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Discussion of the noise problem around O'Hare International Airport has mostly centered not on the aircraft itself but on scheduling, flight paths, runway direction and sound insulation for homes and businesses.
But a big factor in jet noise is what's inside the plane, such as the engine and the exhaust system. Recent breakthroughs in engine design and other changes in the next generation of commercial jets promise to dramatically reduce the roar that disrupts classrooms and North Side and suburban barbecues. The question is when there will be enough new parts and planes to make a difference.
The average age of a U.S. commercial aircraft is more than 11 years old, though components can be modernized over the life of the plane, like the parts in a car. It takes time for airlines to overhaul their fleets, so it will be a few years before noise-rattled neighbors can notice what they're no longer hearing.
"It's not a total cure, but they have the potential to make a significant amount of difference," Mount Prospect Mayor Arlene Juracek, chairwoman of the O'Hare Noise Compatibility Commission, said of the new designs. "There are a lot of fascinating ideas being worked out."
Plane manufacturers and airlines have a big financial incentive to reduce the amount of fuel they use and fortunately, for people who live around airports, many of the same innovations that lower fuel consumption also cut noise and pollution emissions.
"Fuel efficiency goes hand in hand with the quieter aircraft," said Leslie Scott, spokeswoman for American Airlines, which has been retiring its MD-80s and bringing in quieter Boeing 787-8 and 787-9 Dreamliners.
"The single most impactful way we can mitigate noise is by investing in new aircraft that are quieter and more fuel efficient," agreed Charles Hobart, spokesman for United Airlines.
With a program called Continuous Lower Energy, Emissions and Noise (CLEEN), started in 2000 and continued as CLEEN II last year, the Federal Aviation Administration has been working with manufacturers like GE, Honeywell and Boeing to develop cleaner, more fuel-efficient and quieter technology. The changes include lighter materials, such as swapping out metal alloys for ceramics, alternative fuels and changes in how engines handle air flow.
One recent major innovation in reducing jet noise is the geared turbofan engine, produced by Pratt & Whitney and already going into planes in India and Europe.
The difference between the new GTF engine and a conventional engine is that much more air moves around the engine instead of through its center, said Greg Gernhardt, commercial engines programs president at Pratt & Whitney.
In a fighter jet, for example, all the air goes through the core of the engine, producing a mighty roar, Gernhardt said. Commercial aircraft have been developed over the years to have more air go around the engine — evolving from the JT8D engine of the 1960s that was "quite a loud beast," said Richard Aboulafia, an analyst with Teal Group, a Washington, D.C.-based aviation consulting firm.
A modern single-aisle aircraft like the 737, has a higher "bypass," and about five times more air goes around the engine than through the core, Gernhardt said. With the geared turbofan engine, 12 times the amount of air goes around the engine as through it, Gernhardt said. The noise difference if you're in a Wood Dale backyard is like the contrast between a lawnmower and an electric razor, Gernhardt said.
"The engine is still providing plenty of thrust, but you don't have to use as much fuel to move it, and you don't have to hear that noise," Aboulafia said.
Pratt & Whitney has sold 7,100 GTF engines for a variety of aircraft, including 737s, Airbus 320s and Embraer 190s and 195 E2s. The process of getting engines into planes takes time — worldwide, about 1,200 planes will get the engines in the next four years.
Another new engine is the CFM LEAP-1A, created through a joint venture between GE and Safran, a French company. This high bypass engine, which will go into Airbus 320neo planes, promises double-digit reductions in fuel consumption and CO2 emissions as well as cuts in noise.
Boeing has tested an engine nozzle made of a ceramic matrix composite, designed to reduce noise, weight and fuel consumption. The Chicago-based company said it also is working with airlines and operators to develop new takeoff and landing procedures to cut community noise, such as slightly higher descent angles.
Rolls-Royce has been using acoustic liners in jet engine housing to cut noise, according to the company.
Whether the reduction in noise will significantly reduce complaints depends on a number of factors, including the number of jets, flight paths and the sensitivity of residents. Improvements in jet technology over the decades already has made a difference. In 1979, the O'Hare "noise contour" — that is, the area affected by airport noise, was 89.3 square miles, according to the O'Hare Noise Compatibility Commission. Phasing out noisy older jets helped reduce the contour to 21.2 square miles by 2002. By the time of the full O'Hare expansion build-out in 2020, it's expected to be 17.6 square miles.
But noise complaints shot up dramatically in recent years after the city began shifting traffic from older diagonal runways to new parallel east-west runways, which concentrate more traffic over the North Side and the western suburbs. Some area residents who hadn't been affected by jet noise before began to hear it.
The city got more than 4 million noise complaints in 2015, and Fair Allocation in Runways or FAiR, a group that represents city and suburban residents, is concerned that the planned closing of the diagonal runway 14R/32L in late 2018 will make the situation worse.
FAiR member Al Rapp of Park Ridge, said it's good that newer planes will be less noisy than planes flying around now. But he said O'Hare is planning for greater future capacity, which Rapp fears could cancel out airplane design improvements.
"The noise contour will go up instead of down because the capacity will go up, so we'll have more planes at closer intervals," Rapp said.
Original article can be found here: http://www.chicagotribune.com