Flight International Online news 11:30GMT: A consortium consisting of Boeing, General Electric, Goodrich and NASA today said tests into aircraft noise reduction have been successful.
The August tests completed the second phase of the Quiet Technology Demonstrator (QTD 2), a program that uses an All Nippon Airways Boeing 777-300ER to determine the usefulness of several concepts, including nacelle design and sound-absorbing liner.
“The flight-test program provided the opportunity for each company to validate key technologies for incorporation into its own current and future products. NASA joined the effort to acquire data to support its advances in propulsion aeroacoustics, landing gear noise, and computational fluid dynamics research,” says Boeing in a statement.
As part of QTD 2 the General Electric GE90-115B-powered 777-300ER was fitted with eight different noise-reduction engine inlet and exhaust combinations on the right wing, and the baseline production engine on the left wing. “Fan and engine-core chevron exhaust configurations achieved as much as a two-decibel improvement - a significant community noise reduction,” says Boeing.
“Because jet noise is generated by the jet wake - extending nearly 50ft (15m) behind the engine - any reduction is considered a significant achievement. In addition, the low-frequency rumble heard in the aft cabin by passengers during cruise was reduced by up to four to six decibels,” the manufacturer adds.
Also successfully tested, says Boeing, was a sound-absorbing liner on the engine inlet. A new ‘seamless’ construction that keeps sound waves from bouncing off joints increased the effective treated area by 78% over the current version, without increasing the nacelle size. “This new acoustic liner resulted in fan tones heard in the front of the aircraft being reduced by up to 15 decibels, making this noise inaudible above other ambient sounds,” says the manufacturer.
“This is exactly what we wanted to achieve,” notes Boeing VP of 787 development Walt Gillette. “This makes the new 787 better for the people who will be inside the airplane and better for the people who live in the communities around airports.”
“Through these sound enhancements, we will be able to reduce the sidewall acoustical insulation throughout the cabin by several hundred pounds, improving the operating costs for our customers,” adds Gillette.
DARREN SHANNON / WASHINGTON
Source: Flight International
