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Hybrid RotorWing Design Transitions From Fixed To Rotary Wing Mid-Flight
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."
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.
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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.
10 PRINT CHR$(205.5+RND(1)); : GOTO 10
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 rather than teardrop-shaped like a typical NACA airfoil. 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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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. The Harrier uses a jet engine and ducting to direct the jet blast downward. There are no tilting rotors.
Even those who arrange and design shrubberies are under considerable economic stress at this period in history.
Yep, I remember this too. I even found the site of someone who claims to have created it. But you and he are off by 10 years - it was July 1987.
(T>t && O(n)--) == sqrt(666)
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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