Northern Hills Homeowner's Association

Denver Opposes Hush Kitted Planes

Nov 22, 2000

DIA to reroute noisiest jets
By Jeffrey Leib
Denver Post Staff Writer

Nov. 22, 2000 - The noisiest jets departing from Denver International Airport will begin flying on paths that take them away from the most densely
populated areas of the city as part of a 90-day test.

Airlines, including United and Frontier, and city aviation officials agreed to conduct the test early next year because of the sharp increase in
aircraft noise violations west of DIA.

Mike McKee, DIA's noise abatement officer, said a preliminary review of aircraft noise data for the airport's fifth year of operation - which ended
Feb. 29 - showed the number of noise violations nearly doubled from the previous year.

Ironically, airport officials attribute the increase in noise violations to planes outfitted with engine devices called "hush kits" that were supposed to muffle noise.

By government fiat, all airlines had to add hush kits to their oldest and noisiest planes by Jan. 1 of this year to meet a so-called Stage 3 noise
standard.

Before getting the engine mufflers, older, noisier aircraft had to fly either far to the north or south out of DIA before they turned toward western destinations.

After adding hush kits to their planes, airlines were relieved of any restrictions on where they could fly the jets, McKee said, even though the
reduction in noise was minimal for hush-kitted aircraft.

Next year's noise reduction test, which could begin as early as Jan. 1, calls for hush-kitted aircraft to follow the far north and far south
departure routes once again. To the north, it takes planes as far as Laramie before they turn toward destinations such as San Francisco.

"We obviously hope this test is successful in reducing the number of (noise) violations that occur to the west" of DIA, McKee said.

If the airport doesn't reduce aircraft noise especially at key monitoring points near DIA, it faces fines for violating an agreement reached with Adams County that called for a restriction of jet noise.

In October 1999, a judge assessed more than $4 million in "noise mitigation penalties" after Adams County said noise levels were elevated in DIA's first year of operation. DIA is appealing that ruling.

Norman Lederman, who lives in the mountains between Boulder and Nederland, said that as hushkitted planes were free to follow more direct westbound flight paths, there was a noticeable increase in aircraft noise over his community and the nearby Indian Peaks wilderness area.

Lederman ought to know. He's an audio engineer who set up equipment outside his home to monitor jet noise overhead.

He said planes that were brought under the government's Stage 3 noise standard with hush kits were typically 10 decibels louder than "true" Stage 3 planes - those that carriers bought from manufacturers with quieter
engines.

That extra 10 decibels made the hush-kitted Stage 3 planes twice as loud, said Lederman, who heads the aviation noise pollution committee of his
homeowners' association.

Lederman welcomed the airlines' voluntary agreement to once again route noisier jets far to the north or south before turning toward western
destinations.

"It's a positive step, an acknowledgement that these hush-kitted older aircraft" do not meet the noise standard of true Stage 3 planes, he said.

Frontier chief pilot Hank Appleby said his carrier is joining next year's test with its hush-kitted jets because it's good for the community.

- GRAPHIC: Noise test plan
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