Abstract:
A rotary-wing apparatus that is aeronautically stable, easy to fly with a multidimensional control, small size, and safe to fly and low cost to produce. The rotary-wing apparatus includes a coaxial, counter rotating rotor drive providing lifting power with an inherent aeronautical stability; auxiliary propellers that face the direction of flight and are located on opposite sides of said coaxial rotary-wing apparatus and enable flying forwards, backwards and perform yawing. The rotary-wing coaxial helicopter toy is remotely controlled and safe to fly in doors and out doors, while performing exciting maneuvers even by untrained kids.

Description:
RELATED APPLICATIONS 
     This application is based on provisional application No. U.S. 60/624,941, filed on Nov. 5, 2004. 
     FIELD OF THE INVENTION 
     The present invention relates to flying apparatuses generally and more specifically to self-stabilizing rotating flying toys. 
     BACKGROUND OF THE INVENTION 
     The passion of flying has accompanied human beings from the early days of the humankind. The well-documented Helical Air Screw drawing of Leonardo Da Vinci in the fifteen-century was an important step towards a vertical take off, hovering and landing flying apparatus. It was only when a light weight powerful enough engine for powering rotating blades become available when Paul Cornu took off vertically in 1907. Vertical flights became easier and smoother when gyro control became available in mid-1940&#39;s and became common about a decade later. 
     A helicopter typically has two rotor blades that are connected through a drive shaft to an engine. The air deflected downwards due to the spinning of the rotor blades provides the lilting power. Rotor blades at the tail of the helicopter are directed in the horizontal plane to provide the anti-torque power that is required in order to prevent the helicopter from rotating due to the spinning main rotor. Changing the main rotor blades attack angle provides horizontal motion according to pilot&#39;s commands. 
     Sikorsky and Kamov first introduced a helicopter with two counter rotating main rotors on a common axis. Eliminating the need for tail rotor blades, the counter-rotating blades provide higher maneuverability and stability. 
     Flying toys history is even longer than that of flying vehicles. Unlike flying vehicles, flying toys are typically very price-sensitive. They should be stable, easy and safe to fly. 
     Consequently, Remote control flying toys should be designed to be inherently stable, with safe and durable structure and materials, using low cost components and very simple to manufacture. 
     SUMMARY OF THE INVENTION 
     The present invention provides an innovative rotary-wing apparatus that is aeronautically stable, easy to fly and control, very small in size, safe to fly and low cost to produce. In accordance with the present invention a rotary-wing flying apparatus innovative design eliminates the need for gyros and motion sensors, expensive actuators and movable parts, rotor blades with changeable attacking angle, nor a tail rotor. Consequently making it possible to be produced at a very low cost, thus enabling implementations such as toys and other low cost applications. In addition it consists of innovative safety features for the operator and its surroundings making it possible to fly a rotary-wing platform of the current invention even in doors. 
     Rotary-wing vehicle systems are well known and are being widely used for various mobile applications. The present invention diminishes at least some of the disadvantages associated with methods and solutions of very small helicopters that are designed for stability while maintaining minimal costs, a simple control, a high reliability, robustness and endurance and with no, or minimal need for tuning and adjustments. 
     In accordance with one aspect of the present invention, there is provided, a coaxial rotary-wing apparatus comprising: at least two sets of lifting blades connected to a main coaxial drive shaft; primary drive means connected to the coaxial drive shaft for driving the at least two sets of lifting blades at the same angular velocity, a first set of the lifting blades being driven by the drive means in a first direction of rotation, and a second set of the lifting blades being driven by the drive means in a second direction of rotation opposite to the first direction; the at least two sets of lifting blades being located one above the other, wherein the center of gravity of the coaxial rotary-wing apparatus is positioned lower than the at least two sets of lifting blades; auxiliary drive means, for driving the coaxial rotary-wing apparatus in at least forwards and backwards directions and for causing the rotary-wing apparatus to perform yawing motions; and control means for controlling the primary and auxiliary drive means. 
     In another embodiment of the present invention, a coaxial counter rotating rotor drive is used, providing inherent aeronautical stability. 
     In another embodiment of the present invention, a differential steering provides excellent yaw control, as well as forward/backwards control of the rotary-wing vehicle. A “tank-like” differential steering enables very convenient control of maneuvers even by the layman operator. 
     It would be appreciated that the inherent design of the blades system of the present invention eliminates the need of using expensive gyros, servos and pitch control means for maintaining flying stability. 
     In another embodiment of the present invention, using flexible blades with a “rigid type” rotor head for the rotary-wing vehicle provides smooth flying characteristics. 
     In another embodiment of the present invention, swept forward blades increase flight stability. 
     In another embodiment of the present invention, a flying vehicle flexible structure is provided, which absorbs the hit energy through a spring like structure of its body. 
     In another embodiment of the present invention, a blades connection apparatus enables blades to fold back in case of encountering excessive external force. It would be appreciated that the present invention enables exchanging of the blades without screws, or the need for tools. 
     In another embodiment of the present invention, blades tuning means is provided, which enables collective pitch tuning of a set of rotors using a single button. It would be appreciated that a single knob adjustment enables even lay people to intuitively adjust blades in case a yaw adjusting is needed for holding the rotary-wing flying apparatus direction while hovering or while flying and when no yaw control is externally provided. 
     It would be appreciated that the rotary-wing flying apparatus of the present invention may be remotely control by an operator. 
     Yet another embodiment of the present invention provides a manual adjustment of forward/backwards motion while in steady-state. A single button adjusts center of gravity of the rotary-wing flying apparatus to set preferred forward motion immediately after takeoff. It would also be appreciated that the center of gravity may be adjusted for forward motion without applying power to auxiliary differential power propellers, so the rotary-wing vehicle can fly forward in its steady state while saving energy, increasing flight time. Alternatively the center of gravity of the rotary-wing flying apparatus may be set for hovering in steady state and while no power is provided to the auxiliary differential power propellers. 
     Yet another embodiment of the present invention provides air brakes for stabilizing the rotary-wing flying apparatus in a forward flight. 
     Yet another embodiment of the present invention provides a tail fin for improved yaw stabilization. 
     Focusing on cost sensitive flying applications such as toys, cost of materials is very critical. Unlike other micro helicopters, such as the FR-II of Seiko Epson, which uses gyro-sensor, the current invention provides great flying stability without using gyro sensors, actuators, or a tail rotor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: 
         FIGS. 1 and 2  are simplified isometric views illustrating a preferred embodiment of the present invention, including a counter-rotating rotary-wing apparatus. 
         FIGS. 3A ,  3 B, and  3 C are isometric views illustrating a preferred method of connecting rotor blades of a rotary-wing apparatus. 
         FIGS. 4A ,  4 B,  4 C, and  4 D are exploded views of parts and assembly of the upper rotor head showing a yaw trimming control knob for a collective pitch change of the upper blades. 
         FIG. 5  is an isometric view illustrating an auxiliary power system for driving the rotary-wing apparatus forward/backwards/yaw. 
         FIGS. 6 and 7  are isometric views illustrating the main drive system of a rotary-wing vehicle. 
         FIGS. 8A and 8B  are diagrams illustrating swept forward blades of a rotary-wing vehicle. 
         FIG. 9  is a simplified illustration of rotors and stabilizing apparatus. 
         FIGS. 10A and 10B  are isometric views illustrating the air brakes apparatus for a better rotary-wing apparatus flying stabilization. 
         FIGS. 11A and 11B  are isometric views illustrating tail apparatuses and operation. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference is now made to  FIGS. 1 and 2  which are simplified pictorial diagrams illustrating one preferred embodiment of the present invention, a rotary-wing flying apparatus operating in a plurality of applications. The illustrated embodiment of  FIGS. 1 and 2  are presented in the context of flying toys, it is understood that this embodiment of the invention is not limited to toys and is equally applicable to other suitable types of small flying objects where cost, stability and ease of use are of importance. 
       FIG. 1  illustrates a front isometric view of a micro rotary-wing apparatus  10  of a preferred embodiment of the current invention. 
     A micro rotary-wing apparatus  10  consists of two sets of counter rotating blades, a lower rotor blades system  200  and the upper rotor blades system  100 . 
     A main coaxial drive shaft  300  provides a rotating power to the two sets of counter rotating blades  100 ,  200 . The main coaxial drive, shaft  300  consists of two parts: an outer main drive shaft  310  and an inner main drive shaft  312 . Outer main drive shaft  310  provides a rotating power to the lower set of blades  200 . Inner main drive shaft  312  provides a rotating power to the upper set of blades  100 . The two parts of main coaxial drive shaft  300  rotate at the same speed and in opposite directions. While the outer main drive shaft  310  rotates in one direction, the inner main drive shaft  312  rotates in the opposite direction. A counter rotating movement of the two sets of blades the upper set  100  and lower set  200  cancel each others angular torque. 
     The lower rotor blades system  200  consists of two blades  202  and  204 . The lower blades  202  and  204  are connected to the outer main coaxial drive shaft  310  using a rotor head  320 . 
     The upper rotor blades system  100  consists of two blades  102  and  104 . The upper blades  102  and  104  are connected to the inner main coaxial drive shaft  312  using a rotor head  350 . 
     Stabilizing apparatuses are connected to each of the two counter rotating blades systems  100 , 200 . A bell stabilizing apparatus  207  is connected to the lower blade system  200 . A bell stabilizing apparatus  107  is connected to the upper blade set  100 . 
     The two blade systems  100  and  200  provide lifting force for the rotary-wing apparatus  10 . 
     A main drive power assembly  500  that is shown in  FIG. 1  provides the rotating power to the two blade systems  100  and  200 , through main coaxial drive shaft  300 . 
     A main motor  501  provides rotating power through a main gear system  530  to main coaxial drive shaft  300 . A counter rotating power is provided by main gear system  530  to the main coaxial drive shaft  300 . The inner drive shaft  312  is powered in one direction while the outer drive shaft  310  is powered in the opposite direction. 
     An auxiliary motors system  400  of a preferred embodiment of the current invention consists of two sets of power assemblies, a left propeller system  410  and a right propeller system  440 . The auxiliary left and right propeller systems  410  and  440  provide forward, backwards and yaw movement of rotary-wing apparatus  10 . 
     It is yet another preferred embodiment of the current invention that the propellers of auxiliary motors system  400  are located above the center of gravity of the rotary-wing apparatus  10 . 
     A control unit  700  controls the operation of the rotary-wing vehicle  10 . Control unit  700  controls the operation of main drive power assembly  500  and the operation of auxiliary motors system  400 . Control assembly  700  may also have remote control capabilities and may also have processing unit and memory. Control assembly  700  may also consist of a receiver for receiving remote control commands. Such a receiver may be of radio frequency (RF), light such as infrared (IR), or sound such as ultra sound, or voice commands. Control assembly  700  may also consist of a pre programmed flying control, or programmable flying control to be programmed by the user. 
     A power assembly  600  provides power to all rotary-wing apparatus  10  driving and control units: main drive power assembly  500 , auxiliary motor system  400  and control unit  700 . Power assembly  600  may be such as a rechargeable battery, simple battery, capacitance device, super capacitor, micro power capsule, fuel cells, fuel or other micro power sources. 
     A remote control unit  900  may preferably be used by an operator to control rotary-wing vehicle  10  of current invention. Remote control unit  900  has throttle control  908 , which is preferably proportional control for controlling the power of the main drive assembly  500 , a left/right control  904  and forward/backwards control  906  for controlling the power and rotation direction of the auxiliary motor system  400 . Control for left/right and forward/reveres may be of proportional type or non-proportional type. The remote control unit  900  may also have a power switch  902 , an indicator  920  for various in actions such as power on/off, charging, battery status, etc. It may have a waves radiation transducer  960  such as RF antenna as shown in case RF is used for transmission of remote control commands. It may also have a charger output  950  for charging the power assembly  600  of micro rotary-wing apparatus  10 . 
     Skids  800 ,  810  may be attached to micro rotary-wing vehicle to enable it to land on various surfaces such as solid and liquid materials. The skids  800 ,  810  can be in various shapes and materials such as foam and or plastic. They are connected to the main body of rotary-wing vehicle  10  preferably with a springy structure such as the bars  802 ,  804 . 
     A canopy  12  as shown in  FIG. 1  may cover internal parts of the rotary-wing apparatus  10 . A preferred main body structure of the micro rotary-wing vehicle  10  is using a light material for the canopy  12 . An alternative main body structure would be using a foam structure for the canopy  12 , which would provide a compelling look of the rotary-wing apparatus  10 . The canopy  12  would preferably cover internal components of the rotary-wing apparatus  10  such as main driving assembly  500 . 
     In another preferred embodiment of the current invention, the rotary-wing apparatus  10  may also consists of a tail  870  for an improved directional stability. 
     In yet another preferred embodiment of current invention a rotary-wing apparatus  10  may also consist of air brake  850  that is preferably located below the center of gravity of rotary-wing apparatus  10 . 
     Reference now is made to  FIGS. 3A ,  3 B, and  3 C which provide illustrations of one preferred method for connecting rotor blades  202  and  204  of lower blade assembly  200  of rotary-wing apparatus  10 . In  FIG. 3A , a blade connector  203  is aligned with a locking pivot  224  of blades assembly  200 . Arrow  940  shows the direction of inserting a slot  205  of blade connector  203  onto locking pivot  224 . 
     Reference is now made to  FIG. 3B . Blade connector  203  is assembled onto blade locking pivot  224  of rotor lower head hub  212  of lower rotor head  320 . Blade  202  is now pulled away as shown by arrow  942  from the rotor assembly  212  so spring  234  now pushes blade connector  203  and causes a blade  202  to be held onto the locking pivot  224 . Arrow  944  shows the direction the operator needs to rotate blade  202 , so blade connector  203  will be locked into its fix fixed position with rotor lower head hub  212  of rotor head  320 . 
     Blade  202  is now manually rotated against spring  234 , as shown by Arrow  944 . Spring  234  slides over the blade connector  203  using the blade locking pivot  212  as its axis for rotation. Reference is now made to  FIG. 3C  where blade  102  is now in its “ready to fly” position. Positioning slot  240  of blade connector is held clicked in its position by Pin  225  and slot  240  and by the force of spring  134 . Locking other blades  204 ,  102  and  104  is implemented in a similar manner. 
     It will be appreciated that blades assembly apparatuses  100  and  200  of the current invention provide an innovative method that is simple to assemble and to replace blades even by a layman in the art of flying machines. Should a low external force be applied on blades  102 ,  104 ,  202 ,  204 , the blades will be swept back. By folding back a possible damage is avoided to an external object, or operator, which blades may hit. It would be appreciated that current invention method and mechanism of blades with folding capabilities, provide a high safety method and mechanism, so the probability of an operator of rotary-wing apparatus  10  of the current invention to be damaged by hitting the rotors is significantly lower. It would further be appreciated that the preferred rotor blades folding method of current invention also reduces probabilities for damaging blades  100 ,  200  themselves by hitting external object. 
     It would be appreciated that in order to increase safety of rotary-wing vehicle  10 , operator and other objects in the surroundings of rotary-wing vehicle  10 , blades  102 ,  104 ,  202 ,  204  will preferably be made from a soft and foldable material such as foam, flexible plastic materials, foils, or other soft, and flexible materials and that are strong enough to provide lifting power. 
     In another preferred embodiment, the invention control unit  700  of  FIG. 2  may also consist of means for detecting collision conditions. In case of a collision of blades  100 ,  200  with external objects, control unit  700  may detect the situation and stop the rotors rotation power. Such collision detection may be implemented by measuring a sudden increase of main motor  500  current, which is a result of an external force rather than a result of a user command for increasing throttle. 
     It would be appreciated that the method of connecting blades  100 ,  200  of the current invention enables fast and easy connection and disconnection of rotor blades  100 ,  200  from the rotor heads  320 ,  350  without fasteners and tools. 
     It would also be appreciated that the rotor blades are clickable into their position and therefore no further adjustments are needed. Another preferred embodiment of the current invention uses the same spring that holds the blade in its position so that it will not fold while the rotor accelerates, to enable blade folding in case the blade hits an external obstacle and provides additional safety. 
     It will be further appreciated that the present invention includes variations and modifications, which would function as fast connection of blades  100 ,  200  without the need of tools and a fast sweep back or blades disconnection due to operation of external force. 
     Reference is now made to  FIG. 4A , which is an exploded view of parts and assembly of upper rotor head  350 . A yaw trimming control knob  964  enables a collective pitch change of upper blades  102 ,  104 . Yaw trimming control knob  964  may have an internal thread. It can be manually turned by an operator of the rotary-wing apparatus  10 . Turning yaw trimming control knob  964  clockwise over contra bolt  954 , pushes collective control horn  960  downwards. Control horn  960  is connected to rotor head hub  930  using connecting pins  962 ,  964 . Consequently rotor head hub  930  is twisted. As a result, the pitch of rotor blades  102  and  104 , which are connected to rotor head hub  930 , is increased collectively. 
     Rotor head hub  930  is of a “rigid” type therefore it cannot titter; as a result the pitch axis of rotor head hub  930  is always kept perpendicular to main drive shaft  300 , enabling rotor forces to be transferred to main drive shaft  300 . 
     Rotor head hub  930  can freely rotate around pitch axis  952 , enabling bell assembly  107  to stabilize rotary-wing apparatus  10 . 
     Similarly turning yaw trimming control knob  964  counterclockwise over contra bolt  954 , pulls collective control horn  960  upwards thus reducing pitch angles of rotor blades  102  and  104 . 
     Upper rotor  100  rotates counterclockwise. By turning yaw trimming control knob  964  clockwise, the increased pitch of upper rotor blades  100  increases the moment that is transferred to the rotor hub  930  of upper rotor head  350 . The increased moment causes rotary-wing apparatus  10  to yaw clockwise. As a result, turning yaw trimming control knob  964  clockwise causes rotary-wing apparatus  10  to yaw clockwise. 
     The above-described yaw trimming method of the present invention enables an operator of rotary-wing apparatus  10  to prevent undesired yaw movements of rotary-wing apparatus,  10  while auxiliary motors  400  of  FIG. 1  are inactive. 
     Reference is now made to  FIG. 4B , which is an illustration of rotor head hub  930  of rotor head  350  of  FIG. 4A . Rotor head hub  930  consists of locking springs  932 , 934  that hold blades  102 ,  104  at the correct position; pitch control horn  940 ,  942  for receiving force of collective control horn  960  of  FIG. 4A ; flexible strips  936 ,  938 , which carry centrifugal forces of blades  102 ,  104  and also enable the change of angle between blades  102 ,  104 . Rotor head hub  930  can freely pivot around pitch axis  952  of  FIG. 4A  that is inserted though holes  948  of rotor head hub  930 . 
     Reference is now made to  FIG. 4C , which is an illustration of a partially assembled upper rotor head  350  and where contra bolt  954  can clearly be seen. 
     Reference is now made to  FIG. 4D , which is an illustration of a complete assembly of upper rotor head  350  and where yaw trimming control knob  964 , which enables a collective pitch change of upper blades  102 ,  104  is located at the top of upper rotor head  350 . 
     Reference is now made to  FIG. 5 , which describes yet another embodiment of the current invention. An auxiliary power system  400  consists of a left power assembly  410  and a right power assembly  440 . Each consists of a propeller and motor. Left power assembly  410  consists of a motor  412 , propeller  414  and protecting shield  416 . Right power assembly  440  consists of a motor  442 , propeller  418  and protecting shield  450 . 
     Propellers  414 ,  418  provide air thrust in a desired direction when spinning. Propellers  414 ,  418  can be rotated clockwise and anticlockwise independently and according to commands received from control assembly  700 . 
     Propellers  414 ,  418  are used to move rotary-wing apparatus  10  forward, backwards and in yaw (rotate horizontally clockwise or counterclockwise) movements. Auxiliary motors  412 ,  442  provide the rotation power of auxiliary propellers  414 ,  418 . Protective shields  410 ,  450  are used for protecting propellers  414 ,  418  and auxiliary motors  412 ,  442  against external damage and for safety reasons. Auxiliary motors  412 ,  442  are connected to the main rotary-wing vehicle&#39;s frame by means of flexible connecting rods  420 . 
     Another preferred embodiment of the current invention are auxiliary power systems  412 ,  442  that are located above the gravity center of rotary-wing vehicle  10  providing a correct pitching moment in addition to providing direct vector thrusts for directional control. It would be appreciated that preferred position of auxiliary power systems  412 ,  442  contribute to aeronautical stability of rotary-wing vehicle  10 . 
     Control unit  700  of  FIG. 2  controls the auxiliary motors  412 ,  442  movements. 
     Reference is now made to  FIGS. 6 and 7 , which describe main drive system  500  of rotary-wing vehicle  10 . Main rotary-wing vehicle drive system  500  consists of at least one driving motor  501  connected to a main gear system  530 . Main gear system  530  is also connected to main rotor drive shafts  300  of  FIG. 6  and of  FIG. 2 . A main gear system  530  consists of primary reduction gears  502 ,  504  and a counter rotating gear arrangement  511  consisting of gears  510 ,  512 ,  514  that are powered from primary reduction gears  502 ,  504  via an auxiliary drive shaft  508 . Gear  514  provides rotating power through drive shaft  312  in one rotating direction while gear  512  rotates drive shaft  310  at the same angular velocity and with an opposite direction. 
     It would appreciated that this embodiment of the current invention uses gearbox  530  to counter rotate coaxial main drive shafts  300 , and rotate upper and lower rotor assemblies  100 ,  200  at the same angular speed regardless of motor power. Consequently, the yaw of rotary-wing apparatus  10  of the current invention is not affected by changes in power of main motor  501 . It would also be appreciated that by suing the above-described embodiment of the current invention there is no need for additional active yaw stabilization means. No additional active stabilization means such as gyro sensors, servo systems, or additional motors enables reduction of the cost of producing the rotary-wing vehicle  10  to a consumer products cost level such as toys costs. As explained in  FIGS. 4A ,  4 B,  4 C, and  4 D, a simple one-control knob  964 , which is yet another embodiment of the current invention, enables tuning of a possible drifting yaw movement due to a residual difference in angular torque of upper and lower rotors systems  100  and  200 . 
     A power source tray  604  is connected to rotary-wing vehicle  10  via a flexible structure  606 . Power source  600  is held within the power source tray  604 . Power source  600  is preferably a rechargeable battery, or may also be a battery, a capacitor, a super capacitor, a fuel cell, small fuel engine, and other small-condenses power sources. 
     Referring now to  FIG. 7 , which shows yet another embodiment of the current invention, a method and system for controlling forward motion of rotary-wing vehicle  10  of the current invention when power is not applied to auxiliary power system  400  of  FIG. 1 . In accordance with the current invention, an ability is provided to move the power source assembly  604  back and forth by simple mechanical means in order to change flight characteristics. A center of gravity of rotary-wing vehicle  10  of the current invention can be adjusted inline with main rotor drive shaft  300  to enable rotary-wing vehicle  10  to hover steadily when power is not applied to auxiliary power system  400  of  FIG. 1 . 
     Alternatively by moving power source assembly  604  forward, the center of gravity of rotary-wing vehicle  10  may be adjusted ahead of the main rotor drive shaft  300  central line. In such case rotary-wing vehicle  10  will have a slow forward flight when auxiliary power  400  of  FIG. 1  is not operating. 
     By moving power source assembly  604  even further forward, the center of gravity can be adjusted further ahead of the main rotor drive shaft  300  central line, resulting in a faster forward flight when no power is applied to auxiliary power  400 , thus with less energy power consumption. Adjusting a simple knob  610  by displacement mechanisms, such as a screw mechanism  608 , controls the center of gravity backwards/forwards relative to main rotor drive shaft  300  central line. Alternatively, a sliding apparatus may be used for the center of gravity location control. 
     Reference is now made to  FIGS. 8A and 8B , which are illustrations of yet another preferred embodiment of the current invention.  FIG. 8A  is an upper view of blades  202  and  204 . One preferred embodiment of the current invention is main rotor blades  202  and  204  (and similarly main rotor blades  102 ,  104  of  FIG. 1 ) with a lifting force center  920 , which is located ahead of pitch axis  914 .  FIG. 8A  shows one such preferred implementation, where blade set  202 ,  204  is swept forward. 
     It would be appreciated that by implementing forward swept blades of the current invention, the advancing blade lift  924  creates a blade pitching moment around the pitch axis which is opposite of blade pitching moment  922  of  FIG. 8B , therefore, the net pitching moment of the blades around the rotor head pitch axis is zeroed or positive with respect to the direction of flight. Positive moment in that case means a moment that attempt to tilt back the rotor head when the pitch axis is perpendicular to the direction of flight. This pitch moment affects the fly bar  207  plane of rotation in a desired manner and improves flight stability. 
     At any wind speed  928  other than zero (hovering) the pitching moment of the advancing and retarding blades does not cancel each other. If the blades are not swept forward and have their lift center aligned with the pitch axis then the increased pitching moment of the advancing blade sums up with the decreased pitching moment of the retarding blade and will cause such a net pitching moment on the rotor head that will attempt to tilt the fly bar forward into the wind. As a result, acceleration and diverging into a crash may occur. It would be appreciated that with forward swept blades of present invention, net pitch moments  930  that affect the fly bar may be zeroed, or even in the opposite direction, thus it is possible to eliminate that phenomena. The lift vector of such blades, being aft of the pitch axis, will provide a pitching moment in an opposite direction to the blade natural pitching moment and cancel the effect. The correct forward swept angle for smooth and stable flying may be determined according to the specific blade shape and blade set arrangement. 
     A forward swept blade has also an imaginary axis, which acts as a delta hinge, which reduces the blade pitch when it flaps up, thus adding to the overall stability. 
     Reference is now made to  FIG. 9 , which is an illustration of yet another preferred embodiment of the current invention. 
     Upper rotor blade set  100 , and lower rotor blade set  200 , are designed to be different from each other. The two different designs are meant to create different conning angles between the upper and lower rotor blades while flying. 
     It is yet another embodiment of the current invention that a difference in upper  100  and lower  200  rotor blades may be in their geometry and shape design such as different blade profile, or twist, mass of the blades, blade material type, blade outline shape, different blade speed, and/or any combination of the above options. 
     The different conning angles combine with the forward swept blades and rigid rotor heads, provide pendulum free flight characteristics. 
     Reference is now made to  FIGS. 10A and 10B , which show another method for improving flight quality of yet another embodiment of the current rotary-wing vehicle  10 . 
     Air brakes  850  positioned below the center of gravity (CG) of rotary-wing vehicle  10  create a down pitching moment. With proper selection of the brake size and distance from CG, it is possible to achieve an almost level flight at a speed range of rotary-wing vehicle  10  of present invention. 
     It would be appreciated that adding “pitch up resistance brakes”  850  to a rotary-wing vehicle  10  enables a much smoother flight, and minimizes swinging due to pitch-up that may be created by the forward movement of the rotary-wing vehicle  10 . Pitch up resistance brakes  851 ,  852  function as air brakes. Air brakes  850  of the present invention are located below center of gravity (CG) of rotary-wing vehicle  10 . Preferably air brakes  850  may be added at the lowest possible place to achieve maximum pitching down moment as speed increases. Such location may be at skids  800 . As a result, while the main rotors  100 ,  200  pitch up as speed is picking up, the air brakes  850  keep the rest of the rotary-wing vehicle  10  level or at just at a slight pitch-up angle. With proper selection of pitch-resistance brakes size, a smooth and constant forward speed may be achieved at much higher speeds then without them. Air brakes  850  may be connected by a fixed or dynamic connection. 
     Reference is now made to  FIG. 11A , which, shows another method for improving flight quality of yet another embodiment of the present rotary-wing vehicle  10 , a method for yaw damping that can be used with rotary-wing vehicle  10  by the use of a fixed tail fin  870  (fixed rudder). Fixed tail fin  870  also creates a “windmill” effect, which will point the rotary-wing vehicle  10  nose  871  onto the flying direction while reducing the possibility of flying sideways. 
     In yet another embodiment of the present invention, dynamic air brakes  851 ,  852 , can be used for steering left/right of rotary-wing vehicle  10 . Actuators  860 ,  862 , such as solenoids, can change air brakes  851 ,  852  position to increase/decrease the air resistance changing flight direction. It would be appreciated that using this steering method rotary-wing vehicle  10  may use only one auxiliary motor. An auxiliary forward/backwards motor will be centered aligned with the main rotor coaxial shaft as shown in  FIG. 11B . 
     Reference is now made to  FIG. 11B , which shows yet another innovative method for steering left/right the Rotary-wing vehicle  10 . An actuator  882  controls a steering tail  880 . Operator may control the steering tail by controlling the steering actuator  882 . 
     Referring again to  FIG. 1 , body  12  of rotary-wing apparatus  10  may be made of foam, or possibly a low weight material such as thin lightweight plastic, or cardboard. Skids  800  are made from foam, or other lightweight materials and rotor blades  100 ,  200  are made of foam and or cardboard, or other lightweight and flexible materials. 
     Rotary-wing apparatus  10  may be controlled by remote controller  900 , such as RF remote control unit; alternatively infra-red (IR), or sound control, such as ultra sound remote controllers, may control it. It may also be programmed to operate with no remote controls. 
     It is appreciated that rotary-wing vehicle embodiments of the present invention are typically capable of stable flying forward and backwards, and perform clockwise and counterclockwise yaw maneuvers. It is further appreciated that elimination of a need for movement and acceleration sensors reduces the cost of the rotary-wing vehicle and makes it affordable for consumer products such as toys. 
     It is further appreciated that the rotary-wing vehicle counter rotating blades provide inherent aeronautical stability. Its intuitive flying control enables a layman user to fly a low cost rotary-wing vehicle with very minimal training. 
     It is further appreciated that the rotary-wing vehicle is designed for safe use even in doors. The rotary-wing vehicle is made of elastic materials; main rotor blades are flexible and fold back in case of encountering an external force; low power motors are used; motors may halt on detection of external force. 
     It is further appreciated that the rotary-wing vehicle requires minimal, or no adjustments. Should a yaw or hovering tuning be required, a simple manual adjustment is made possible by simple means such as single knob. 
     It is further appreciated that differential “tank-like” steering of the rotary-wing vehicle is very convenient, provides good yaw control, as well as forward/backwards control of the rotary-wing vehicle flight maneuvers. 
     It is further appreciated that using the same power source for rotating counter-rotating blades of the rotary-wing vehicle eliminates possible drifts in blades behavior over time, such as when two different power sources are used for rotating the counter-rotating blades. Consequently yaw stability over time is significantly better. 
     It is further appreciated that elimination of dynamic main blades pitch control such as actuators, such as used with common helicopters, significantly simplifies the rotary-wing vehicle design, reduces its cost, and makes it more robust and reliable. 
     It is further appreciated that elimination of a tail propeller, such as used with common helicopters, simplifies the rotary-wing vehicle design, reduces cost, and increases reliability, stability and maneuverability. 
     It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and sub combinations of the various features described hereinabove as well as variations and modifications which would occur to persons skilled in the art upon reading the specification and which are not in the prior art.