City, Wings to test quieter plane engine

Posted: Friday, April 04, 2003

The city and flightseeing operator Wings of Alaska think a turbine-engine Otter would be much quieter than the floatplane engines now in use on Juneau's downtown waterfront. They plan to test their hypothesis next month to be sure.

Juneau Assembly members last week agreed to spend $10,000 to bring a turbine engine Otter and a flightseeing noise consultant to town. The city plans to test the Ketchikan plane against the reciprocating-engine Otters that Wings currently uses, said city Lands Manager Steve Gilbertson.

Previous work by city noise consultant Paul Dunholter showed that a Cessna Caravan with a turbine engine was about 10 decibels quieter than a standard Otter. Decibels are logarithmic, which means a 10-decibel reduction is significantly quieter, Gilbertson said.

Dunholter's study also said a turbine engine is less irritating because the pitch is lower and the duration of the sound is reduced.

Bob Jacobsen, president of Wings of Alaska, said his company would be willing to retrofit two Otters this winter, with financial help from the city, if people think it would make a difference.

"It's not my opinion that counts, it's the residents that are affected and the policymakers," he said. "Turbine engines are quieter than reciprocating engines; however, it's really up to those affected if the improvement will be to their liking."

The new engines are much more expensive. A rebuilt reciprocating engine recently cost Wings $28,000, while the cost to retrofit one Otter with a turbine engine could run $510,000. The cost is higher, in part, because a major rebuild of the front of the aircraft is required, according to the city. Wings of Alaska has five Otters.

Assembly members set aside $500,000 in cruise ship passenger fees last year for quiet technology and heliports as a way to reduce flightseeing noise. Deputy Mayor Ken Koelsch said people will need to buy into the conversion to make it work, he said.

"This is exactly what the money is for," he said, referring to the passenger fees. "Hopefully, it shows it will reduce noise."

Assembly member Jim Powell also supported the test, but said he is concerned people might forget about the change in a couple of years.

"My main concern is people's institutional memories, that people's memories would start to fade about the improvement," he said.

The city could provide a low-interest loan to Wings if officials decided to proceed with the new engines after the test, Gilbertson said. Such a move wouldn't be unprecedented. The city offered private developers zero-interest loans for 20 percent of the cost of a housing project during a housing shortage in 1983, he said. The developer had to acquire 80 percent of the financing through conventional means.

The noise tests may be scheduled for the third week of May. Assembly members asked city staff to alert the public ahead of time so people can judge the difference for themselves.

Joanna Markell can be reached at

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