Interesting, I remember reading a piece in the RAeS journal years ago where they estimated the noise from some of the proposed super-jumbo aircraft would exceed the limits even with the engines turned off. Surprised it's taken so long to tackle it as it least some must be from inefficiencies, a lot though is presumably required if you're turning a few hundred tonnes of air through 90 degrees to generate lift.
Japan's aerospace agency hooks up with Boeing to make planes quieter when they land
The Japan Aerospace Exploration Agency (JAXA) has teamed with Boeing on a joint research project to make quieter mid-sized passenger planes – by figuring out how to cut the noise generated by their airframes. Aircraft noise is an issue around the world, and the aviation industry is keenly aware that its social licence depends …
COMMENTS
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Saturday 21st August 2021 22:48 GMT anothercynic
The easiest has been tackling the most obvious source of noise - the engines.
Now that turbofans are at the point where they are arguably quieter than the latent noise generated by all other parts of the plane but the engines (and even unducted fans à la the GE36 UDF or the Safran RISE), the hard work begins. After all, the wing is meant to be ultra-efficient (with few vortexes, with laminar flow etc) for flight, and now we're having to make the wing less efficient and in fact be a piece of resistance to slow the plane down and to make it drop but not in a way that makes it go "boom" or leave a crater at the end of the runway, all whilst being *quiet* to avoid noise on approach and finals.
The aerospace engineers have their work cut out for them.
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Monday 23rd August 2021 11:06 GMT An0n C0w4rd
Re: Why not go the whole hog
Not to mention the small issue of hydraulic and electrical power needed for the flight instruments and control surfaces. As ably proved by the 737MAX debacle, muscle power alone is not enough to move control surfaces on a modern aircraft
I guess you could point to the RAT (Ram Air Turbine), but that only provides power for very basic instruments and controls.
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Friday 20th August 2021 13:07 GMT I ain't Spartacus
Re: Why not go the whole hog
G R Goslin,
The aircraft is insulated - so I doubt passenger screamage will be externally audible. So that's not a problem.
The problem is clearly operating engines at low level. So I think the solutions should borrow from existing, well understood, technology. I suggest we consider aircraft carriers.
In order not to have to slow the plane so much, we can dispense with slats and flaps, simply have a few arrestor wires - and that will slow the plane down nicely. You'd get some problem with tyre noise, carrier landings can be have significant tyre squeal. Maybe oil the runways, to make them extra-slippery?
Or another, long forgotten, piece of carrier tech as tested by Eric Brown. Simply remove the undercarriage entirely and have a rubber trampoline thingy fitted above the runway. Simply stall the aircraft above that - and have a nice bouncy landing. Extends aircraft range by saving weight as well - actually tested by the Royal Navy due to the pathetically short range of early jets.
We can also think further into this. Why must people put up with low level engine noise? Simply have catapult launch. With a decent length of runway, I'm sure you could get the plane up to takeoff speed, and with a nice ramp get the aircraft launched, and only turn the engines on, once above a certain height.
It all seems very sensible to me...
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Saturday 21st August 2021 22:49 GMT JamesTGrant
Re: Arrestor wires
Can’t see any down side to this - you could even make the landing runway 30deg steep and the aircraft wouldn’t have to slow down before getting snagged. Big fuel saving - could turn the engine off and coast the last little bit.
If it went wrong it’d be in slow motion anyway so no damage would be done…
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Friday 20th August 2021 15:54 GMT Anonymous Coward
Re: Why not go the whole hog
>I'd have thought it obvious that the engine noise would reduce when throttling back to descend
Joking aside it's a big part of our flight path planning.
Decrease engine power slowly and descend slowly you have slightly less engine noise - BUT you spend a lot more time at low level above houses.
Fly at full power for longer and then approach the airport like a dive bomber you are only at low level inside the airport perimeter - BUT it annoys passengers who don't enjoy roller coasters and occasionally you experience lithobraking
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Friday 20th August 2021 16:20 GMT werdsmith
Re: Why not go the whole hog
I live under an approach and I love the noises. The flaps deploying, the undercarriage going down all make noises I recognise and I can tell plane types apart purely by their sound now (I miss the distinct flap howl of BAE 146 / RJ180).
This morning one plane made a loud rattling noise that had me running out to see what was up.
The engines do make a whine on approach, you can hear it throttling up and down adjusting slope.
The old planes that do freight very early in the morning are very loud.
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Saturday 21st August 2021 22:49 GMT anothercynic
Re: Why not go the whole hog
And of course there's a *lot* of work done by Eurocontrol, NATS and others to reduce the amount of 'loiter' by jets in holding stacks, which also adds to the noise profile, and going for other, alternate approach and landing profiles.
I understand London City (LCY) uses the latter, with a steeper approach angle to not only get through the housing estate jungle but also to reduce the noise in the area. Embraer, Bombardier and Airbus all have specific configurations for such approaches that they developed in cooperation with LCY because it's useful elsewhere. :-)
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Friday 20th August 2021 13:40 GMT Timbo
Re: Others use ...
"Outside broadcasters find fur fabric very good as reducing surface turbulence. It would make planes look nice too."
Two problems:
1) The fur would absorb water so flying through a rain shower, would cause the weight of the plane to increase significantly, resulting in either a need for bigger wings and/or more engines.
2) You'd need a lot of fur...the animal rights activists would not be pleased and thefts/kidnappings of domestic animals might increase as the criminal trade in fur would increase.
A better idea might be to put dimples on planes (as it works for golf balls), or maybe design the body of the plane with flutes (like the rifling inside a gun barrel) - both of these supposedly make for less air resistance and better directivity....
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Friday 20th August 2021 14:14 GMT Mike 137
Re: Others use ...
"animal rights activists would not be pleased
Actually it's fur fabric that's used, so no animal rights issues. It's used as the outer layer on microphone wind shields to eliminate turbulence at the surface of the shield, so it has to have an open weave to avoid blocking the sound. Some folks who don't understand the principle have tried real fur, but of course the impervious leather stops the sound getting to the microphone.
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Friday 20th August 2021 14:18 GMT Mike 137
Re: Others use ...
"design the body of the plane with flutes"
It's not the flutes on a bullet that make it fly straight - it's the spin imparted by the spiral flutes of the gun barrel. I don't think most passengers would appreciate a plane that revolved at high speed on its longitudinal axis.
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Friday 20th August 2021 15:10 GMT Mike 137
Re: Take a cue for the Shuttle?
I've never flown an airliner, but my impression is that flaps are engaged quite a long time before any parachute could be used effectively and safely. Military planes deploy the parachute after touchdown, not while in the air. If they did the latter they'd probably just fall out of the sky.
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Saturday 21st August 2021 02:02 GMT Denarius
Re: Take a cue for the Shuttle?
Was an issue with early fiberglass gliders. Some had a tail chute to get a decent descent rate. Big problem if pulled too early. Fences are fatal. The chute could be released but then risks being lost. Chute was way too small to be a ballistic recovery device, unlike the ones used in some ultralites
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Saturday 21st August 2021 12:08 GMT Lars
Oh dear
@CoffeeBlackest
The ugly voice of English exceptionalism speaking again and again.
Japan is a bigger richer country than Britain with a stronger currency too.
The Japanese space agency JAXA is doing/has done more than the "British space agency" alone ever.
This repulsive idiotic attitude is killing you from inside, rightfully so.
https://en.wikipedia.org/wiki/JAXA
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Friday 20th August 2021 17:28 GMT I ain't Spartacus
Re: Simple fix
I worked at the end of the runway at Heathrow. It wasn't Concorde landing that caused us to have to stop work for a minute twice a day. It wasn't all that noisy. Takeoff on the other hand... As you say though, it did mean that you didn't tend to notice the other planes so much.
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Friday 20th August 2021 18:42 GMT bombastic bob
golf ball exterior
there is some evidence that the appearance of the skin of a golf ball not only reduces the air drag during the ball's flight, but the noise it would generate as well.
I have to wonder what effect this would have on airplane parts...
(parts of the article already allude to existing features that might behave similarly, like lots of small holes in a control surface, which could also reduce weight)
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Monday 23rd August 2021 18:43 GMT DS999
Re: golf ball exterior
That works for golf balls because they are rotating at thousands of rpm. If you shoot a golf ball out of an air cannon with little or no spin, it actually performs worse than a smooth ball due to INCREASED drag. If dimples worked on a wing, we'd have dimpled wings. It isn't like golf balls are a secret to aerodynamic engineers.
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Friday 20th August 2021 20:20 GMT Anonymous Coward
"Turbojet and turbofan engine designs have helped by increasing bypass ratios,"
Isn't that basically the differentiation between a turbojet and a turbofan? Aren't they essentially the same, except the turbofan has a higher bypass ratio, so most of the thrust comes from the fan part, not the jet part?
Asking because I'm sure a few Reg readers will know for certain.
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Friday 20th August 2021 21:04 GMT Anonymous Coward
Re: Owls
In my corner of the world, which is under the flight path of our friendly neighborhood military base, one could deduce how to pronounce the first part of the FQUROH acronym from how little care or respect the military seems to have for the residents (and schools and churches and businesses and parks/playgrounds) over whom they fly. Honestly, if one MUST learn how to race in at full throttle (which I am sure pilots do need to learn to do safely), can not that be done at a base that is NOT totally encircled by built-out residential development (much of which pre-existed the base)?
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Saturday 21st August 2021 02:11 GMT Denarius
Re: Owls
infinite regression problem added to stupid/corrupt (but I repeat myself) local government. For airports good access is required. So airport built in scrub away from all and sundry. Developers see great road, make donations, and build suburb next to and eventually around airport. Cue noise from locals demanding airport goes away. Jandacot in Perth WA is a classic case. Miles from anywhere, used to trail bike in empty scrub disturbing only kangaroos. Now it is surrounded by suburbs, which whine about aircraft noise and is on top of a major underground water supply for city, now being polluted by garden waste, leaking pipes etc.
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Saturday 21st August 2021 22:51 GMT John Brown (no body)
Re: Owls
"Less joyously, this sort of nonsense comes round every ten years. Last time it was Cambridge with some big aerospace boondoggle to develop silent flight. I think results so far are nil."
I suspect the problem is no one is really building new planes. A new plane takes many years from concept to service-ready, so most new planes are adaptions and improvements on older models, thus seriously reducing the development and certification phases.
The research ideally needs to come up with simple adaptions that can be retrofitted to existing planes which then must be mandated in at least some jurisdictions, forcing the manufactures, owners and operators to take it seriously. They won't spend money they don't have to unless there are savings to be made in one opr more of fuel economy, lifting capacity or fine avoidance.
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Monday 23rd August 2021 10:12 GMT rg287
Re: Owls
Less joyously, this sort of nonsense comes round every ten years. Last time it was Cambridge with some big aerospace boondoggle to develop silent flight. I think results so far are nil.
Nonsense? Boondoggle?
Nobody is trying to develop silent flight. that would be stupid and impossible. Any aircraft will move air out the way and generate some sound. They are simply seeking to minimise that. This is extremely useful research in the general sense since it furthers understanding of fluid dynamics, turbulence, vortices, etc which have broad ranging applications in many sectors.
Previous projects have improved things like the design of landing gear, which makes a measurable difference to landing noise.
Nobody is going to announce a new (magic) "silent" airliner. But the results of this sort of work feeds back into existing designs to incrementally improve certain components as you go from (say) the 737NG to 737MAX or A330 to A330neo. Older planes were louder than newer planes, and it isn't just down to the engines.
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Sunday 22nd August 2021 21:58 GMT martinusher
Overlooking the obvious
The turbulence from the control surfaces is all part of the process of destroying energy as the plane lands. You've got anything up to a couple of hundred tons of metal and stuff that's descending from several miles up so all that potential energy has to go somewhere. You're also trying to slow the plane to a reasonable landing speed so there's no use converting that potential energy into forward motion. So you deploy flaps, slats and what-have-you to change the aerodynamic properties of the wing from ultra-efficient to 'not quite a metal parachute'. All the inefficiencies result in turbulence, and so noise.
I'm surprised that nobody's thought of this before, its obvious. (Its unfortunate that we can't recover all that energy we spent lifting and accelerating the plane for the flight. Flying was always going to be a relatively inefficient way of getting about.)
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Monday 23rd August 2021 11:12 GMT xformer
Well, I strongly disagree with the sentence "Turbojet and turbofan engine designs have helped by increasing bypass ratios, thereby improving efficiency and dramatically reducing sound". That is simply not true.
I live near an airport and I know the sounds of all the airplanes that buzz around here. Take for example the GE90 used by the Boeing 777 airplane. This is a high-bypass turbofan aircraft engine and it is much louder than than other engines. The high-bypass reduces the rumbling of the engines a bit and certainly not dramatically. Unfortunately it generates and extremly loud high-pitched whistling sound, making the noise even more unbearable than those of engines with a lower bypass value.
The Boeing 737-800, which uses CFM56 engines (high-bypass ratio, you guessed it) is *extremely* loud. It is one of the most annoying planes that are in use. It is even louder than some 4 engine planes.The noise is much louder than the one Airbus A320 classic engine planes. It is the loudest small plane that I know of.
The same holds true for the much-praised Airbus "neo" engines (PW1100G-JM and LEAP-1A). They are a bit less-noisy than the "ceo" engines but also have this extremely annoying whistling sound which make them even harder to bear, especially shortly after take off.
Even the Airbus 350 with it's Trent XWB with a "reduced acoustic mode scattering engine duct system (RAMSES)", a quieting engine and "zero splice" is quite loud.
I know of only two planes that are dramatically less noisy: Boeing 787 and Bombardier CS-100/-300 (now called Airbus 220). The Boeing 787 uses GEnx-1B and Rolls-Royce Trent 1000 engines. The CS-100/-300 uses PW-1500G engines. All of them are also high-bypass engines. So what is the difference? The B787 uses engine nacelles with chevrons. I do not know what makes the PW-1500G less noisy.
All-in-all it is not the high-bypass ratio that makes plane engines less noisy. That is simply not true.