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Omnicopter
embodies attributes of Autogyro and Helicopter | |
The OmniCopter is a craft built with both a powerable tiltable flight rotor and a powered, steerable tail-propeller.
At low speeds/hover, the rotor is powered to provide lift and is positioned parallel to the body; the tail-rotor faces sidewards and is lightly powered to counter counter-rotation.
At
high speeds, the rotor is unpowered and tilted slightly backwards to act as a rotating "wing" while in forward flight; the tail-propeller faces backwards and provides forward thrust.
Transition from one mode to the other is smooth...
Heli to Gyro: (more) power is transferred from the rotor to the propellor while the rotor tilts slightly backwards and the propellor moves from sidewards to backwards.
Gyro to Heli: reverse of the above.
Note that precession from the propeller during transition balances the tilting of the rotor.
Gyroplanes are easier to fly long distances but helicopters have the neat "hovering" thing.
Article on hybrid aircraft
http://www.time.com...9171,821828,00.html
[phoenix, Oct 11 2008]
Co-axial rotor mast design
http://en.wikipedia...wiki/Coaxial_rotors
[UnaBubba, Oct 11 2008]
Pretty picture Sikorsky X2
http://news.cnet.co...84_3-9879588-7.html
[UnaBubba, Oct 11 2008]
Kamov Ka-50 pictures
http://images.googl...p&resnum=1&ct=title
[UnaBubba, Oct 11 2008]
Weiland Helicopters, developing commercial designs for sale
http://www.wielandhelitech.com/index.php
[UnaBubba, Oct 11 2008]
Fairey Rotodyne
http://en.wikipedia...iki/Fairey_Rotodyne
Close, but no cigar. [8th of 7, Oct 13 2008]
CH-45 Heliplane
http://www.cartercopters.com/ch-45.html
Very similar concept. Not yet built [scad mientist, Oct 13 2008]
[link]
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"Why bother ? gyroplanes are easier to fly long distances but helicopters have the neat "hovering" thing."
What's so difficult about flying helicopters long distance? |
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helicopters are more finicky than autogyros; their strength is in hovering... the OmniCopter combines some of the strengths and minimizes some of the weaknesses of both designs.
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I'm not sure I'd call it a "hybrid": the controls are pretty continuous in any speed range; the only discontinuity is when you switch from powered to unpowered rotor. |
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I don't actually see any relevance in the 1951 Time article linked though I am familiar with quite a few "convertiplane" designs. |
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You can resolve your stability issues with a coaxial rotor shaft system (two rotary wings, counterrotating on a single shaft). You can still have a tail rotor, if you want to use one as a "pusher" propellor. It also delivers much greater energy efficiency. About 25% of available poser produced by a helicopter goes to driving the tail rotor. |
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Coaxial rotor design also eliminates torque rotation effects, which is why you have the tail rotor on single rotor helicopters. Steering becomes very easy, using a single control column to vary blade pitch with precision. |
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[UB] got a link for an auto-rotating coaxial design ? |
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They eliminate the need for swashplates, cyclic and collective control, so there are no pedals to co-ordinate with stick control, either. |
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Kamov does a number of autorotating coax designs. I'll try to find a link. |
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I'd think you'd need more complex control (at least on the shaft if not in the cockpit)... thing is, if a coaxial rotor design helicopter runs out of gas it turns into a brick. |
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To my understanding it involves a far simpler set of controls. Just the joystick, with full XY movement range, to do the lot. |
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Autoratation issues were largely solved in the mid-50s as I recall from a TV show I saw a few years ago, with the invention of "tip brakes" (movable brake flaps mounted on the tips of the rotor blades). They allow the operator to deliberately slow the rotors' rate of turn in the event of a powerdown situation, allowing enough control to get the aircraft back to the ground reasonably safely. |
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I've emailed Weiland, to find what they have to say on the autoratation issue. They should contact me tomorrow. |
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You could be (probably are) right about co-axial rotor helicopters being able to auto-rotate to ground safely; not sure where I heard you couldn't.
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But my design is for a craft that embodies some of the features of both helicopter and autogyro in an aircraft that is hopefully not more complex than either one.
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Empennage would be smaller because steering is done by moving the tail-prop around. The rotor wouldn't have to be tilted very far back because you'd be flying low speed in "thrusted copter" mode. |
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[edit] okay this is just annoying, *none* of the links have anything to do with they idea.
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PS. y'all missed the "Curtiss X-19" which is *my* favorite convertiplane and also has nothing to do with this post. |
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I've "got" your idea. I simply posted links that have to do with coax mast designs. |
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...which would be more inefficent in forward travel than a one-rotor autogyro. |
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The hybrid aircraft link was a general overview of the concept for those not in the know. I was going to link to the Osprey and a gyrocopter too... You can delete the link(s) if you don't like it/them. |
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I'm guessing the steerable tail prop is going to unworkable, with the driven/undriven rotor a close second. I certainly could be wrong. |
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([UnaBubba]: That Sikorsky is a pretty bird) |
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The aircraft world certainly seems to be bereft of steerable engines, unlike say the outboard-motor world
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The main rotor though: you'd be in powered flight for low-medium speeds, forward velocity obtained by the tail-prop (unlike a helicopter which goes forward by tilting the rotor or the entire craft forward), so when you switched to high-speed mode (unpowered rotor) you wouldn't need to tilt the rotor back too much (unlike an autogyro at the low end of it's speed envelope) which also means that your tail boom won't get hit. I'm not getting into powertrain choices in the post, but obvious ones are driveshaft or electric.
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I *suppose* you could keep the rotor tilted backwards slightly and put an overly large fin behind a fixed pusher propeller. That would enable you to achieve equilibrium by virtue of the tail assembly both countering the rotor-rotation and backwards motion induced by the rotor. |
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Re: the piccies, I like aircraft piccies. |
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// I've emailed Weiland // |
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Ask them how the Yutani merger is going. |
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I don't think they'd get the joke. I can try. |
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"The Fairey Rotodyne was a British compound gyroplane ........ featured a jet-tipped powered rotor. Although promising in concept and entirely successful in trials, the Rotodyne program was eventually cancelled when a combination of politics and the lack of commercial orders doomed the project." |
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Sic transit gloria mundi. |
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They had it in mind for downtown city<>city transport, but it was incredibly loud.
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Size factor I had in mind for this thing was more in the ultralight region. |
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Great idea. It's very similar to the CH-45 Heliplane concept that CarterCopters proposed [link]. The main difference I see is that rather than a swiveling propeller they simply propose two adjustable pitch propellers that can counteract the torque and/or provide forward motion. They also have small wings for use during high speed cruise, so their model transitions from helicopter to autogyro to airplane. |
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Anyone intersted in this topic would find their web page quite interesting. They've got logs of their progress over the last decade. |
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