Plane Noisy

Plane Noisy
I always have two really anxious moments on every flight: landing and take-off. Well, more specifically it's that point when the landing gear is half way in, half way out and there's this dreadful noise of rushing air, making it seem like the belly of the fuselage has been ripped open and we're about to spiral into the ground. Speaking of the ground, down there on the surface it's noisy too, a fact I can attest to, living in line with a busy runway at the exact point where approaching aircraft lower their undercarriages.

So what are aerospace engineers doing to combat all these landing gear sound effects?

Well at NASA, they're colouring in.

Admittedly the colours are being added in a high-tech manner. In a series of tests conducted at NASA's Ames Research Center, the sounds generated by aircraft landing gear have been depicted as coloured graphics on a computer screen. The data gathered will provide critical visual information to aircraft designers concerned about possible enforcement of stricter aircraft noise rules. The images are enabling the NASA boffins to pinpoint loud and preventable aircraft flight sounds more easily than in the past, raising the prospect of quieter take-off and landings.

Airframe karaoke
"Some airports are imposing night-time curfews on noisy take-offs and landings, encouraging aircraft manufacturers to make quieter planes," said Paul Soderman, leader of the Ames aero-acoustics group. "If U.S. airplane makers can't meet the new noise rules, those manufacturers may well have difficulty selling their aircraft, both domestically and in foreign markets," he speculated.

The research at Ames is pre-empting the fact that lower aircraft noise limits might also be issued by the International Civil Aviation Organisation, which makes aircraft noise rules for the rest of the world.

Using an array of 70 computer-connected microphones inside the wall of a wind tunnel, the NASA engineers produced vivid images of the landing gear wind sounds that normally occur during aircraft take-off and landings. The microphone array minimizes the sound spawned by the wind tunnel itself, so that only noise from the landing gear is depicted. Using quarter-scale mock-ups of the aircraft parts, noise sources as small as 6 mm can be identified. At full-scale, these bumps and projections would be 24 mm across, or about an inch. The researchers found they could reduce noise significantly as they removed various combinations of landing gear parts from the test model.

"Now that we can easily see the causes of the annoying 'whooshing' wind noises that come from airliner landing gear, we can take steps to analyse and eventually reduce the noise significantly," continued Soderman. On approach, airframe parts, including landing gear, flaps and slats, create almost as much racket as the engines.

Air fair
"We are pleased to see a lot of detail in the sound pictures," Soderman says, but he adds a cautionary note on how far the results can be taken.

"Removing pieces, or altering part shapes, is not as easy as it sounds because many of the changes would greatly affect how the landing gear and plane operate. Landing gear slows an airplane as it comes in for a landing, and if we reduce the drag too much, the plane would be traveling faster than it should as it approaches the runway."

Soderman expects that the conclusions from this round of testing will enable aeronautical engineers to decide how to create air drag for slowing the plane without causing excess noise.

"Preliminary data analysis indicates that a faired landing gear generates considerably less noise than an unmodified landing gear….Though full fairings may not be commercially practical, the data represent a probable lower limit of landing gear noise." (A fairing is a streamlined shield for reducing drag caused by wind flowing around irregular surfaces.)

The next phase of the program comes in June 2001. Then, engineers plan to attach the model landing gear a model wing and to conduct more tests. These are slated to take place in a much larger wind tunnel. The group will measure airframe fly-over noise and surface wing pressures with and without the landing gear extended during simulated runway approaches. Most importantly, they will also evaluate noise control devices.

And that might save people like me our disturbing in-flight visions.

Home | Top Deals | Airline Safety | International Travel | Future Air Travel
© 2001 airlinelounge.com | Contact