the Weather

As even airmen admit, the greatest hazard to safe, speedy flying is the weather-beaten air. Item: fortnight ago the pilot of a fogbound American Airlines flagship piled into a California mountain peak, killing all 27 people aboard--the worst commercial air disaster on record. This accident would perhaps never have happened had all the war-born safety devices been in general use.

But as far as U.S. commercial airlines are concerned, there has been no basic change in air traffic control, airway marking, or instrument landing equipment in 15 years--a period that has seen an enormous increase in scheduled flights and the advent of 300-mile-an-hour transports.

VHP. Now, belatedly, the Civil Aeronautics Administration has started a limited program of improvements. First step is the installation of Very High Frequency radio ranges (VHF) on the airways. Their ultrashort waves can punch through most electrical disturbances, keep pilots from getting lost and slamming into mountains. Like television, VHF transmission is limited to the line of sight, necessitating a great many stations. But within two years CAA intends to blanket the country with VHF.

Another forward step is the improved blind landing equipment which CAA is now installing at 100 commercial airports. At present, pilots bring their planes down out of the murk with the help of a simple four-directional radio range, radio position markers and the plane's own instruments.

The new CAA system, far more elaborate, will do much more. It will guide the pilot down a glide path directly to the runway. At intervals, radio markers will tell him his position upon it. The new system will not only be safer but faster, reducing the tedious and dangerous "stacking up" which often clogs busy airports.

Loran. When air lines cross the oceans, they will be guided by war-born loran (LOng RAnge Navigation), a whole new system of navigation which does not depend on celestial observations or hit-or-miss dead reckoning. The U.S. Coast Guard already operates 57 loran stations on the shores and islands of the Atlantic and Pacific. Each has an effective range of 600 to 800 miles by day, and up to 1,400 miles by night. A worldwide network of 70 stations is in the cards.

Loran shore stations always work in pairs: the "master" and the "slave" (see diagram). Both operate on the same frequency and both broadcast the same radio "pulse signals"--short bursts of radio energy transmitted at regular intervals. The pulse from the master station appears as a "pip" on the "scope" of the plane's loran receiver. It also sets off a second pulse from the slave station, which is received as a second pip. The pulses arrive at slightly different times, since they have traveled different distances.

The key to loran is the measurement of this time lag, which the receiver does automatically in micro-seconds (millionths of a second). For each time lag, a special chart shows a "line of position." The plane's navigator knows at once that he is somewhere on this line. Then he tunes in a second pair of master-and-slave stations operating on a different frequency, and gets a second line of position. His location on the chart is the point where the two lines intersect. A skilled operator can complete the whole problem in less than six minutes.

Radar. Some day radar will supply the key to all-weather flying, but not immediately. One reason: airline safety standards demand long service testing. Another: CAA has been remarkably slow in accepting military radar devices.

Eventually, pilots hope, an integrated radar system will give the position of every plane within 80 miles of an airport, and enable every pilot to see his own position in relation to the landing field. By then, accidents such as last fortnight's California crash will be due only to mechanical failure or human carelessness.

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