Combined Hovercraft and Helicopter

An anonymous reader writes "Has British engineer Geoff Hatton brought us the best of two worlds with his UFO-looking machine? The US military thinks so and are investing in it. The design is sturdy (as opposed to a helicopter) and can fly high (as opposed to a hovercraft). It is based on the Coanda Effect."

Comments

sturdy? as opposed to a helicopter?

[lecithin]

I know the Marines still have CH-46 helicopters in service that took battle damage in Vietnam. Some are 40 years + and none are less than 35 years old.

Saying "The design is sturdy (as opposed to a helicopter)" is really quite a statement since the design is not in service.

Seems pretty cool though.

Re:sturdy? as opposed to a helicopter?

[localroger]

How many of those helicopters that are still flying were flown a wall at any point during their service life?

Re:sturdy? as opposed to a helicopter?

[MindStalker]

He is referring to its ability to handle midair crashes. Of course a larger version would probably handle midair crashes about as well as anything else..

Re:sturdy? as opposed to a helicopter?

[Hijacked Public]

I think they base that primarily on the fact that the rotor is protected. Many helicopters can take hits in non-critical areas but a rotor strike is almost always catastrophic.

Re:sturdy? as opposed to a helicopter?

[forrestt]

What they are saying is that the hovercopter (for lack of a better term) has the rotors protected and can bump into things and still fly. What it basically is is a small inverted squarish bowl with a fan on top that forces air down and around the sides. The fan is protected and therefore, more stable. It is controlled with fins that direct the downward air in various directions for steering. This isn't being designed for movement of people or cargo, but rather as a means to carry a small camera for recon missions. (think the small machines sent out by Skynet in the Terminator movies).

Re:sturdy? as opposed to a helicopter?

[drinkypoo]

They won't be much larger, or made out of much more durable materials (they can be flexible) because they are planning to use them as UAVs and not as manned aircraft, at least for the time being. If you RTFA they specifically talk about the design's suitability for this purpose in light of its ability to survive collisions with walls.

I'm afraid I'm going to dream of manhacks tonight...

Re:sturdy? as opposed to a helicopter?

[modecx]

He is referring to its ability to handle midair crashes

I don't think that's what he's referring to at all. Helicopters are very unstable machines, especially in hover mode, which is arguably the most important and most distinguishing feature of a helicopter. A helicopter requires hundreds of very precise control inputs a minute to remain in a hover. If you change one of the variables, you pretty much have to change all of the rest. For example, if you adjust the cyclic, you have to adjust your engine's torque and collective a tiny amount so you don't fall out of the sky, or alternatively, go flying up too fast, and you'll also have to nudge the tail rotor to account for the increased torque form the main rotor. You can think of it as a loop in a computer program that operates very quickly.

It looks like this guy's hovering craft aims to make the most advantageous feature of a helicopter much, much easier to preform, and hence the vehicle is "more stable" than a helicopter. It's probably more sturdy, too, but that's a side effect of not having blades swinging around in an arc that is considerably larger than the aircraft.

Re:sturdy? as opposed to a helicopter?

[Profane MuthaFucka]

There are two more things which you didn't mention. One is that the fan is inside a duct, which reduces tip vortices. That should make it more efficient.

The second is that it would avoid a problem which helecopters face when trying to hover out of ground effect. When more than about a rotor's diameter above the ground, the downward moving air starts to circulate down, out, up, and back into the rotor. The air moves in a circular pattern through the rotor, around, and back through the rotor again. This creates a downdraft from the perspective of the helecopter. Adding more power doesn't always help, because it just makes the air move in a circular pattern faster. The result is that the helecopter sinks when trying to hover at altitude.

If you observe helecopters hovering at altitude, you'll notice that they aren't actually hovering. They're moving forward very slowly. That's the only way to avoid that problem. You have to keep moving a little bit so you stay out of the circular rotation of air that you create behind your helecopter. If you stop completely, you're in the circular pattern and you sink unless you've got some enormous power source like a jet engine.

When you're in ground effect, the ground itself disrupts the circular movement of the air and limits how fast it can move in a circular motion. It also makes it turbulent as it deflects off the ground. The result is that you don't get a well-formed column of downward moving air that your helecopter is sitting in, thus you can efficiently hover without moving at all when you are fairly close to the ground or some other air-disrupting object like a building that you're carrying materials up to.

I would not be surprised if this device had some advantages over regular helecopters when it comes to hovering out of ground effect.

Re:sturdy? as opposed to a helicopter?

[drinkypoo]

I've heard that some of our attack helicopters can lose significant percentages of the rotor surface and still stay aloft, specifically the Apache and the Comanche (project abandoned once it was complete, your tax dollars at work.) Was I lied to? :)

Re:sturdy? as opposed to a helicopter?

[Jaysyn]

Better than mansacks, right? :D

Re:sturdy? as opposed to a helicopter?

[BostonPilot]

I beg to differ - I think the parent was probably correct about what the author meant. First of all, the design did NOT look that stable. Also, the fact that the fan is ducted means gentle collisions won't destroy the rotor system which is a pretty good feature for a small UAV. It also has a safety benefit if the rotor is ducted.

As for the stability of helicopters, if you look at the designs in the 50's and 60s, stability was a big goal. Look at Stanley Hiller's demonstration of hands off hovering of his helicopters. Over the years stability appears to have been less and less of a goal. Look at how the flybar on the Bell rotor systems has disappeared. I'm not sure why this has happened, but I'm guessing that agility has won out over stability, especially since stability can easily be added by electronic means.

I read the article, but I wasn't quiet sure how the Coanda effect was utilized by this design. I'm guessing that rather than tilt the rotor there are places where the downwash is attached (or not) and thus generate sideways thrust? I saw the little vanes moving, but assumed that was more for anti-torque - if you noticed, most of the vanes were fixed with a little bend in the direction of anti-torque (and, like the MDHC Notar the anti-torque force would be proportional to downwash and thus to torque). A few of them moved to give you the ability to rotate the machine and account for minor yawing forces not exactly countered by the fixed vanes.

Did anyone else notice where/how Coanda effect was used? Perhaps the moving vanes really are implementing the Coanda effect, but if so it's in a fairly different way than the MDHC Notar system. Did I miss something?

Re:sturdy? as opposed to a helicopter?

[comp.sci]

The secret of keeping helicopters in action for years is that due to very frequent checks and tests, almost every part gets regularly replaced.
I talked to a air-rescue helicopter pilot once and he told me they have helicopters in service that are 35+ years old, but the only original parts in them are their skids.

Re:sturdy? as opposed to a helicopter?

[muffel]

I've heard that some of our attack helicopters can lose significant percentages of the rotor surface and still stay aloft, [...] Was I lied to?

Yes, you probably were.
Unless equally sized bits break off of every blade or a *very* small piece breaks off a blade, the helicopter is almost sure to immediately literally explode from the created imbalance. And that's not a joke.
Many RC-Helicopter pilots know this from own experience -- a loud bang and the helicopter rains down in pieces (and those blades only weigh ~150g).
Also a report of this happening to a real helicopter.

Re:sturdy? as opposed to a helicopter?

[John Hasler]

> That would be news to the high voltage tower service pilot. I've watched as a helicopter
> hovered absolutely still (+/- 6-12") for over 5 minutes while a tech harnessed to the
> side and hanging down attaches the insulator on top of the tower in 30 mph wind.

Hovering with respect to the ground in a 30mph wind is the same as moving 30mph in still air.

Re:sturdy? as opposed to a helicopter?

[Profane MuthaFucka]

What kind of helecopter was it? And how long did he have to hover there? And did his boss care that he was burning fuel at an amazing rate to get the job done?

Probably not. The boss probably wants him to burn the gas to the get the job done. On the other hand, the news chopper won't hover in a stationary position because he can save a shitload of gas by moving forwards a little bit. If he's in a jet copter, he'll have the power to do what he wants. But he might not want to burn the extra gas. If he's in a Robinson, his options are more limited for high altitude hover.

Penguin on a treadmill

[electrofreak]

I like the story about penguins on a treadmill more.

Excellent!

[Vexor]

Now we have our own device to abduct aliens from their homeworlds.

Re:Excellent!

[Farmer Tim]

Why would we want to do that?

Revenge probing?

Coand effect

[Manhigh]

Aren't pretty much all low-speed aerodynamics based on this? Isn't this pretty similar to the Kutta Condition? (Air tends to leave a sharp edge parallel to that edge).

If air didn't stick to smooth leading edges, aircraft could never get enough L/D to fly subsonic.

Re:Coand effect

[Red Flayer]

No. The Coanda effect is different than regular wing aerodynamics. The Coanda fallacy, the first external link on the coanda effect wikipedia article, explains the differences.

Re:Coand effect

[barakn]

It's interesting that you bring that first link up. The second link, Coanda Effect: Understanding Why Wings Work, is from no less than Jef Raskin, the father of the Mac. It contains a fallacious argument on why the Bernoulli effect can't explain the lift generated by a wing, which he claims he first derived as a child. It contains some child-like assumptions, the most grievous being the assumption that the ratio of the chord lengths (distance over the wing versus under the wing) is the same ratio as the speed of the air over the wing versus under. This implies that two air molecules that separate at the front of the wing, one going over and one going under, will meet at the back edge of the wing, as if joined by some invisible rubber band. In reality the ratio of the speeds is larger than the ratio of the chords, and the top molecule reaches the back long before the bottom one does. This link to a different page on the same website as the first Coanda fallacy link, shows the airflow using smoke pulses and does a great job of describing what is going on.

My one question

[rehtonAesoohC]

Disclaimer: I'm not aeronautical engineer, but...

I'm curious whether the flying saucer would be stable and not spin around. Helicopters have rear rotors so they can counteract the spin forces induced by the main rotor. Other helicopters have two rotor blades on top of each other, one spinning one way, the other spinning the other way.

Without a design that counteracts the torque caused by the only rotor, what is it that will prevent the UFO thing from spinning around like crazy?

Re:My one question

[Anonymous Coward]

I'm an aerospace engineering student.

Note the scoops on the sides. They're all directing the airflow clockwise (as seen from top). If your rotor is also spinning clockwise (as seen from top), the airframe will be torqued counterclockwise, and those little scoops will counter the torque.

Just my guess.

Re:My one question

[RegularFry]

Observe the channelling fins around the edge along each side. They aren't quite vertical. My guess is that the angular velocity they impart balances the torque of the rotor.

Re:My one question

[Rogerborg]

There's a little goblin inside who spins it the other way.

Not funny, not informative, but at least it's not another dupe.

Re:My one question

[BostonPilot]

There are two different mechanisms used to yaw a helicopter, depending on whether we are talking about in forward flight, or in a hover.

In forward flight, the main rotor thrust is tilted which pulls the helicopter to the side. As the helicopter moves to the side, the vertical fin at the rear of the helicopter provides weathercock stability, much like the fins on an arrow. This yaws the helicopter in the pro-turn direction. Some helicopters need a little bit of pro-turn anti-torque pedal, but this is a minor correction to keep the aircraft in trim. Most of the yawing force in forward flight is being provided by the (fixed) vertical stabilizer.

In a HOVER, a conventional helicopter uses tail rotor thrust to yaw the aircraft. As a previous poster pointed out, this is done by changing the angle of attack of the tail rotor, not by changing the speed. As he pointed out, in full size helicopters, the main rotor and the tail rotor are connected by drive shafts and transmissions, meaning their speed is always at a fixed relationship to each other. This is done so that during unpowered flight (autorotation) the main rotor can keep the tail rotor turning, to give the pilot yaw control during the glide and landing.

Also, you are incorrect about how counter-rotating helicopters generate yaw forces. A tandem rotor helicopter like the CH-46 and CH-47 generate yaw forces by tiling the front and rear rotors in opposite directions. To yaw left, the front rotor is tilted to the left, and the rear rotor is tilted to the right. Coaxial and intermeshing helicopters generate yaw forces by changing the relative pitch of the rotors. This causes the rotor turning in one direction to generate an increased torque force, while the rotor turning in the opposite direction generates decreased torque forces. The imbalance causes a yawing force. Note that these systems need to work backwards when in autorotation. I've never flown one of those systems, so I only know what I've read - someone who has flight experience in a Kaman or Kamov might comment?

Back to the particular device in the article, the anti-torque force seems to be generated by a combination of fixed fins around the circumference (note how they are all bent in the anti-torque direction) and the (4?) moving fins which are probably there to provide yaw control to the operator.

Hmmm...

[ProteusQ]

It just won't seem real to me until it fires laserbeams from its undercarriage at passing motorists and pedestrians while the words "De-stroy! De-stroy!" are chanted from its external loudspeaker system. If its targets all looked 50's retro, that would help too.

Amazing opportunity...

[cno3]

For a new breed of modern warfare. Simply fill the device with eels...

Re:Amazing opportunity...

[LouisZepher]

I will not buy this record, it is scratched...

Re:Maintenance?

[the_wishbone]

FTA:

"'Unlike a helicopter, though, this is aerodynamically neutral and you can bump into walls and not smash the rotor,' said the inventor.

"And, unlike a hovercraft, you can fly it as high as you want.'

The dome-shaped object is powered by an electricity-driven propeller on top that pushes air over the outer surfaces, and has controllable flaps.
Geoff's Flying Saucers - the original name for his GFS Projects company - are based on an aerodynamic principle that has been around for nearly 100 years.

Known as the Coanda Effect, after a Romanian jet-engine pioneer, the principle is today used primarily in helicopters that have no tail rotors."

Sounds to me like it's even less complicated than a traditional helicopter. The blades in a traditional helicopter go through some incredibly complex motion. From the pictures in TFA, it looks to me like this is a simple propeller. Rather than relying on complicated mechanisms on the blades, it exploits the properties of the working fluid (air in this case). The adjustable flaps over that outer surface look simple enough.

Seems to me like a lot less complex, mechanically, than the helicopters we've been deploying to wars for decades.

seems inefficient?

[llZENll]

How is forcing the airflow over the body of the aircraft itself an improvment over an open airpath directly through the craft (a hole)?

Re:seems inefficient?

[Rogerborg]

It's far more efficient than a helicopter. It's getting lift both from the airflow over the rotating blades, and from the flow of the downwash over the body. In a traditional helicopter, most of that downwash is simply wasted.

Re:seems inefficient?

[jhfry]

Hovercraft's that use the technique you describe would be required to move a lot more air, and do not do so well at higher altitudes where the air is thinner. This is due to their lift being generated entirely by creating a low pressure zone above the craft by moving huge quantities of air from one side of the craft to the other.

This craft moves a smaller amount of air across it's surface, like the wing of an airplane, the way the air flows across it's surface creates the low pressure zone necessary to create lift.

The method you discuss, works well in situations where the rotors are very large in relation to the body of the craft, while this method works even when the rotors are much smaller in relation.

I am sure someone with a little more understanding of the physics involved could improve upon what I just said, but I'm pretty sure this is the way it works.

Look at those curved fins on the sides.

[porkchop_d_clown]

I bet they direct the thrust to counteract the torque of the motor.

From the video, it appears

[GungaDan]

that the military is only interested in surveillance of VERY LOUD PEOPLE. That thing shrieks...

What to call it?

[Tickenest]

I think hovercopter beats helicraft, but that's just me.

More of a flying hovercraft, not a helicopter

[Radon360]

If you look at the main "lift generating mechanism," it is essentially a fan/turbine, not a wing. As such, it generates its lift by forcing air downwards, developing thrust. A helicopter's main rotors are shaped liked wings (airfoil) on a fixed-wing aircraft. As such, the wing develops lift by forcing the majority of the air over the top of it to create an area of low pressure over the top of it as it rotates.

While its flight my appear to behave like a helicopter, it is not working on the same principles of flight that a helicopter uses.

Re:More of a flying hovercraft, not a helicopter

[Anonymous Coward]

Close, but not quite right. Im being picky here, but IAAAE (i am an aerospace engineer) and it bugs me to see all the incorrect definitions of lift.

The main lift mechanism for this vehicle is the Coanda effect. The acceleration of the fluid as it curves around the body of the "ufo" generates the majority of the lift. The fluid curves because it is a viscous fluid and experiences boundary layer attachment, ie there is friction between the fluid and the surface which keeps it "attached" to the convex shape. I assure you that the thrust generated by his tiny propeller is not nearly enough to lift the vehicle vertically by itself.

"As such, the wing develops lift by forcing the majority of the air over the top of it to create an area of low pressure over the top of it as it rotates."

There is no majority or minority of flow over an airfoil. In fact, boundary conditions for the freestream are generally positive and negative infinity. If lift was only generated by more flow going over the top, airplanes would have a really hard time flying inverted!

Lift is indeed generated by the integration of an asymmetric pressure distribution, but the interesting thing is what causes the asymmetric pressure distribution. Simplified a bit, lift is a reactionary force on the wing, generated by the downward change in momentum imparted to the fluid due to the airfoil's shape.

Or you can explain lift with circulation theory, which is a mathematical model that makes no practical sense to anyone :)

Re:More of a flying hovercraft, not a helicopter

[Radon360]

Desite your reply as an AC, I have to give you credit for correcting me on this one. You pointed out something that I did miss. I did recognize that the Coanda effect was redirecting the airflow downward around the edges (I have air knives here at work that do this), but missed that the air movement over the surface would also generate a lifting force as well.

Re:Maintenance?

[jandrese]

That's because it isn't new. The Avrocar was using a very similar system in the early 60s. While I'm sure the scale model pictured in the article has no trouble going up or down, I bet it has a lot of difficulty building up linear velocity while maintaining stability. That has always been the trouble with these aircraft. They're great if you only want to go up or down, but most people want lateral movement as well.

As an aside, I'm not sure why using the Coanada effect is better than just building a ducted fan with internal control surfaces. Putting that big blockage in your airflow just seems like it's going to sap power from your engine.

Re:Why is this a great idea?

[fiannaFailMan]

This thing has to carry heavy batteries or fuel, limiting its range. And it's ungodly loud. A small dirigible is silent and I imagine you can make one pretty small given how lightweight today's surveillance tech is.

Sounds like a great argument against helicopters too.

Re:Maintenance?

[posterlogo]

Slashdot tip of the day : Tags are not comments, they're ment to help people search for topics. Write a comment or leave

Actually, half the tags come across as heavily opinionated comments. Questions are answered "yes" or "no" or often, both. A product that might not work quite right or a company that gets its come-uppens gets tagged "haha".

Ya, these are really going to help anyone search.

"Wright Brothers"

[mattr]

Interesting how they mentioned this is like the Wright Brothers in terms of being very early in its development.

It sounds like it could work underwater maybe.

It looks like it is made for silicon wafer size engineering, microdrones.

I wonder about the linear speed and turning too. Would it be bad to put wings on it? Is that just a propellor and not a turbine like in the Avrocar? Would a turbine be better, and would tilting it naturally turn the machine's direction through gyroscopic precession?

If you put a rocket on one side, would it stay stable?

Could some kind of electrostatics (perhaps wires suspended above the disk parallel to it) help increase air flow by physically drawing it past the surface? Thinking of the "lifter" models.

If it was rising through a charged fluid you might think it could be leveraged. Usable in high atmosphere?

Is its rate of rise limited by the weight of the cowling it needs as a surface?

Does it use rare earth magnets like in engines inside electric car wheels?

Would a spiral ramp-shaped body like Da Vinci's early helicopter design actually work with a fan on top?

Would another fan help in maintaining stability and speed direction changes, like with helicopters tail blades?

Re:Maintenance?

[mhall119]

If your RTWA (Read the Wikipedia Article) you'll learn that the "blockage" isn't at all a blockage, and the air blown down by the fan runs along the side and then straight down, instead of being deflected back up, which means there is no "sapping" of power. This gives you the entire center cavity for payload, instead of making it a hollow cylinder like a ducted fan would require.

Re:Maintenance?

[jandrese]

Yeah, but physics says that if your airflow is being redirected it's not only losing power from changing the direction of the flow, but also from friction between the airflow and your surface.

Re:Frisbee

[mh1997]

It looks like it turned into this http://www.defensetech.org/archives/002723.html

Re:Sturdy vs surveilance helicopters, perhaps

[djdavetrouble]

So what you are saying is that we need to build a new super shotgun that shoots wet wads of toilet paper ? ;)

Re:DIY rc coanda effect saucer (with plans)

[Anonymous Coward]

What's really amazing is that the company you mentioned that already invented this (gfsprojects) was founded by someone *with the same name* as the person who invented that which is mentioned in the article. What are the odds? Staggering! Staggering I say!

Being laughed at is not a guarantee of success

[Chemisor]

They laughed at the Wright brothers. They laughed at Torvalds. But they also laughed at Bozo the clown.

I'll believe it when

[Flying pig]

it's in something more respectable than the Daily Mail. For the uninitiated US-ers, the Daily Mail is the UK equivalent of those US magazines with articles like 'aliens abducted my sister'. It pretends to be a newspaper but it is woefully, embarrassingly bad and its articles, to put it extremely politely, would mostly not survive the NYT fact-checking process. Assume, therefore, that this story is over-hyped. The US military has a habit of acquiring any potential military application "just in case" it comes good. Unless there is a huge pork barrel project available, that may well be where it stops. No-one else can legally acquire the technology and they can add it on to the annual list of exciting R&D projects to show everybody is earning their pay.

The only thing in the inventor's favour is that the British MOD has a track record of failing to recognise useful inventions (such as RSA encryption, which it had long before R,S and A and ignored) while spending a fortune on torpedoes that don't work, nuclear submarines with no role, tanks with undersized engines, and rifles that don't shoot properly. For long haired left leaning peaceniks like myself half the charm of the MOD is its ability to reduce the risk that we will get involved in a major war by making sure our armed forces are ill equipped to fight one. (that was sarcasm btw). However, my own view is that they regard flying surveillance vehicles as unnecessary. The plan is to cover the entire planet in talking CCTV cameras, which will probably catch speeding motorists as well.

Re:Maintenance?

[radtea]

Yeah, but physics says that if your airflow is being redirected it's not only losing power from changing the direction of the flow

Fluids is a tricky subject, and not just grammatically. So long as the force doing the redirecting of the flow is everywhere normal to the direction of the flow there is no power expended in the process of redirection. This is not quite the case in the Coaanda effect, which seems to be mediated by frictional effects, but one of the startling things about it is that the normal forces are much larger than the frictional forces, so you do get substantial redirection with very small losses.

Re:Maintenance?

[budgenator]

If you want to know how to get around the rotor stall problem, you have to look to the masters of rotory wing flight, the Russians. The Russian answer is contra-rotating wing, each side has equal lift and the additional benefit is you get to have two Jesus nuts instead of one. The Jesus nut is the nut that holds the rotor shaft on, if the Jesus nut falls off all you can do is say "Oh Jesus"

Did the military forget they tried this already?

[CXI]

Linked from the Wikipedia article in the summary is the Avrocar: http://en.wikipedia.org/wiki/Avrocar_(aircraft)

That's a full scale model of the very same technology! I imagine in this day and age of computer control it will be more successful, especially as a UAV, but how can this guy get a patent on technology from 1958 and claim it as new?

Plans for building your own

[wrmrxxx]

There are plans to build your own version of this aircraft here, along with quite a few videos of it in flight. I'm amazed by how stable and under control it looks in the video of it flying outdoors in a wind.

Re:Who was first? (with video)

[nireus]

If you had checked at the end of the page and http://jlnlabs.imars.com/gfsuav/gfsuav.htm you would had seen that the guy is giving credit to Hatton and gives a brief history of machines based on the same physics.

Better structure for lift and control

[Ungrounded Lightning]

... the "blockage" isn't at all a blockage, ... there is no "sapping" of power. This gives you the entire center cavity for payload, instead of making it a hollow cylinder like a ducted fan would require.

It also causes the lift (and thrust) to appear distributed over the surface of the fuselage (except for the very center), where it can be easily transferred to support the payload.

With a helicopter lift appears on the rotor. It must first be focussed on the rotor shaft, then passed through a bearing, and finally distributed to the airframe via a skeleton that is hung from the bearing. Here there is a local tug-of-war between the rotor and the center of the fuselage, then the lift appears in a ring around it.

Same idea as the "flying wing". Or Bucky Fuller's "all the strength is distributed through the skin" geodesic designs, with their fantastic strength-to-weight ratios.

Also:
  - The system is more stable with the lift appearing in the outer regions rather than at the center.
  - With a broad lifting surface (like an airplane wing) more ordinary control surfaces can manage the craft's flight - or you can modulate the lift in patches by valving in air leaks to selectively break the airstream attachment.
  - In a helicopter much of the control is done by dynamically adjusting the pitch of the blades using a complicated control structure and shafts in bearings that constantly dither once per rotor rotation - then the forces must be transferred by applying bending stress to the rotor shaft! With the coanda saucer the blades are a solid structure that only creates an airflow, while the control structures only move when the control parameters change.
  - Unlike a helicopter, lift can be adjusted to trim out major offsets of the load's center of gravity.