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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."
How many of those helicopters that are still flying were flown a wall at any point during their service life?
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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).
Now we have our own device to abduct aliens from their homeworlds.
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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.
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.
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.
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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
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.
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