Video: A Silent Rotor Blade Paves the Way for Super-Stealth Choppers

That should say "manages to pare down the blade-vortex interaction".

Can they use this technology on my PC cooling fan? Because that thing gets WAY too loud.

So with less sound waves created in the equation here means that the copter becomes more efficient overall. Assuming, of course, that the new blades have similar mass to the current ones.

Sure would make the ride more pleasant.

can we also use this in airplanes?

@extreme I think the rotors are in a significantly different situation than turbines in a jet engine. Maybe prop airplanes could use it, but I'm not sure how it would work with blades that are as turned as the ones inside a turbine. Who knows though, it'd be awesome if they could.

I don't know of any particular reason why they wouldn't work at all in a turbine, but if any, its because they wouldn't fit... You would have to enlarge the engine which could reduce its efficiency. Now, for private jets, this would be a must as silence is always a wonderful thing...

Honestly though, I don't see why this couldn't be applied, at least in some form to any fan. It may reduce the amount of thrust, but it sure makes it a lot more pleasant. You can always up the RPM on a motor, whereas this is a great thing that could find its way into just about anything...

There will be people who complain about helicopters being too quiet. Like people who complain that Priuses are too quiet, there will be birds who say, "Hey, I almost got chopped in half cuz some idiot decided to put some quiet rotors on his dang helicopter. Can I sue?"

Seriously, this is good cuz noise pollution is starting to get out of hand, especially if you live in a large city with police helicopters, news helicopters, medivac helicopters, or if you live on or near a military base.

When are they going to invent the noiseless jet engine? When I used to be in the USAF, all DAY and all NIGHT all you heard was a damn fighter soaring up above. Got quite annoying especially during the early morning trying to get a few extra Zzzzs.

I don't think this technology would be applicable in turbine engines since the blades in a turbine rotate inside a duct with very little space between the tips of the blades and the inside of the duct. No space means no vortices to speak of, which means no beating sound like with that of heli blades. Most of the noise in a turbine engine is produced by the shearing of the exhaust against the still surrounding air, not by the rotation of the blades inside the engine.

But it could certainly be applied to propeller driven aircraft, piston or turbo-prop.

Yeah, I've no idea if it would work for a jet engine either. But current tech is definitely able to direct the sound; a flyover by a B-2 Stealth bomber I saw once was eerily silent, until the bomber had passed over head--ie too late.

There'e no way this new blade could produce only 3 or 4 decibels. Rustling leaves are about 30 decibels. Eurocopter's web site www.eurocopterusa.com/news_features/2010/02-22-10-heli-expo-2010-innovation.asp says there is a 3 to 4 db noise reduction. It's a significant improvement, but the helicopter will still rattle your windows. Stuart, do do a little research before you make such mindless claims.

This is nothing new. Angled rotor blade tips are used by many helicopters in production like S-76 or AH-64. You cannot hear the typical rotor noise while in cruise in these helicopters. RAH-66 went a little further with the rotor noise reduction, and this seems to be an improvement of the same technology.

I always find it funny when this happens but I lie to play around with diy UAV's and I been working quiet prop that will look a lot like this when its done.

hey at least I know my idea works now. lol

It won't work on a fan that doesn't move through the air in the direction of its plane, and that includes all stationary fans, also all fans that have a cylindrical cowling around the blades like CPU and hovercraft fans do.

It also doesn't affect fans that move through the normal axis of their planes, like propellors on airplanes, so keep working at it, dex draco.

The mass of an object that does not accelerate linearly has no effect on efficiency if the objects' velocity remains constant. Which helicopter rotors usually do, since lift is altered by altering the angle of attack of the blades while their rpm remains the same.

The remark about decibels is right on. To begin with, the decibel is a factored logarithm of a ratio, and 3dB represents a doubling of sound energy - a ratio of 2 to 1 (6dB = 4:1 ratio, 9dB = 8:1, 10dB ~ 10:1. So the author omitted to say which two energy levels that 2:1 ratio is between.

Stuart Fox: with respect, you need to take a science course or at least a couple of refresher courses. I'm running smoothly on little more than grade 12 physics and a long history of inquisitiveness - no degrees here, arts OR science! As I've refrained here before: more 'Science', less 'Popular' could not hurt this publication or its intended readership. It isn't wrong, it isn't hard, it isn't off-putting, to try to raise the level of understanding of your readership instead of succumbing to it.

Please?

I expect this makes the helicopter more efficient? Kudos on the 3-4 decibel callout.

"For all the government conspiracy militia nuts out there,.... "

hey Stuart Fox are you stupid or what? since when is a fucking helicopter a government conspiracy??

some morons just have way too much time writing stupid articles like it is big news.

Silent aircraft have been used sucessfully in combat.

Look at the Web Site for Lockheed model YO-3A

I think that many that comment on this do not understand how a helicopter works. The mail rotor IS NOT a big fan pushing thrust down. VSTOL aircraft work in this way, but NOT helicopters. The rotor is a airfoil wing just like in any aircraft. This wing uses Bernoulli's principle to create lift,just as in fixed wing aircraft. The difference is that instead of requiring forward motion to push the wing through the air, a rotor based aircraft like a helicopter or gyro-copter moves the wing through the air without requiring forward motion of the entire craft. The POP sound that is created has two causes. One us the ends of the rotor going super sonic and causing mini sonic booms, you could possibly prevent this by making the rotor V or W shaped in order to get the same lift area but shorter and thus slower tip speed. The other cause of noise is as described here.

This is a three part problem.

The Engine and Transmission are also very loud.

Why shape just the tip? That's where most of the noise is made, I'm sure, but I would think that the rest of the blade, or at least the outer 2/3 would also be a significant sound source. Specially shaping the entire blade looks like the way to go.

As for jet engines, fan blades do have quite extraordinary shapes these days, like the scimitar-shaped blades on Rolls-Royce Trents.

You might want to look at the GE90-115 turbine...specifically the blades. In fact the patent on this new helicopter rotor could face a serious challenge from GE as the turbine blades on this engine look very much like the "crook" in the rotor blade pictured.

This is a good thing bad thing...

A good thing... that an enemy can't hear it

Bad thing...our guys love the sound as it means help is on the way!

I really love all the internet fools who use their vague understanding (or misunderstanding) of 12th grade General Physics to usurp the scientific authority of learned and proven engineers, physicists, chemists, and other authorities on scientific matters. You are an embarrassment to imbeciles everywhere.

Well, as a layperson, here are a few observations that seem to make sense.
Projectile weapons have silencers, why not noise abatement exhaust systems on piston engined and small turbine engine aircraft?
The problem of prop wash has been addressed for more than half a century, and it's certain that if there was a way to have achieved this development by covert military R&D, it must surely have been discovered decades ago. Applications for such an aircraft would be quite numerous, making said potential aircraft very desirable - as desirable as jets, stealth, breaking the sound barrier, or any other major military developments created decades ago.

Hence, the silent helicopter is old news.

Having read the testimony of eyewitnesses to the use of such helicopters allegedly already in existence since the 1970s, the above article comes as no shock. (No pun intended.)

this is cool!

I'm all for quieter copters.

My town bought a couple of new "stealth" police choppers (for a price each of 10x what the choppers they were replacing cost) -- but they are INCREDIBLY noisy. Particularly in a steeply banked turn (which the police pilots seemingly LOVE to do). The new copters *are* slightly quieter -- but only from a couple of angles. Mostly, they are hugely noisy. Much louder than the old Bells.

First, let me start by saying that I am an engineer for a large company designing rotary wing aircraft. I specifically work with rotor head and blades, so this is kind of up my alley so to speak.

Second, "popular scientist" while I usually have issues with what Stuart Fox writes, I have to say that this "article" was surprisingly technical. The only mistake was the dB issue which is a common mistake.

Third, swept tip blades have been around for a LONG time. This is just an improvement on old technology. That being said, not very many helicopters use it and most current designs don't work that well. This is cool.

Last, "dlapham" rotor blades do not work like airplane wings and older blades are symmetric. We have gone to a non symmetric airfoil design for efficiency reasons. A rotor system does not work like a airplane wing OR like a fan. I teach multi day classes on rotor wing design theory and this is not the place to discuss the inner workings of the system. However, the noise is caused by vortex interactions like the article states, not by the tips breaking the sound barrier. We design rotor system to operate just below that limit because the efficiency of the system degrades greatly as the tips approach mach 1. The tip speed is one of the major design constraints.

Shaped exactly like a bird's wing.

Albert Einstein said to "Look deep into nature and you will understand everything better".

Wow, this is amazing. What a breakthrough!

Jerry
www.total-anonymity.cz.tc

Ok so it's not as impressive as the 'copters in that Mel Gibson conspiracy flick from the late 90s, but it is cool...
www.bieres-et-vin.com

this is totally totally mad - probably some of the coolest technology going - It definately makes the whole heli look more vicious too.

What I thinks great is this will further along other supportive technologies too - and also potentially provide a future of less noisy air travel!!!

Harma

Huck is correct, this is not necessarily a new concept. Yes it may be improved upon. The question that I have is, was there a 3-4 decibel reduction while the aircraft was on the ground at full RPM, or was it measured while in flight at an altitude of 500 feet AGL for example.

The majority of noise from a helicopter comes from the tailrotor. This can be observed by listening to a hughes 500 D aircraft in flight with a 2 bladed tailrotor system vs. a 4 bladed tailrotor system. The four bladed system is much quieter, although less efficient on the Hughes 500 D.

Furthermore, it wouild be interesting to see if this technology would be quieter under all power settings. Most helicopters have a tendency to have blade poping in a descent with low power settings, therefore I would want to see if this system remained quieter throughout various speeds, and power settings.

As a resident formerly near the Reno,NV airport and Former home to the Vietnam Era F-4 (recon-fighters) in our NV National Guard.I can attest to the fact that their single engine was able to knock 10x the pictures off my wall,awaken me with 10x the force,etc,etc...as maybe somebody out there knows of a more noisy aircraft??I dont.Afterburner glowing a full 2-3 minuites and of course youve lost sight of it in 30 seconds......

Hey I lived under the takeoff path at reno,nv airport and wouldnt have ever complained,and I hope this isnt misinterpreted as one.I loved em every time.Now NV has the aging though still awesome to C in form the C-130's.Both beautiful in very diff. ways

kevin

and a P.S.

to
EzMaTezPez

History has proven that almost every modern invention/appliance we have,at one time had,many people calling their ideas idiotic and impossible.....

kk

NASA, during the 70' and 80's did extensive research on helicopter rotorcraft noise using a YO-3A silent airplane. Research gathered from the YO-3A led to advanced understanding of helicopter rotor blade noise and to the development of new wind tunnel designs for testing helicopter rotors. I am sure the developers of this "silent" helicopter benefited greatly from that research.

The YO-3A was originally developed for use in Vietnam (1970-71) for the U.S. Army for low altitude night recon missions using the 1st second generation night vision system. 9 of the 11 YO-3As operated for 14 months in Vietnam. They never took a round or were shot down operating at 800 to 1500 feet.

The NASA YO-3A, originally Army-Lockheed YO-3A 69-18010, is the world's quietest "flying microphone." NASA's YO-3A is the only flying example of the YO-3A. See www.yo-3a.com.

These silent blades will make these helicopters that much better for getting out troops in and out safetly. People also wont have to wear or carry much more equipment when riding in these black hawks.

They should try taking a hand at quieter wind turbine blades.
My father taught flight school after serving in Korea, and he and I chased jackrabbits in what he called his up-side-down egg beater (along with chasing tornadoes in it after taking the doors off).
I've made around 400 RC planes (no choppers) but I've been building wind turbines (as a hobby not a living) for around 30 years and have done a lot regarding noise reduction (especially for Air 403's that if mounted in town, soon have town meetings, banning wind generators in town due to the noise).
Only a 7th grade education, so I'm sure I'm gonna get picked on here (that's okay I'm used to it). But I can share a word of wisdom with the 12 graders (educationally speaking) here, that instead of stating something as a fact (even those with PhD's seem to make this mistake) I think it works best when I say "I think", instead of "I know".
Cuz next thing you know, what you knew, tends to be dis-proven, or just replaced with something more accurate (education level seems to be little protection from that one).
And before someone else says it, yes, there is a difference in airfoil, of something being pushed by the wind vs something pushing the wind, or using the airfoil for lift vs propulsion (or at least, so I think ;).

PS before someone shouts "dang hippie" at me....
I know all to well sometimes you have to fight, but not being a cop or military, I had no right, using violence against violence would have ended up with me in jail and I had a son (single father).
And if more lives are saved by destroying the enemy, then this is the best application.
But I fought, to not destroy my enemy, nor die in the process, of stopping him, and I won.
Not against war when it is necessary, but whenever I have to physically defend myself, I cringe, for not being smart enough to able to find a better way, before that is required.

Sometimes, I do understand, we have no other choice.
That does not mean, I dont await the day, that we do.

if anyone is moderating here, please delete my last post above, I meant to post it on a different page and posted it here on accident

This would be a good compliment for the MD Notar

for those of you who didn't realize, my screen name is a military helicopter operational call sign. (just ask any combat vet who's been rescued by a Super Jolly Green Giant)

I spent a few years in a helicopter maintenance unit working these impressive birds back in the day. The three most impressive aspects of these birds are:

a) the raw power eminating from them on the ground is so intense you can feel it through the air several hundred feet away from the aircraft,

b) for it's size it is one of the fastest and most most manuverable helicopters flying. It has a top speed of 200 knots (a litttle over 200 mph) and is capable of perfoming FULL loops and barrel rolls. (in tech school at Seppard AFB, Texas, I witnessed a CH-53E Super Stallion {same basic aiframe, more engines, bigger rotors} of the USMC perfform a Hammerhead Stall), and certain variants have a Max. Payload Rating of 20 tons (40,000 lbs.), and

c) despite all the deafening noise it makes it can be right on top of you before you know it's anywhere nearby.

This last is an effect called "Terrain Masking" and has been used to great effect for decades. So quiet rotor blades"? Ehh. so what.

Most of the noise is from the interaction of the main rotor tip vortices and the tail rotor. The Hughes 500 NOTAR (NO TAil Rotor) is VERY quiet due to the tail rotor having been replaced by a ducted fan in the tail boom, with vectored exhaust.

Of course the twin rotored Boeing-Vertols (Ch-46 & CH47) make noise, but a different sound.

The CH-53, with it’s 6 (-53D) or 7 (-53E) main rotor blades sounds a lot like a C-130 Hercules!