Sky-high costs that fly in the face of current economic logic are forcing some US broadcasting stations to take a hard new look at the use of one of the most sophisticated tools of their trade: helicopters.
The so-called ''eye in the sky'' machines, usually brightly painted and bearing the call letters and logotypes of the stations they serve, are heavily promoted as a means of keeping up with the news in even the most-distant corners of coverage areas. They are especially useful in covering spectacular fires, floods, stories at sea, and in reporting on rush-hour traffic conditions. One Dallas station recently used its helicopter to prepare a series of reports on toxic waste disposal at a site that was hidden at ground level by a high hedge.
As recently as last September, according to Flying magazine, more than 70 television stations owned or leased helicopters. The number of radio stations that use them may be unknown, but normally when one station in a market begins using a helicopter, others feel compelled to follow suit.
But, whether owned or leased, helicopters are extremely expensive to operate -- costing as much as $400,000 a year.
Earlier this month Boston's WEEI became the latest radio station to announce it had given up the use of a helicopter. For seven years the ''all news'' station had sent a reporter-pilot aloft in a leased machine to report on rush-hour commuter traffic. But of late, a spokeswoman said, fuel bills alone were costing the station $15,000 a month.
The station now broadcasts traffic information gathered by the same reporter and spotters who operate from the skywalk of Boston's second-tallest building and by drivers of radio-equipped vehicles who monitor the roads each workday. ''It's a lot less expensive this way,'' the spokeswoman said. But she added that the station management might reconsider the use of a helicopter ''if it became more affordable.''
WEEI soon could be joined by other Boston stations, according to some sources in the industry. And in other parts of the country stations have switched to the use of light, fixed-wing airplanes, which can be as much as six times cheaper to operate, to enchance their news or traffic coverage.
Says Ernie Schultz, executive vice-president of the Radio-Television News Directors Association in Washington, D.C.: ''I think there is some retrenchment. A lot of helicopters were obtained for competitive reasons rather than out of real need.''
WMAL Radio, a leading station in Washington, gave up helicopters in late 1980 and switched to fixed-wing aircraft for its traffic reports. Says news director Len Deibert, ''The cost was prohibitive, and, from a maintenance standpoint, they were down more'' than the fixed-wing plane is.
Veteran WMAL traffic reporter ''Captain Dan'' Rosenson, who has flown both types of aircraft, adds: ''There's no question that helicopter service, like everything else in this country, is going out of sight. But, generally speaking, the top stations in the country have never wavered'' in their commitment to report on traffic conditions. ''If radio stations could do something else to fill those eight or nine minutes (of rush-hour reports), trust me, that's what they'd do. Because you're talking about thousands of dollars of revenue.''
''Three or four years ago,'' according to Jack Swanson of KGO Radio in San Francisco, which uses both a helicopter and a plane, ''you'd go to a news directors convention and the helicopter salesmen would have a $300,000 jet model sitting right there on the convention floor. Now they're putting a $150,000 two-seater piston model on the floor because they know stations aren't going to go for the extra expense anymore.''
No so, says Ray Ingham of Bell Helicopter of Fort Worth, Texas - or, at least , not exactly so. He contends the smaller craft have begun making such appearances because of the development of smaller broadcasting equipment that will fit into them.
Bell, which claims a 90 percent share of the radio-TV sales market, sees a potential ''for at least 200 more of the top-level stations that have not come on line yet,'' Mr. Ingham says. But he concedes that ''demand has flattened out over what it was two to three years ago.''
Still, in television particularly, the appeal seems almost irresistible. WFSB-TV in Hartford, Conn., would only give up its helicopter ''reluctantly -- if the recession deepened and I had to cut somewhere,'' says news director Dick Ahles.
But their appeal may be best illustrated by WFAA-TV in Dallas, which uses an identical $500,000 jet helicopter after its first one crashed in 1980, killing three people. Says news director Marty Haag: ''I can understand why some stations would ground them; the cost is considerable. But we just figure that there are too many opportunities to use them for us to be without.''