Technology being tested on this Boeing 777 in Montana is
expected to find its way into 787s, due to enter service in
2008, and the 747 Advanced. (August 11, 2005)
Credit: James Wallace/Seattle Post-Intelligencer
Posted on 08/13/2005 2:43:03 PM PDT by Paleo Conservative
GLASGOW, Mont. -- At a remote airfield in northeastern Montana, where the quiet is usually broken only by the singing of Western meadowlarks, a Boeing 777-300ER jetliner made some symbolic noise of its own Wednesday.
But it was the lack of noise from the big plane that will help advance aviation.
The Boeing Co. and some of its partners, including NASA, are testing new methods and technology that can make commercial jetliners quieter when landing and taking off -- a growing concern at airports from Sea-Tac to Singapore and Paris.
Passengers also will benefit from the ongoing efforts as cabin noise will be significantly reduced.
Some of the technology being tested here will find its way onto the 787, which is due to enter airline service in 2008, as well as the 747 Advanced and even planes now in production.
Technology being tested on this Boeing 777 in Montana is
expected to find its way into 787s, due to enter service in
2008, and the 747 Advanced. (August 11, 2005)
Credit: James Wallace/Seattle Post-Intelligencer
Wednesday, with reporters watching and listening from the ground, as well as representatives from NASA, General Electric and Goodrich, a 777-300ER on loan from All Nippon Airways made several low-level passes over the airfield to demonstrate advanced noise-reduction concepts.
More than 600 ground-based microphones, acting like acoustic cameras, monitored the jetliner's noise as it flew overhead, and computers wired to the microphones immediately analyzed the data and verified that the modifications made the big jet less noisy.
"We are trying to make the 787 significantly quieter" than today's planes, said Eric Nesbitt, a noise engineer in Boeing's product development for commercial airplanes.
He helped develop the Boeing test program, known as "quiet technology demonstrator."
What's taking place here in Glasgow is a follow-up to noise testing done here in 2001.
The twin-engine 777-300ER has the world's biggest and most powerful jet engines, the GE90- 115B. They are certified for 115,000 pounds of thrust. On the test plane, the left engine is the standard GE90-115B. But the right engine is modified to include acoustics that make nearly 100 percent of the nacelle inlet inner surface sound-absorbent. The nacelle is the casing that wraps around a jet engine.
The noise that comes out the front of a jet engine, produced by the fan as well as the low-pressure booster that sends air through the core, causes a buzz-saw type of noise that can be heard by passengers in the front of the passenger cabin, often in first and business class. The new acoustic inlet liner significantly reduces that cabin noise.
Some of this noise also hits the ground on takeoff or landing, so the nacelle treatment also helps with ground noise.
"We need this to be production-ready in time for the 787," Nesbitt said.
Within an hour of Wednesday's tests, Boeing had downloaded noise data from a life-size dummy seated in seat 7H in the front cabin of the 777. Microphones in the ears of the dummy heard exactly what a passenger would have heard in that seat. At the start of the Glasgow testing last week, Boeing ran baseline tests before the right production engine was modified.
The reduction in the buzz saw noise was significant.
Another noise-reduction development being tested on the 777 is a chevron, which is attached to the exhaust duct of the right engine, as well as to the secondary fan nozzle at the end of the nacelle on the same engine.
The sawtooth pattern of the chevron reduces engine noise -- that heard in the rear cabin as well as the "community noise" that is heard on the ground when a jet takes off. Chevrons will be used on the 787.
A couple different chevrons will be tested as part of QTD2, including a "smart" chevron. The metal alloy changes shape in flight, depending on temperature.
Environmental concerns such as jet engine emissions and airplane noise have become much more important to the industry in recent years, and are driving both engine makers and airplane manufacturers Boeing and Airbus to make their products more "green."
During tests at the Glasgow site with a 777 in 2001, Boeing found that two engines equipped with chevrons made no more noise than a single engine without the chevron.
The Boeing test facility is in the northeastern corner of Montana, about 25 miles north of Glasgow. The airfield was used to train B-17 pilots during World War II and in late 1944 a camp was built at the site to house German prisoners of war. In the 1960s, a Boeing B-52 strategic bomber wing was located there, at what by then was Glasgow Air Force Base. The base closed in the 1970s and much of the property, after sitting idle for years, was purchased by Boeing as an aircraft test facility.
Current testing started Aug. 2 and is set to end by Aug. 25.
The serrated chevron works by producing a better mix of the exhaust gas from the engine's core, the fan-driven bypass air flowing through the nacelle and the ambient air that passes around the nacelle. When these three air flows are properly mixed, engine noise is reduced.
A shock wave produced by the exhaust creates a loud noise that hits the rear fuselage, creating sound passengers can hear. The chevrons will reduce that noise.
On the 787, it will mean Boeing will not have to put as much sound-proofing material in the plane's sidewalls, helping reduce the 787's weight and improving its fuel burn.
The current QTD2 tests will pave the way for QTD3 in a few years. That will test noise reduction technology for the next new Boeing jet, a 737 replacement that could be flying by around 2012.
Boeing has not yet decided when it will launch development of its next plane after the 787, but has said timing will be driven by engine makers.
But efforts by Boeing and others to make airplanes more efficient and more quiet aren't likely to end here.
Said Walt Gillette, vice president of 787 development:
"It's a never-ending quest."
If you want on or off my aerospace ping list, please contact me by Freep mail not by posting to this thread.
This level of effort for noise reduction should be in all segments of aviation. The main political objection to airports is noise, and fighting the locals can be incredibly difficult.
And as Boeing and GE are demonstrating, it need not be.
When I was an aerodynamicist at a major jet engine manufacturer 20 years ago, we had exactly one guy in the acoustics group. Basically he just ordered noise suppressing nozzles, and that was his job in life.
But obviously that is no longer the case. Which is great.
I have a summer place way up in the mountains. It is on the flight path south about 60 miles from Seattle. The big jets from Seatac or the military from McChord are not much of a noise problem. However, the small general aviation planes are a noisy pain in butt. Especially when they decide to practice stalls or circle time after time.
Why can't the smaller planes be quieter? I would never be able to operate a car that made that much noise and disturbed that many people, so why are the damn things so noisy?
thats the guy from boeing doing a alieron roll in a 707
I don't know of too many practice zones "up in the Casdades", especially where there are no clearings. For one, the air is too bumpy there. Plus, if there are no clearings, there's nowhere to practice emergency landings.
So where is your property - roughly? I've got a 60 acre field in front of my place that pilots use as an emergency landing strip almost daily.
Being a licensed pilot, I don't care. Smaller planes are loud due to unmuffled engines, and prop noise. Deal with it.
Funny how science is driven by demand. Always has been. Which is why some fields grow and others languish even though, abstractly, each is of the same worth.
Stealth technology...
No doubt, this is what we learned from building stealth military aircraft.
Some European countries mandate mufflers on piston-engined GA airplanes.
An outstanding question.
Prop "technology" has only recently started to make some simple moves in the direction of noise reduction; continuous sweeping of the tip leading edge, called the "scimitar" prop is an example of reducing local mach number to reduce noise and increase efficiency. There are also companies now including tuned mufflers that are actually worth calling "mufflers", unlike some of the older examples.
It's just been the result of inertia and backwardsness at the GA companies. For example, Hartzell propellers makes a big deal out of the fact that they now build the props using 5 axis NC machines. Big Deal. That's been going on in the jet engine business for something like 25 years now. They also probably only started doing CFD based aero design in the last decade; before that, it was done using empirical data for standard airfoils - about the same way it was done in the 1940's.
There isn't any good reason that GA can't reduce noise, and thus reduce the objections to GA airports and operations.
Unfortunately true!
Until it's important....it's not.
And when "community groups" start closing their airports by agitation with the local airport commissions, they'll learn to give up those 10 or 15 lousy lbs of added weight!
Been there, done that. It's not pretty - just ask the AOPA regional guys, who spend their whole lives trying to keep the airports open.
After the base closed they used some of the housing and build a small retirement community called St. Marie but there's only about 150 residents there. Glasgow isn't very big now either with about 2000 or so.
I asked a reasonable question and other posters took the time to give me some reasonable answers. You, however are the kind of asshole that ruins almost every activity.
I will deal with it. I will deal with it by trying to shut down small aviation airports, complaining to the FAA about noise and doing everything I can to eliminate your noise by making it difficult and expensive for you to fly. Deal with it.
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