The transportation staff of the Metropolitan Washington Council of Governments suggested yesterday four alternative flight paths to distribute more equitably the noise of airplanes flying up the Potomac River from National Airport.
The proposals were sought by the council board months ago as part of its year-old efforts to find a way to make the Montgomery County community of Cabin John Happier without making other communities angry.
Planes taking off upriver from National fly with reduced power to Cabin John -- about 10 miles northwest of the runway -- then turn toward their destinations and apply full power. The process is noisy. The residents of Cabin John, a placid, residential community wedged inside the beltway on the north bank of the Potomac, say they think it's unfair for them to get the 16 takeoffs per hour that National generates.
Last August, the Federal Aviation Administration tested an alternative takeoff pattern for southbound, downriver flight departures.
The agency said it is willing to test one of the council-proposed, northbound alternatives this year, if the council will move quickly and tell it which one to test. The council has scheduled a public meeting March 26 to help it reach that decision.
The four alternatives proposed by the council staff yesterday:
Plans would make their final turns and reapply power at 7 miles or 10 miles or 13 miles in a predetermined sequence, thus scattering the impact of the engine noise. The seven-mile turn would come at about Brookmont, just beyond the District-Maryland line; the 13-mile turn would occur at Potomac; Cabin John would still get the 10-mile turn.
All westbound and southbound planes would turn at 10 miles; all eastbound and northbound planes would turn alternately at 7, 10 and 13 miles.
The third variation would eliminate the 13-mile turn and would have planes turn in a predetermined sequence at either 7 or 10 miles.
Westbound and southbound planes would turn at 10 miles only; eastbound and northbound planes would turn at 7 or 10 miles.
The proposal is a refinement of a 1977 FAA suggestion. The agency said then it could simply send airplanes in all directions as they left the end of the National runway and everybody would share the problem. Cabin John residents liked the idea, but other opposed it at one of more fractious council board meetings.
The council staff did some surveys last August during the FAA's southbound test, when planes were directed to fly 10 miles downriver to Accokeek before turning to their final destinations instead of the usual five miles -- just south of the Woodrow Wilson Bridge in the Mount Vernon district.
According to the telephone survey, the percentage of people in the Mt. Vernon district bothered by aircraft noise changed from 43 percent before the test to 35 percent during the test. It rose to 65 percent of the people in Accokeek were bothered before the test, 64 percent during the test, and 30 percent after the test. In Tantallon, on the Prince George's County side, there was little difference, according to the survey.