Looks like we will soon see those huge winglets on WJ. A few questions that some of you may be able to answer. They do not specify If the few next a/c to be delivered will be immediately fitted with the winglets, I guess the answer is yes but you never know.
But apart from fuel-economy (therefore increasing range and engine life) how on earth could that reduce noise on landings and take-offs?
Mark_D. From Canada, joined Aug 2001, 1447 posts, RR: 6 Reply 1, posted (9 years 11 months 4 weeks 1 hour ago) and read 1885 times:
SafeFlyer-- But apart from fuel-economy (therefore increasing range and engine life) how on earth could that reduce noise on landings and take-offs?
I guess it's a related consequence of the (slightly) lower fuel-burn -- for the same engine type it doesn't have to run at as high a throttle setting hence it's (ever so slightly) quieter. Seems to me the writer really overstates the case there, however.
It's kinda too bad from a passenger's point of view as they'd be just one more viewing obstruction around the wing area. But them's the breaks.
I would imagine that every new NG off the line from Boeing (starting from maybe a few months from now, if not immediately) is going to have them installed right from the factory.
Mark_D. From Canada, joined Aug 2001, 1447 posts, RR: 6 Reply 3, posted (9 years 11 months 4 weeks ago) and read 1859 times:
Lymanm--I would venture a guess that the reduction in wingtip vortices would reduce noise. Items that cause drag are noisy, eg - the landing gear/flaps.
I'd say that'd probably be no more than a 0.1 db difference, and that at a range of 100m or so. Farther away even less. Especially at ~150knot takeoff and landing groundspeeds.
C172Akula From Canada, joined Mar 2001, 979 posts, RR: 5 Reply 4, posted (9 years 11 months 4 weeks ago) and read 1826 times:
I believe it was an article in Aviation Week or something like that, apparently a lot of noise is caused by the gears, flaps, etc on an a/c on approach. They are looking at ways to streamline those parts of the aircraft to further reduce noise signatures.
Can't wait to see those winglets on the 37's here around YYC. I was actually just wondering about this today, remembering a thread about it at least 2 months ago.
Mark_D. From Canada, joined Aug 2001, 1447 posts, RR: 6 Reply 5, posted (9 years 11 months 3 weeks 6 days 23 hours ago) and read 1804 times:
C172Akula--apparently a lot of noise is caused by the gears, flaps, etc on an a/c on approach. They are looking at ways to streamline those parts of the aircraft to further reduce noise signatures.
Gear and especially flaps, slats and spoilers (and speedbrakes too, if applicable), yeah I guess all that would amount to a couple db or so, at 100m. But not wingtip vortices!
Also a couple db from a flying-dirty configuration I still think is a paltry amount if it compares to 90db or something like that from the engines (and way more when the reversers get used). Though maybe there's some attention paid to it anyway these days, trying to look at every last possibility in a bid to meet upcoming Stage 4 noise requirements.
Lymanm From Canada, joined Jan 2001, 1133 posts, RR: 1 Reply 6, posted (9 years 11 months 3 weeks 6 days 22 hours ago) and read 1764 times:
"Gear and especially flaps, slats and spoilers (and speedbrakes too, if applicable), yeah I guess all that would amount to a couple db or so, at 100m. But not wingtip vortices!"
It may surprise you to learn that wingtip vortices are the most influencial forms of induced drag. At high speed cruise, the vortices account for almost 90% of all drag. At lower speeds in the landing configuration, it is not as big a factor but nonetheless prevalent. Flaps and gear (including struts and doors) account for much of the drag (and thus noise), but the wing displacing huge amounts of air culminating in the vortices is still quite noisy. By no means to winglets eliminate vortices altogether, but it certainly reduces the vortex profile, hence resulting in less noise.
In any event, the power settings on final approach are relatively low to begin with, and perhaps a few hundred pounds/hour difference between winglet/non-winglet aircraft certainly isn't enough to make any audible difference. Without knowing for sure, I'd bet that there aren't any power setting differences on the glideslope between the winglet/non-winglet 737NG.
Regardless, I think we can all agree that the difference is negligable to the average human ear.
B2707SST From United States of America, joined Apr 2003, 1350 posts, RR: 60 Reply 7, posted (9 years 11 months 3 weeks 6 days 20 hours ago) and read 1711 times:
Boeing claims a 0.5 - 0.7 EPNdB noise reduction with its blended winglets. http://www.boeing.com/commercial/737family/pf/pf_winglets.html. Given that the human ear can distinguish down to a 1 dB difference in sound intensity, this benefit is marginal at best. However, Boeing states that:
“At noise restrictive John Wayne airport in California, installation of blended winglets would take a Next Generation Boeing 737 from a category A to category AA. This could mean an additional 39 flights a day, which is extremely significant. "
This is probably a special case in which the standard 737 sits right at the edge of a noise category. I doubt a 0.5 EPNdB gain would result in any operational advantage at most airports.
The winglets also add about 480 pounds to the plane's empty weight, which is why short-haul operators do not seem eager to add them. The fuel savings claim for long-haul 737 flights is 3.5 - 4%.
Mark_D. From Canada, joined Aug 2001, 1447 posts, RR: 6 Reply 8, posted (9 years 11 months 3 weeks 6 days 19 hours ago) and read 1700 times:
B2707SST--Boeing claims a 0.5 - 0.7 EPNdB noise reduction with its blended winglets.
Oh, you beat me to it (this is the link I was going to post:
http://www.boeing.com/commercial/aeromagazine/aero_17/winglet_story.html where they say among other things, "Environmental benefits include a 6.5 percent reduction in noise levels around airports on takeoff " which would amount to a reduction of ~0.27dB. More than the 0.1 dB I had figured but still not very much, overall)
Lymanm--At high speed cruise, the vortices account for almost 90% of all drag. At lower speeds in the landing configuration, it is not as big a factor but nonetheless prevalent.
I don't know about either of those contentions. 90% is pretty high (I thought it was more like 40 or 50 percent, as a maximum for standard airliners at high speed cruise). And at landing speeds I don't think it'd be a prevalent component at all --I'm guessing its contribution around 10%, given all the other drag components elsewhere over the airframe and the vastly-lower leading-edge air compression at takeoff and landing speeds contributing to wake effects.
It does sort of surprise me though that winglets weren't commonly used sooner on commercial airliners, given the benefits.
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