O'HARE — Planes landed and took off as promised 57 percent of the time during the first eight weeks 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 summer storms often prompted air traffic controllers and airport officials to divert planes from the runways that were supposed to keep designated areas quieter.
About two months into the six-month test period, 67 percent of planes used the primary runway configuration designed to limit landing and takeoff noise in a single week. That high-water mark was achieved the week of Aug. 21-27, according to the data.
But the previous week — Aug. 14-21 — only 35 percent of planes used the primary runway configuration "due to weather conditions across the country," according to city aviation officials.
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.
The O'Hare Noise Compatibility Commission is set to meet Friday morning to review the results of the pilot for the first time.
Because storms can play havoc with the 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.
Through the first eight weeks of the program, planes used that secondary runway configuration 16 percent of the time.
That means about 100 planes that landed and took off at O'Hare nightly followed the rotation 73 percent of the time July 6-Aug. 27, according to the data.
The voluntary restrictions on nighttime operations at O'Hare, known as Fly Quiet, encourage pilots and air traffic controllers to fly over expressways, industrial areas and forest preserves to reduce the noise over residential areas from 10 p.m.-7 a.m.
From July 6 -Aug. 27, 74 percent of planes followed those guidelines, including those planes that took off and landed while the rotation was in effect, typically from 11 p.m.-5:40 p.m.
The schedule of which runways are in use at night is available online so people will know what to expect, officials said.
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 complaint hotline with more than 500,000 complaints since the beginning of the year.
While the pilot rotation plan has meant less noise at night for some Chicagoans on some nights, it has meant more noise for those living in northwest suburbs like 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.
Chicago Aviation Commissioner Ginger Evans has touted the rotation as a "big breakthrough" in city efforts to reduce the jet noise that prompted more than 4 million complaints in 2015.
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.
Members of the coalition have credited the rotation for giving its members "relief for the first time in almost three years."
But they have also criticized the rotation as offering only temporary relief, since it relies on a runway scheduled to be demolished.
City aviation officials have said noise will be more equally distributed around the airport once the expansion is complete, which is expected in 2020.
After the pilot program ends Dec. 25, the O'Hare Noise Compatibility Commission and city aviation officials will decide whether to make the rotation permanent.
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