Abstract:
An apparatus that includes a rotor blade assembly capable of generating vertical lift, one or more propulsion units capable of engaging and disengaging from the rotor blade assembly, an encapsulating housing, and where the encapsulating housing is capable of containing the rotor blade assembly.

Description:
RELATED APPLICATIONS 
     This application is related to and claims the benefit of U.S. Provisional Application No. 60/376,292 filed on Apr. 29, 2002 titled AIRCRAFT WITH POWERED ROTOR VTOL CAPABILITY and of U.S. Provisional Application No. 60/381,761 filed on May 20, 2002 titled EXTENDING THE AIRCRAFT WITH POWERED ROTOR VTOL CAPABILITY. 
    
    
     FIELD OF INVENTION 
     This invention relates to the field of aircraft and more specifically, to a fixed-wing aircraft having VTOL capability. 
     BACKGROUND OF THE INVENTION 
     Long ground trips through congested freeways to crowded airports having sold-out parking are a fact of life for passengers making use of the current aviation industry at the present time. Add to this the inefficiencies of handling large numbers of passengers and luggage further acts to increase the cost in time, money and the attendant irritation factors. 
     SUMMARY OF THE INVENTION 
     An apparatus and method is described that offers an aircraft the high speed/low drag advantages of conventional fixed wing aircraft with the Vertical Takeoff and Landing (VTOL) ability of rotational wing (rotor) aircraft. The apparatus and method can allow an aircraft to achieve both a pure vertical and horizontal flight and with the capability to quickly transition between these two flight regimes. 
     The apparatus can be propelled in both rotary-wing and fixed-wing modes using a power source such as, for example, a conventional turbofan engine. A rotor such as a two-bladed rotor assembly can be used to generate the required lift for hover, vertical movement, and low-speed forward flight like a helicopter. Once the aircraft is at a sufficient forward velocity, lift from the rotor blade assembly can be removed with lift being provided by the fixed wings, such as, for example, a main wing and a horizontal tail wing. The rotating rotor blade assembly can then be stopped and locked into a position that has the rotor blades aligned along the length of the fuselage. 
     After the rotor assembly is locked in this longitudinal direction, the rotor blade assembly can be stowed in a housing that encapsulates the rotor blade assembly. The fixed-wings then provide the lift in a conventional fixed-wing flight mode. A reverse sequence of these events could transition the vehicle back to its rotary wing-VTOL mode for descent and landing on small landing areas. 
     Techniques for transitioning between vertical and horizontal flight requires coordination between the decrease of downward rotor thrust that dominates during the vertical flight regime with the increase in turbofan jet backward thrust used in the horizontal flight regime. Such coordination must occur progressively, incrementally, and smoothly and where the addition of an attitude control system, jet deflection vanes, and jet exhaust nozzles can add to the control of the transitioning flight regimes. 
     Additional features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which: 
     FIG. 1A is an illustration of one embodiment of a hybrid VTOL aircraft in a vertical flight mode. 
     FIG. 1B is an illustration of an encapsulating housing in vertical the flight mode. 
     FIG. 2A is an illustration of one embodiment of the hybrid VTOL aircraft with a braked rotor blade assembly. 
     FIG. 2B is an illustration of the encapsulating housing with braked rotor blade assembly. 
     FIG. 3A is an illustration of one embodiment of the hybrid VTOL aircraft with a stowed rotor blade assembly. 
     FIG. 3B is an illustration of one embodiment of the encapsulating housing With stowed rotor blade assembly 
     FIG. 4A is an illustration of one embodiment of an external encapsulating housing with dual circular lids. 
     FIG. 4B is an illustration of one embodiment of a cross-section of the external encapsulating housing with dual circular lids. 
     FIG. 5A is an illustration of a cross section of a fuselage and encapsulating housing with clamshell lids. 
     FIG. 5B is an illustration of a hybrid VTOL aircraft with clamshell lids. 
     FIG. 6 is a flow diagram of a method of use of a hybrid VTOL aircraft. 
     FIG. 7 is an illustration of an external encapsulating housing with three stacked rotor blade assemblies. 
     FIG. 8A is an illustration of one embodiment of a hybrid VTOL aircraft with a high-wing and an encapsulating housing integral to the high-wing and the fuselage. 
     FIG. 8B is an illustration of a top view of the one embodiment of the encapsulating housing integral to the high-wing and fuselage. 
     FIG. 9 is an illustration of one embodiment of an external encapsulating housing with an aerodynamically shaped interior surface. 
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth such as examples of specific materials, components, dimensions, etc. in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that these specific details need not be employed to practice the present invention. In other instances, well-known components or methods have not been described in detail in order to avoid unnecessarily obscuring the present invention. 
     The material structures of the invention can be embodied in a hybrid aircraft having both a helicopter type rotor blade assembly and a fixed wing. The hybrid aircraft can be capable of both vertical and horizontal flight. At a point in the transition between vertical and horizontal flight, with flight loads transferred to the fixed wing, the rotor blade assembly can be stopped and positioned within a housing (stowed) to reduce aerodynamic drag. As a result, the hybrid aircraft can be capable of Vertical Takeoff and Landing (VTOL) while retaining a low drag coefficient during horizontal flight that is more typical of pure fixed wing aircraft. 
     Many problems occurring at over-crowded airports can be reduced by utilizing the medium sized, hybrid VTOL (Vertical Take-Off and Landing) aircraft at smaller and more dispersed airports and considering that every helicopter pad could potentially become a node in a world wide network of air transport. As a result, problems for existing airports with in-the-air congestion and aircraft noise affecting citizens living in the surrounding area would also be improved by this dispersing. 
     For military operations, every open and flat landing area can become a node. A military version of the hybrid VTOL aircraft, such as a single-seat fighter or a transport, can gain the benefits of rapid force projection at long range while providing a reduced cost compared to the other VTOL options. 
     In addition to operating among the outer node airports, these hybrid VTOL aircraft could also operate to general aviation airports. This would enable a rapid expansion of airline service to areas that are not currently served. Hence, the air transportation system could readily transform to a more distributed system. A rapid, more efficient service would be realized by landing closer to the terminal, thereby minimizing aircraft taxi time, noise and emissions. Thus approach could increase national mobility and accessibility, with minimum environmental impact. 
     The hybrid VTOL aircraft can be designed for small to medium sized aircraft, that is, to carry approximately 1-100 passengers. The hybrid VTOL aircraft can use the rotor blade assembly for vertical flight, for hover and loiter, for takeoff and landing, and for low speed horizontal flight. The hybrid VTOL aircraft can have at least one set of fixed wings in the fixed-wing design to provide low-drag lift at the higher horizontal flight speeds when the rotor blade assembly is stowed. 
     FIGS. 1A and 1B are illustrations of one embodiment of a hybrid VTOL aircraft in a vertical takeoff or hover mode. In the one embodiment, the hybrid VTOL aircraft  100  can carry approximately 30-40 passengers. Since the fixed-wing of the hybrid VTOL aircraft provides little or none of the lift at takeoff, the fixed-wing  102  can have a surface area that is reduced from a standard fixed wing aircraft. The reduced fixed wing surface area can provide reduced drag at the higher horizontal flight speeds. A canard wing  103  can be positioned on the fuselage to aid with additional lift and with the flight dynamics. A dual rotor blade assembly  106  can be mounted on top of the fuselage  104 . Positioned between the fuselage  104  and the rotor blade assembly  106 , an external encapsulating housing (housing)  108  can be disposed along the longitudinal axis  110  of the fuselage  104 . The external encapsulating housing  108  can be constructed so as to be strong enough to withstand aerodynamic loads and minimize vibrations during flight. Such strength can be the result of a stiffness of the housing  108 , which can be related to the strength of the materials used and the size and shape of the housing  108 . Twin turbofan engines  112  can be mounted on opposite sides of the fuselage  104  and close to a rotor hub (includes shaft)  114  that connects the individual rotor blades  107 . 
     As shown in FIG. 1B, the encapsulating housing  108  can be a tube of a length capable of housing the rotor blade assembly  106 . The housing  108  can include a base tube  118  having a top-positioned opening  119 , an aerodynamically shaped nose cone  120 , an aerodynamic shaped tail cone  122 , and a circular, such as, for example a semi-cylindrical shaped lid  124 . The lid  124  can be capable of rotation around the base tube  118  to open or seal the top opening  119 . A slot  126  in the lid  124  can provide clearance around the rotor hub  114  when the lid  124  is rotated within the base tube  118  and the encapsulating housing  108  is “open” (as shown). 
     The encapsulating housing  108  can be positioned adjacent to the rotor blade assembly  106  and where translating mechanisms  116  such as actuators and/or hydraulic pistons can attach the housing  108  to the fuselage  104 . The translating mechanisms  116  can be capable of raising and lowing  128  the encapsulating housing  108 , that is moving the encapsulating housing  108  toward the rotor blade assembly  106  or toward the fuselage  104  respectively. 
     As shown in FIG. 1A, for both rotary and fixed-wing flight modes, the hybrid VTOL aircraft can be powered by one or more conventional turbofan engines  112 . The twin turbofan engines  112  can have jet exhaust nozzles  115 , which can be capable of deflecting a portion of the engine  112  exhaust downward to produce a vertical thrust vector that can add to the vertical lift force created by the rotating rotor blade assembly  106 . In one embodiment, torque created by the rotating rotor blade assembly  106  may be countered by thrust from gas escaping a nozzle  115  positioned in the vertical tail section  111 . A portion of the compressed air within the jet engines  112  can be diverted into a system that ports the diverted gas to the anti-torque nozzle  115 . 
     In one embodiment the aircraft can utilize diverter valves that direct the exhaust thrust to the rotor blade tips to exhaust at a jet nozzle and drive the rotor blade assembly  106  to rotation (not shown). Alternatively, in one embodiment, a drive train and transmission can be used as a direct power link to transfer power from the turbofan engines  112  to the rotor blade assembly  106 . 
     In one embodiment, the aircraft can be made of a composite fiber fuselage with aluminum internal structure to form an approximate 30-40 seat pressurized composite cabin. The fuselage  104  can be locally reinforced such that the two composite turbofan engines  112  can be attached to the fuselage  104  close to the rotor hub/shaft  114  to minimize power linkage losses. 
     Using the rotor blade assembly  106 , the hybrid VTOL aircraft  100  can be capable of taking off, landing, and hover like a traditional helicopter. A combination of lift from the rotor blades  106  and the downward vectored jet engine  112  thrust, can provide a mechanism for loiter, i.e. the ability to move around slowly in a small area for long periods of time. With the rotor blade assembly  106  in the stowed position (FIG.  1 B), the hybrid VTOL aircraft  100  can be capable of the high-speed flight and wide radius of operation that is typical of a standard fixed-wing jet airplane. It can take approximately 1 min for the hybrid VTOL aircraft  100  to switch modes between pure helicopter and pure fixed-wing airplane, i.e. to transition from vertical to horizontal flight. 
     FIGS. 2A and 2B are illustrations of one embodiment of the hybrid VTOL aircraft in transition to horizontal flight and after having braked the rotor blades. Once the hybrid VTOL aircraft  200  has obtained sufficient horizontal airspeed, lift provided by the fixed-wings  202  can allow the rotor blade assembly  206  to be stowed within the housing  208  and housing lid  209 . The rotor blade assembly  206  can first be braked, i.e. stopped, so as to place the individual rotor blades  207  in-line with the axis  210  of the fuselage  204 . As a result, the rotor blades  207  can be aligned with the opening  219  in the housing  208  such that later translation by the housing  208  can encapsulate the rotor blade assembly  206 . 
     FIGS. 3A and 3B are illustrations of one embodiment of the hybrid VTOL aircraft in horizontal flight with a stowed rotor blade assembly. The aerodynamically shaped housing  308  is shown moved up  328  by translating mechanisms  316  to place the rotor blade assembly  306  (shown as dashed lines) within the base tube  318 . Two semi-cylindrical shaped housing lids  324  are shown rotated approximately between 150-180 degrees to seal the rotor blade assembly  306  within the encapsulating housing  308 . A gap  312  can exist between the housing lids  324  to provide clearance around the rotor shaft  314 . After the housing lids  324  are rotated  316  to a closed position as shown, a sleeve  318  (shown in dashed lines) can be translated  320  by a device (not shown) such as, for example, a jackscrew, to seal off the gap  312 . With the rotor blade assembly  306  encapsulated within the housing  308 , horizontal flight speeds can then be increased. 
     FIGS. 4A and 4B are illustrations of one embodiment of an encapsulating housing having a clamshell lid. The clamshell design can have two curved lids  430  and  432 , each with a slot  434  and  436 . The curved lids  430  and  432  can be positioned on each side of a top opening  419  of the housing  408 . As shown, the two curved lids  430  and  432  can be capable of rotation  436  to close the top opening  419  and where the slots  434  and  436  in each curved lid  430  and  432  can provide clearance for the rotor shaft  414 . The housing  408  can be capable of up and down  438  translation to place the stopped rotor blades  407  within or outside of the housing  408  when the rotor blade assembly  406  is being stowed (not shown) or un-stowed (as shown). Translation of the housing  408  can be accomplished by such mechanisms as, for example, actuators and/or hydraulic pistons  440 . 
     During transition from vertical to horizontal flight, and as the lift contribution shifts from the rotor to the fixed wings, the aircraft must (1) make a smooth transition between the two modes in a manner that prevents rotor blade excessive vibration, and (2) reduce the rotor speed to stop. The rotor blade stiffness must be designed accordingly to reduce rotor blade flutter and allow for encapsulation of the rotor blade assembly within the encapsulating housing. 
     Because the primary fixed-wing is not needed for low speed flight, the fixed-wing can be significantly smaller than fixed-wings on standard aircraft, which can reduce the required cruise power. The resulting speed, range, altitude capability and fuel economy can compensate to some extent for the drag created by the externally positioned housing  108 . In one embodiment, a 2-bladed rotor can be a continuous tip-to-tip composite structure comprising the blade and hub in a single unit. 
     With increased forward velocity, the main wings will provide increased lift. At a point in the transition between vertical and horizontal flight, the rotor will be sufficiently unloaded that power to the rotor blades can removed. As soon as the power linkage is removed from the rotor blade assembly, a braking mechanism (not shown) can slow rotation of the rotor blade assembly. The braking mechanism can stop the rotor blade assembly such that the individual rotor blades are in-line with the length of the fuselage and ready for encapsulation within the housing. 
     FIGS. 5A and 5B are illustrations of one embodiment of the hybrid VTOL aircraft. As shown in FIGS. 5A &amp; 5B, encapsulating a rotor blade assembly  506  can be accomplished with a clamshell design that can have two rotatable doors  509  and  511  that can have a length L, which can be a partial length of the fuselage  504 . The encapsulation process does not require the rotor blade assembly  506  to translate up and down. Rather, two rotatable doors  509  and  511 , when open, can allow the rotor blade assembly  506  to be rotated to provide vertical lift. When closed, the two rotatable doors  509  and  511  can complete the encapsulation of the rotor blade assembly  506  for pure fixed wing flight. The two rotatable doors  509  and  511  can be curved to follow a shape  516  of the fuselage  504  (i.e. mate with). The rotatable doors  509  and  511  can be capable of pivoting  513  at several locations  514  between an open position (doors shown in dashed lines) to a closed position (solid lines) where the closed position can seal the rotor blade assembly  506  within the encapsulating apparatus, i.e. the fuselage  504  and the doors  509  and  511 . The turbofan engines  512  can be positioned low enough on the fuselage  504  to provide clearance for the pivoting doors  509  and  511  yet close enough to the rotor hub  515  for convenient mechanical linkage (not shown). A forward end of the fuselage  504  can provide an aerodynamic shield  516  to airflow and along with an aft end  517  of the fuselage  504 , can complete the encapsulation of the rotor blade assembly. 
     FIG. 6 is a flow diagram of one embodiment of a method for encapsulating a rotor blade assembly. A hybrid VTOL aircraft can be grounded with the housing lowered, exposing the rotor blade assembly. Turbofan engines can power the rotor blade assembly along with downward thrusting by rotatable jet engine nozzles and vertical lift can be generated. If multiple stacked rotor blade assemblies are used, a phase angle between the blades of each rotating rotor blade assembly can be maintained. An attitude reaction control system using air pressure bled off from the jet engines can add to the control of the hybrid VTOL aircraft at this point (operation  602 ). The reaction control system can have at least one small jet positioned at the nose, tail, and wing tips of the aircraft. Sufficient vertical lift can be generated to place the hybrid VTOL aircraft into vertical flight (operation  604 ). The nozzles can progressively rotate the jet engine thrust backward, and along with the rotor blade assembly, the hybrid VTOL aircraft can transition into horizontal flight (operation  606 ). The nozzles are providing purely backward thrust from the jet engines and the horizontal velocity is sufficient to have lift provided by the fixed-wings. Power can be progressively removed from the rotor blade assembly until the rotor blade assembly is free from powered rotation (operation  608 ). Horizontal speed is increased to allow loading on the fixed wings to maintain the hybrid VTOL aircraft in flight (operation  610 ). The rotor blade assembly is braked to position the individual rotor blades to be inline with the length of the housing (operation  612 ). Actuators translate the housing up to position the rotor blade assembly within the housing (operation  614 ). One or more curved lids can be rotated to complete the encapsulation of the rotor blade assembly within the housing (operation  616 ). The hybrid VTOL aircraft can now operate as a fixed-wing aircraft. The transition to pure fixed-wing horizontal flight is complete. The transition from fixed-wing flight to vertical flight for landing, hover, and/or loiter can be accomplished using a reverse combination of some or all the above-described operations. 
     FIG. 7 is an illustration of one embodiment where multiple rotor blade pairs can be stacked using coaxial rotor shafts. Multiple rotor blade assemblies  702 ,  704 , and  706  can be stacked on top of each other, with the rotor shafts telescoped  708 ,  710 , and  712  to provide more lift within the same approximate space. As shown, multiple pairs of rotor blade assemblies, shown here are three pairs of rotor blade assemblies  702 ,  704 , and  706 , including the respective rotor shafts  708 ,  710 , and  712  stacked within, can be encapsulated in a housing  714 . When the rotor blade assemblies  708 ,  710 , and  712  are braked and aligned along the length of the housing  714 , the housing  714  can be translated in an up and down direction  715  by, for example, actuators and/or hydraulic pistons  716 . During operation of the rotor blade assemblies  702 ,  704 , and  706 , the rotor blade assemblies  702 ,  704 , and  706  can have a phase angle, such as, for example, with three pairs of rotor blades, a 60-degree phase angle for each rotor blade relative to a next rotor blade of another rotor blade assembly  702 ,  704 , and  706 . 
     FIGS. 8A and 8B are illustrations of one embodiment of an encapsulating housing that is integral to the airframe of a high-wing aircraft. A triple-rotor blade assembly  804  can be capable of recessing into the integral housing  802  where the housing  802  involves both the fuselage  806  and the fixed high-wing  808 . The triple-rotor blade assembly  804  can be capable of up and down  810  translation to place the rotor blade assembly  804  within and outside the housing  802  for stowing (shown) and un-stowing (not shown) using a device (not shown) such as the jackscrew. Slightly curved or flat sleeves (shown as dashed)  810  can be positioned within the fuselage and the high-wing that can be capable of translation to cover an opening  812  in the housing  802  to seal the housing interior  814  from air flow before and after stowing and un-stowing of the rotor blade assembly  804 . 
     FIG. 9 shows a cross-section of an encapsulating housing that has interior surfaces shaped to reduce turbulence and promote smooth laminar flow of air. The encapsulating housing  902  can be shaped to reduce turbulence and promote laminar flow from air around and through an open housing  902 . Airflow  916  can exit the interior of the housing  902  through an opening  914  at the aft end of the housing  902 . Shaping, such as a tapered nose surface  904  and tapered end surface  906 , can allow the airflow to bend around the housing  902  interior and exterior surfaces to minimize turbulence. Such shaping can be accomplished on interior surfaces of both an external housing  902  as well as an integral housing  802  (see FIG.  8 A). Turbulent airflow around the rotor blades  908  could create problems by causing the rotor blades  908  to flex or vibrate in a manner that would make stopped rotor blades  908  difficult to stow. Further, the housing  802  can be aerodynamically shaped to minimize turbulence along the inner surfaces as a result of rotor blade downwash. 
     The housing  902  can be shaped to make use of the Coanda effect to bend the airflow along the housing interior  910  contours during horizontal flight. The Coanda effect relates to the tendency of a fluid flow when striking an object, to create a boundary layer along the surface with the result that the flow follows the surface of the object. The housing  902  can be shaped to allow for air flowing along the housing interior surfaces  910  to reduce turbulence which can affect the ability to stow the rotor blades  908 . In addition, the housing  902  can have small vanes  912  placed in the contoured surfaces  910  exposed to the airflow. The vanes  912  can be positioned perpendicular to the curved surface  910 . Angled into the airflow, the vanes  912  can produce small vortices, which may delay boundary layer separation and further reduce turbulence and may also reduce drag. 
     In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.