Hybrid RotorWing Design Transitions From Fixed To Rotary Wing Mid-Flight 86
cylonlover writes "Attempts to combine the vertical take-off and landing (VTOL) capabilities of a helicopter with the high-speed flight and long range capabilities of a fixed-wing aircraft have been tackled in a number of different ways – from tiltrotor designs, such as the V-280 Valor and Project Zero, to fixed rotor aircraft that transition from vertical to horizontal flight, such as the SkyTote and Flexrotor. Australian company StopRotor Technology has taken a different approach with its Hybrid RotorWing design concept which features a main rotor that switches from fixed rotor to fixed wing in mid air."
Harrier? (Score:2)
Is this like the Harrier, where the motor switches from vertical to horizontal?
Re:Harrier? (Score:5, Informative)
A bit different. The rough rotor equivalent of the Harrier is a tiltrotor design, where the rotor rotates from a position where it generates vertical thrust (for takeoff) to one where it generates horizontal thrust (for flight).
This design instead stops the rotor when in horizontal flight, fixing it at an angle perpendicular to the fuselage so it becomes a wing generating lift. Then forward thrust is provided by separate, flight-only engines mounted in a conventional manner. When the plane wants to land again, the rotor stops being a wing, and starts spinning again in a helicopter style, to provide vertical thrust.
Re:Harrier? (Score:5, Informative)
A bit different. The rough rotor equivalent of the Harrier is a tiltrotor design, where the rotor rotates from a position where it generates vertical thrust (for takeoff) to one where it generates horizontal thrust (for flight).
You are thinking of the V-22 Osprey. [wikipedia.org] The Harrier uses a jet engine and ducting to direct the jet blast downward. There are no tilting rotors.
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I think his original comment made it clear he knows the difference; that's why he called the Tiltrotor a 'rotor equivalent to' the Harrier.
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The rough rotor equivalent
Me thinks you fail to grasp simple english... :p
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Actually, it does *NOT* stop the rotor in horizontal flight. They put it into a controlled fall and use that period to transition the airfoils.
For that reason, I don't think it will "fly" as a passenger vehicle. Maybe for larger drones, but I've met few people who like a fall during their commute.
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It still has wings so maybe it just descends while the rotors transition.
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When a harrier does this so well, why would you want to make a rotor equivalent? Is there a problem, or do they want a plane that can operate like a helicopter (be nimble, hover at will, move sideways) for one occasion, but then change to a fighter for another occasion?
Is the goal just a new form of VTOL, or is it expected to operate in both settings?
Re:Harrier? (Score:5, Informative)
Is this like the Harrier, where the motor switches from vertical to horizontal?
No, it is a helicopter where you stop the rotor and then use it as a wing for flying straight ahead with a traditional propellor. There is a typo in the summary.
This design would necessitate that the airfoil be symetrical along the long axis. Think VW Beatle shaped [wikipedia.org] rather than teardrop-shaped like a typical NACA airfoil [wikipedia.org]. This is probably a lot less efficient than a normal airfoil. Locking the airfoil would also be tricky- The rotor must come to a stop, so upwards lift is basically 0. At the same time, there is no wing for the front propeller to work on. Or worse, a wing oriented in the wrong direction. If they make a full-scale version, I hope the test pilot is single without any kids.
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According to the article, it engages in a free fall to provide it with the time it needs to stop the rotor and lock it in place as a wing, as well as to procure the air speed it needs to have upward lift. As you said, I hope the test pilot has no family.
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I think this looks like an ~excellent~ drone-only technology.
Re:Harrier? (Score:5, Interesting)
Been done. S-72 and X-50 prototypes. Its very unstable. The bring a rotor to a controlled stop thing is easy, existing rotor brakes can be geared to align it fairly precisely when it comes to a stop. The lift transition is the issue. It's not just that lift is basically 0. It's that one half of the rotor disc (the theoretical abstract describing the lift forces) has to completely reverse the airflow of the lifting surface.
Its essentially an expanded case of the Retreating Blade Stall problem.
But the retreating half of the rotor disc has to, as some point, go from generating lift from a retreating motion through the air (moving backwards relative to airframe, due to rotation) to generating lift from an advancing motion through the air (moving forwards, relative to airframem though no longer rotating). The easiest way to think about it isnt to think of it as going from rotating to fixed, but rather think about a rotor that is simply being reversed in direction (simplfies a lot of math).
So at some point in the middle there, half the rotor disc will fall below stall speed, and experience a stall similar to the effect of a Retreating Blade Stall. Worse, won't regain sufficient lift until its now going ~100 KIAS in the opposite direction. Think of it as stalling between -100 and +100 KIAS (example number) as it crosses the transition.
The only craft I can see being able to cross that boundary zone would be a very small, very lightweight rotor that is able to make extremely fast accelerations, and thus cross the zone before it's able to affect the craft much. A full scale craft would simply have too much inertia/momentum to be able to make the transition fast enough, without tearing itself to pieces. Likewise for any craft trying to stop the rotor and use forward motion to generate the lift.
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They have a way to get around the rotor stall issue. While none of the videos had a shot of a transition it looks like the aircraft stalls, ceasing forward movement, and while it is falling through the air the rotor spins up or spins down. The then use the conventional control surfaces to translate the vertical movement into horizontal movement. That could require quite a bit of a drop depending on how fast the rotor can change speed.
It looks like quite a carnival ride during transition..
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i saw the part where they add what basically seems like an autorotation transition to the mix. i didnt talk about that, simply the general idea and engineering problems of slowing/stopping a rotor in flight.
Autorotation itself is interesting because it's another transition of forces. Whereas autogyros use autorotation by default, at all times, a helo does not. a helo effectively (but not precisely, because airfoil lift is more complex than simple "fan pushes air") directs air downward, or stated another way
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The only craft I can see being able to cross that boundary zone would be a very small, very lightweight rotor that is able to make extremely fast accelerations, and thus cross the zone before it's able to affect the craft much. A full scale craft would simply have too much inertia/momentum to be able to make the transition fast enough, without tearing itself to pieces. Likewise for any craft trying to stop the rotor and use forward motion to generate the lift.
There is another solution. With coaxial rotors there's less of a stability problem because the lift can remain symmetric even if the retreating blades are completely unloaded. The Sikorsky X-2 (and S-97 Raider) use this configuration along with a pusher prop to achieve a 250 knot forward airspeed, but I don't think they drop the rotor speed all the way to zero.
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Right, and the S-69 before them, though it also never got to the point where they reduced rotor speed. Something about too much airframe stress. Slowing down the rotor would allow a higher forward speed with the same total force on the rotor, but the combined forces on the airframe as a whole, particularly in the support structure (rotor/body interface), could be an issue.
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I love the details! (Score:2)
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Hey, they have to leave room for the awesome crashing action that their pro-level competitors over at the V-22 project have been delivering so aggressively...
The 6th Day (Score:5, Funny)
Someone has been watching it.
"Convert to da choppa!" - Arnold Schwarzenegger
Though at least these guys seem to have worked out how to stop the thing from sinking like a stone during rotor transition though, which is a welcome feature.
Re:The 6th Day (Score:5, Informative)
Though at least these guys seem to have worked out how to stop the thing from sinking like a stone during rotor transition though, which is a welcome feature.
I don't know, the flight path from their simulation video looks a lot like it drops like a stone for a while:
1) Fly along in "airplane mode" with the rotor fixed perpendicular to the body, acting like a wing - regular amount of lift being generated
2) lift the nose until the airflow is perpendicular to the bottom of the rotor - not much lift being generated now
3) unlock the rotor so that the wind can start it rotating like an autogyro - starts to provide significant amount of lift
4) apply power to the rotor and get into helicopter mode - regular amount of lift being provided.
Step #2 looks a bit like falling.
Going the other way
1) Fly in helicopter mode, moving forward at a fast clip - regular amount of lift being provided
2) Lift the nose to get airflow perpendicular to the bottom of the rotor -
3) Stop the rotor and get it fixed perpendicular to the body - not much lift being generated now
4) drop the nose to get the airflow over the now fixed wing - regular amount of airplane lift.
Step #3 looks a whole lot like falling.
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D'oh, beaten. But they didn't work out how to stop it from diving during transition, the video shows it going into a huge stall when transitioning from fixed-wing to rotorcraft mode.
Re:The 6th Day (Score:4, Informative)
http://en.wikipedia.org/wiki/Sikorsky_S-72 [wikipedia.org]
It's just an autogyro (Score:1)
This is not a new concept. Autogyros are very old tech.
Re:It's just an autogyro (Score:4, Informative)
Autogyros are very old tech.
From TFA "The design features a powered main rotor" so no, not an autogyro.
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FTFA;
The Hybrid RotorWing can operate in five different flight modes.
Fixed Wing Flight: where the RotorWing is locked to operate as a fixed wing
Rotary Wing Flight: The RotorWing rotates like a helicopter rotor providing sustained hover capability
Compound Rotary Wing Flight: where the rotors requirement to produce lift and thrust is off loaded to other lifting surfaces or propulsion engines
Autogiro Flight: a form of rotary wing flight where the rotor is driven by the relative airflow and not directly by the
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I wonder if autogyro mode could be used to transition between fixed wing and helicopter-like flight without the huge stalls. The wing could be unlocked and a little power applied to start auto-rotation, then it would be a matter of metering in more rotor power and tail rotor thrust to transition to helicopter mode. Heli to fixed wing would be the reverse. I can't imagine autogyro mode is too useful when you have fixed wing mode...maybe good for short takeoffs and landings.
Not an autogyro [Re:It's just an autogyro] (Score:2)
The working prototype is a helicopter with an added prop on the front.
This is not a new concept. Autogyros are very old tech.
No, it's not. First, it's not an autogyro, although it apparently can operate in autogyro mode. But, more important, once it has forward motion, the rotor stops rotating and becomes a wing.
check some of the images here http://www.gizmag.com/hybrid-rotorwing-stop-rotor/27092/pictures [gizmag.com]
Smashed together a plane and heli (Score:1)
Man is that thing ugly (Score:3)
It's interesting engineering and all, but I was kind of hoping that when someone finally built a helicopter that transformed into an airplane, it'd look cooler. This thing looks like a flying cigar with toothpicks coming out of it. As it is I think I'd rather fly in that autogiro made of crates, whose rotor was Pippi Longstocking spinning a pair of brooms, than this thing.
Saw this in Popular Science 15 years ago... (Score:2)
Everything that's old is new again.
Saw this in Popular Science 25 years ago... (Score:5, Informative)
Yep, I remember this too. I even found the site of someone who claims to have created it. [nemontel.net] But you and he are off by 10 years - it was July 1987. [google.com]
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http://en.wikipedia.org/wiki/Sikorsky_S-72 [wikipedia.org]
The sikorsky S-72 demo prototype. Never actually made the conversion from rotary to fixed flight mid-air, but did fly in both configs seperately.
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they also followed on a few years ago with http://en.wikipedia.org/wiki/Boeing_X-50 [wikipedia.org]
It actually made the transition....or tried to. Both prototypes crashed.
Mattel to sue (Score:2)
In other news, Mattel to sue StopRotor for copying its various GI Joe and Cobra toys from the 80s
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Isn't GI Joe made by Hasbro?
Darn it, you're right. I get those old companies confused.
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Yes.
http://www.hasbro.com/gijoe/en_US/ [hasbro.com]
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Maybe the wing has no control surfaces. It could use control blending on the elevators and canards.
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It wouldn't have any control surfaces, nor would it need any.
Just like in normal rotary flight, you simply change the pitch of the rotor blade. The entire wing is an aileron, not any small portion.
The entire layout change consists of ... rotating the receeding rotor 180 degrees (if they even bother to do that) so that its shape is the most aerodynamic. You could just leave it and compensate for the additional drag and lower lift using other control surfaces if you wanted to reduce complexity and remove th
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If you think the V-22 shouldn't be flying you have no idea how incredibly hard to control the stealth aircraft are. A v-22 pilot actually flies his aircraft, no F-22, F-35, F-117, or B2 bomber would make it very far past the end of a runway if it wasn't for the computer that ACTUALLY flies the aircraft. The pilot just points the thing in a direction and the computer makes it happen. The V-22 has no where near that sort of fly-by-wire system. The V-22 as it was tested required the pilot to actually be in control of the aircraft, not just pointing it in a direction and letting the computer do the work.
It sounds like you haven't heard anything about the V-22 in a couple decades. The V-22 is extremely high-tech. It has a glass cockpit and triple-redundant fly-by-wire-system and is currently in Operational status and flying all the time. I watched a pair of them doing fast-roping exercises a few days ago.
New job? (Score:2)
I wasn't aware that Stephen Hawking was doing narration for videos.
What's a fixed rotor? (Score:2)
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Fixed, as opposed to tiltrotor. You know, like the summary says.
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A rotor that isn't a tiltrotor or mounted on a tiltwing?
Sure, usually you'd just say "rotor" but when talking about the domain where a tiltrotor is one of the most well known techniques they might have felt the need to make a distinction.
You mean... (Score:2)
They finally got the V22 Osprey to work?
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Try and keep up ;)
Who will try this thing? (Score:2)
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If I could certify it in X-Plane and make it fly, I'd hop in.
You don't actually think engineers go fly this aircraft with pilots who have no idea what its going to be like, do you?
Bell helicopters has pilots 'certified' for new aircraft before the aircraft has finished the production line. This isn't the 80s anymore man, we simulate before we do the real thing. Hell, even Space Ship One and Two pilots are certified on X-Plane before they go fly a brand new experimental orbital craft.
Is this a good solution (Score:2)
The rotors need a drive mechanism. This is dead weight when in level flight.
The rotors will need to be symmetrical, making them less efficient as wings and as rotors.
The whole system is more complex than either a plane or a helicopter. Makes building and maintaining it more expensive.
What are the advantages over a vectored thrust approach?
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Probably less fuel consumption, (if it works).
The only successful vectored thrust aircraft, the Harrier (in it's various guises), had severely-reduced range if its VTOL capabilities were used.
That (and loading considerations) mean that normal takeoff procedure was STOL, optionally using a ski-ramp.
http://en.wikipedia.org/wiki/AV-8_Harrier_II [wikipedia.org]
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You must be British. No one outside of Britain thinks the Harrier is a success.
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The rotors need a drive mechanism. This is dead weight when in level flight.
The turbine power plant would work in all phases of flight, this is trivial and already accomplished.
The rotors will need to be symmetrical, making them less efficient as wings and as rotors.
And? Most heli's already use symmetrical airfoils. Of course, the receding blade still needs to be rotated 180 degrees so its 100% efficient compared to rotary flight but its not a requirement.
The whole system is more complex than either a plane or a helicopter. Makes building and maintaining it more expensive.
Yes, but this has the potential to land at a hospital helipad, as well as go super sonic. We currently can not design helicopter rotors that are able to deal with sustained entry/exiting from supersonic speeds as it
Comfort much? (Score:2)
That said, I would NOT want to be a passenger in that thing! Even the computer model gets bounced around a hell of a lot during transition and that, I'd imagine, is modeled in calm weather. Not to mention, a lot of free-fall
The '80s called... (Score:3)
Will it beat the X2? (Score:2)
Sikorsky unofficially holds the record on fastest helicopter (the Sikorsky X2 [wikipedia.org]) which while not stopping the rotors, use them to generate a little lift for high-speed flight. It too uses a pusher prop and wings...
Stopped-rotor design new -- in 1976 (Score:2)
See the Sikorsky "X-Wing" modification of the S-72 RSRA [wikipedia.org].
What will be news is when someone builds something that goes beyond "concept" to "flyable aircraft that demonstrates in-flight transition between rotary- and fixed-wing flight.) But a stopped rotor concept is not much in the way of news.
Points of failure? (Score:2)
seems super practical (Score:2)
One of the videos shows the transitions between rotary and fixed phases, during which the vehicle is essentially in free-fall. How long does it have to stay in transition, spinning up/down the wing/blades before it can complete the transition? You can definitely rule passenger flight out, and will ikely be less reliable than the V-22 by an order of magnitude - and that's saying something.
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Yeah - that thing would have just about anybody puking and screaming for their mothers from the look of it. Sure, it might be safe in theory, but so is the vomit comet.
Airwolf (Score:2)
Isn't this what Airwolf did when it went supersonic?
Drone only (Score:2)