Science: Lights for Landing

When foul weather wipes out familiar landmarks, airline pilots have the I.L.S. (Instrument Landing System) glide path to lead them in a gradual descent to the runway. At many airports they also have G.C.A. (Ground Controlled Approach) operators to monitor every move. But before a plane drops below the ceiling and visibility minimums permitted by the C.A.A., the pilot must be able to see the ground. It is this quick shift from “instrument” to “contact” flying that separates the men from the boys. Last week, at Newark Airport, the Air Line Pilots Association demonstrated a new approach light system designed to make life easier for the man in the final moments of flight.

The A.L.P.A. system eliminates the twin rows of lights, now in use, which sometimes lead pilots to mistake one side of the approach lane for the other. It substitutes a single row of horizontal light bars leading to the runway centerline. Each light bar is long enough to serve as an artificial horizon, telling the pilot if his plane is on even keel. At a distance of 1,000 feet from the runway, five bars abreast make an extra-wide horizon.

Another refinement of the A.L.P.A. system is a string of condenser-discharge lights* down the center of the approach lane. They flash with 600-million candlepower, a brilliance that makes the bright white bars seem orange by contrast. The flashes are arranged in sequence, flicking in toward the runway and marking the landing direction like a stream of tracer bullets. And the pilot can easily locate the runway threshold, which is outlined with high-intensity green lights and a check point of five red bars.

Airline captains who have never been satisfied with any other approach lights are loudly enthusiastic over the A.L.P.A.’s contribution. It is their system, designed to their own specifications, and they hope to see it a standard at all airports.

* Similar to the stroboscopic lights used in high-peed photography.