Noise over Jet Noise

U.S. airlines are all set to take off into the jet age when Pan American World Airways begins flights to Europe around Nov. 1 with Boeing's 707, and American Airlines starts domestic jet service early next year. But last week the Port of New York Authority, operator of New York International Airport, the world's key international terminal (accounting for 60% of all air traffic bound to and from the U.S.) blew a warning whistle.

It raised grave doubts whether it will permit the 707 to operate, except under such restrictions that would make the flights lose money. The official reason for the Port Authority's stand: jet noise.

Idlewild stands alone in the U.S. in objecting to jets. Airports in Chicago, Los Angeles. Miami. Boston. Denver, Wichita, Oklahoma City and also Mexico City, Caracas and Vancouver, B.C. welcome and actively solicit jetliner test flights, figuring that an airport that cannot or will not take jets might as well go back to cow pasture.

Fractured Decibels. Plane builders themselves long ago recognized the noise problem, went to work developing suppressors that would cut the roar and whine of pure jet engines without cutting engine efficiency too much. Last week Boeing announced that it had licked the problem. It said that its suppressor had cut jet noise below the level promised purchasers of the 707, making it slightly less noisy than a Super Constellation. The trick was done by breaking up the jet stream and funneling it through 21 narrow after tubes instead of one big tube. "The big, doughnut-shaped exhaust roar," said a Boeing engineer, "was broken down into 21 smaller, bagel-sized noises." The loss in efficiency: only 2% loss in thrust (v. up to 20% in earlier supressor devices), plus a 2% increase in fuel use.

Even the highly critical Port Authority admitted that the suppressors have reduced jet noise at the normal measuring distance to 102 decibels, about the level of a piston-engine airliner. But it has also thrown a new factor into the dispute; the Authority argued that the results of tests it had made showed that the jet noise contained a high-pitched whine that made it much more objectionable to listeners than a piston-engine plane roar of a much higher decibel reading. But the Authority's own aviation-development specialist, Herbert O. Fisher, apparently disagreed. He joined with outside technicians in a report calling the suppressor a success, likely to make the 707 appreciably less objectionable to listeners than large piston planes.

Scared Silly. As the pressure built up, Idlewild gave grudging ground at week's end. It granted a 30-day extension to Pan Am to continue nonpassenger 707 flight tests between New York and Puerto Rico, allowing night flights and lifting the plane's weight restrictions from 190,000 Ibs. to the fully loaded capacity of 247,000 Ibs. But planes will still be required to follow strict flight and climb patterns that minimize annoyance to householders, because the Authority, said one airman, is still "scared silly" by its lawyers' warnings of possible householders' damage suits.*

* Despite the talk about airplane noises, few property owners ever bother to take legal action, and fewer still win. The U.S. Air Force, for example, has been named in 34 suits about aircraft noise. Although its planes operate without suppressors, only three suits were lost; only one of those involved pure jets.

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