The Hated Slopeline

On a rainy afternoon last week, an Italian airliner approached New York City's International (Idlewild) Airport through a low overcast from which heavy rain was falling. Guided by instruments and radar, Captain Guglielmo Algarotti brought the airplane out of ragged clouds at 300 ft. altitude and tried to land on Runway 22. He missed it and circled back into the clouds.

Captain Algarotti circled for three-quarters of an hour, then was given permission to land on Runway 4. His first try was unsuccessful; so were the second and third. On his fourth approach, the control tower warned him that he was flying too low while still out over Jamaica Bay. He tried to pull up, but the airliner faltered (probably stalled) and plunged into one of the 2,000-ft. piers that carry the "slopeline" approach lights of Runway 4. Sixteen of the 22 passengers and all ten crew members were killed.--Authorities are still investigating the cause of the accident. One possibility is crew fatigue. The airliner had flown from, Rome (18 hours) without change of crew.

But the crash stirred up among pilots a resentment that has rankled for years.

Many of them blamed the slopeline approach lights. In the official instructions distributed to its pilots by American Airlines appears the following entry for Idlewild Airport: "Caution! Slopeline approach lights in operation on Runway 4 can be mistaken for runway." The same warning is given about the slopeline lights at Washington and Los Angeles. No matter what is decided about last week's crash, many pilots will believe that the Italian captain tried to land on the water between the piers.

Dashes & Jags. The slopeline consists of two lines of lights at the end of the runway, on sloping supports like saw teeth. When an airplane makes a correct approach, they blend into two continuous lines. If the approach is not correct, they look broken up into dashes or jags, telling the pilot what is wrong.

The slopeline system, good theoretically, has never won acceptance. Pilots say that when an airliner is descending through low-lying clouds, the lights that are meant to help them sometimes turn into enemies. The critical moment comes when the pilot, who has been staring at his instruments and listening to radio voices, catches a glimpse of the fogshrouded earth and transfers to visual flying. Often he has only five seconds to shift his attention, size up the situation and make his decision.

This is not enough time, say the pilots, for figuring out the dashes or jags of the slopeline system. Sometimes a pilot can see only one line of lights and he does not know which one. At the crowded instant of transfer, the angled lights play tricks with perspective. Pilots landing safely but in a trembling sweat have reported that they saw the lights as a ladder plunging toward the earth.

More dangerous is a thick-weather possibility: when the pilot mistakes the slope-line lights for the lights outlining the runway. Many pilots have had this illusion and have pulled up just before landing on water or broken ground. The Italian captain may have made this mistake and actually landed on the pier that carries the lights.

Ever since the first slopeline system was installed in 1949, both airline managements and the Air Line Pilots' Association have protested against it. Their basic objection is that any system with two lines of lights can look like an outlined runway in difficult weather. They prefer a single "centerline" of lights leading to the center of the runway.

Balls of Fire. The best system of all, according to many pilots, is the one at Newark Airport. Instead of two lines of lights, it has a single centerline of horizontal bars, which cannot possibly be mistaken for the runway. In thick weather stroboscopic lights ("balls of fire") flash briefly in sequence so that they look to the pilot like a stream of tracer bullets.

The CAA recognizes the failings of the slopeline system, and the centerline system is now its standard for civil airports. But, presumably because of lack of money, only eight U.S. airports have centerline lights. Only Newark has the balls of fire. A hopeful rumor at International Airport is that the slopeline lights of Runway 4 (now out of commission) will be replaced by the centerline system, perhaps including the balls of fire.

* For another view of the tragedy, see JUDGMENTS & PROPHECIES.

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