O'HARE — Planes landed and took off as promised about half the time during the first three months of a test to rotate the O'Hare Airport runways used at night to give Northwest Side residents some relief from jet noise.
Data released by the Chicago Aviation Department shows that storms, construction projects, high demand and required safety inspections often prompted air traffic controllers and airport officials to divert planes from the runways that were supposed to keep designated areas quieter.
Halfway through the six-month test period, about 55 percent of planes used the primary runway configuration designed to limit landing and takeoff noise in a single week on average. About 100 planes take off and land between 10 p.m. and 7 a.m. daily.
Because storms can play havoc with winds at O'Hare — forcing planes to change directions so they can land safely against the wind — planes can be directed to use a second set of runways as part of the rotation. Planes used that alternate configuration about 18 percent of the time.
The runway rotation is designed to give residents near the airport a break from the noise that some contend has made it impossible to get an uninterrupted night of sleep since an east-west runway opened in 2013.
If the number of complaints filed by Chicago residents is an indication, the effort seems to be working.
Objections to nighttime noise dropped 27 percent from July to August, the first full month of the rotation plan.
In addition, the number of complaints filed about nighttime noise in August was 47 percent lower than it was a year ago.
John Kane, a member of the coalition, asked the the O'Hare Noise Compatibility Commission Friday to extend the rotation after its scheduled end Dec. 25 because of its success thus far.
"It has certainly tempered some of the anger at jet noise," Kane said. "It has had a positive impact, and quieted the night skies."
Commission chairwoman Arlene Juracek said extending the rotation was "certainly worth discussing."
"We don't want to lose any of its benefits," Juracek said.
The voluntary restrictions on nighttime operations at O'Hare, known as "fly quiet," encourage pilots and air traffic controllers to use designated runways — published in advance so those who live under the flight path know what to expect — to reduce noise over residential areas.
On most nights, the rotation was in effect from 10:50 p.m.-5:41 a.m., according to data complied by the Aviation Department.
The effect of the rotation plan has been to shift some jet noise back to the way it was before October 2013, when the then new east-west runway opened as part of the $8.7 billion O'Hare Modernization Program, sending hundreds of flights over neighborhoods such as North Park, Jefferson Park, Edgebrook, Edison Park and Norwood Park that previously experienced little or no jet noise.
The change incensed many residents, who have inundated elected officials and the city's official hotline with more than 1 million complaints since the beginning of the year.
While the pilot rotation plan has yielded less noise at night for some Chicagoans on some nights, it has created more noise for those living in northwest suburbs like Park Ridge, Des Plaines and Palatine.
In addition to the percentage of planes following the rotation, the success of the test also will be judged by the results of online surveys that ask residents whether the plan is making a difference in their quality of life, officials said.
The rotation includes a diagonal runway on the west side of the airport until 2019, when it is slated to be demolished to make way for the sixth and final east-west runway.
City officials have steadfastly rejected pleas from members of the Fair Allocation in Runways Coalition to keep four diagonal runways in service at O'Hare as the only way to reduce jet noise over the Northwest Side.
Two diagonal runways are slated to remain in service at O'Hare.
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