Abstract:
The pressure jet propulsion disclosed herein generally includes an air compressor for generating a mass flow of compressed air and a mast mount assembly in fluid communication with the air compressor for receiving and channeling the mass flow of compressed air. A positioning system supports the mast mount assembly and is movable on-demand to relocate the mast mount assembly relative to a center of gravity in response to environmental changes. Furthermore, at least two blades are in fluid communication with the mass flow of compressed air from the movable mast mount assembly, which is discharged through an outlet at an angle relative to an axis of rotation to cause rotation of the blades.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention generally relates to a pressure jet propulsion system for a helicopter or the like. More specifically, the present invention relates to a pressure jet propulsion system for a helicopter that includes rotor blades driven by compressed air that travels up a mast, into the rotor head, down the length of each blade and exits at the tip of the blade causing the rotor blades to rotate. 
         [0002]    Conventional helicopter technology started in about the 1940&#39;s. At that time, two main technologies were being developed, one that included a rogue version of the pressure jet propulsion technology as has been improved upon herein, and the more conventional and well known designs that were developed around a piston driven engine and turbine engine with direct drive technology. Pressure jet propulsion technology back in the 1940&#39;s and 1950&#39;s did not reach the appeal of manufacturers due to the limited development of engine and compressor technologies and the undesirable weight of the components at the time. Although, over the years, many different prototype helicopters incorporating pressure jet propulsion technology have been successfully built and flown. Despite this, manufacturers have primarily diverted helicopter development toward more conventional types of engines, transmissions, tail-booms and rear rotors, as are well known and in use today. 
         [0003]    In a conventional helicopter, the driving force that rotates the blades comes from a mechanical link to a transmission driven by an engine. When power is applied to the drive shaft of the main rotor system, counter-torque is developed, which causes the fuselage of the helicopter to rotate in the opposite direction. To counter this yaw movement of the fuselage, a rear rotor vertically mounted on a tail boom is required to direct the fuselage. Any time power is applied to the drive shaft of the main rotor system, such as in lift-offs, turns, ascending or descending maneuvers, corrective yaw control is always required via foot pedals that change the pitch of the rear rotor blades. This change in pitch requires power changes which again cause counter-torque. Thus, a pilot must always attend to this never ending corrective action when flying a helicopter. 
         [0004]    Conventional helicopters also have a complex mechanical assembly of components that interconnect the main rotor with the tail rotor. More specifically, there is a main transmission for the main rotor, a reduction gearbox for the rear rotor, a clutching system to disengage the main rotor in the event of engine failure, couplings, drive shafts, and in some cases belts that connect all of these components together. These components are not only relatively heavy, but they require frequent and costly maintenance. 
         [0005]    There exists, therefore, a significant need for a pressure jet propulsion system that includes fewer components than conventional helicopter technology, which corresponds to light weight and greater payload capacity, reduced manufacturing costs, including design, production and assembly; and, as a result, considerably less annual maintenance, and elimination of counter-torque, thereby making the helicopter easier to fly. The present invention fulfills these needs and provides further related advantages. 
       SUMMARY OF THE INVENTION 
       [0006]    In accordance with the disclosures made herein, one embodiment for a pressure jet propulsion system includes an air compressor for generating a mass flow of compressed air and a mast mount assembly in fluid communication with the air compressor for receiving and channeling the mass flow of compressed air. A positioning system supports the mast mount assembly and is movable on-demand to relocate the mast mount assembly relative to a center of gravity, which may be specific to a helicopter, for example, and based on the number and weight of the passenger(s), luggage weight distribution, and other payload distribution(s), such as fuel. At least two blades are in fluid communication with the mass flow of compressed air from the movable mast mount assembly and include respective outlets along the length thereof for discharging the mass flow of compressed air at an angle relative to an axis of rotation, thereby causing the blades to rotate. In a particularly preferred embodiment, the pressure jet propulsion system is for use with a helicopter that includes an engine-driven air compressor that delivers a high mass flow of compressed air through ducts formed in the mast mount assembly and blades. 
         [0007]    The positioning system may include a rail system having a pair of inwardly extending linear rails that reciprocally engage a pair of linear bearings in a base of the mast mount assembly. Here, the linear bearings ride on the linear rails and preferably allow the positioning system to move in both longitudinal and lateral directions, and preferably at least accommodates fore-aft movement. A load sensor may monitor the center of gravity and provide feedback to a controller that adjusts the positioning system on-demand. In this respect, a mast servo drive operated by the controller may accordingly locate and relocate the mast mount assembly on the track system. The mast mount assembly preferably includes a partially flexible duct to permit such movement relative to the otherwise stationary compressor and frame. 
         [0008]    In one embodiment, the air compressor may include an engine-driven air compressor that can generate a mass flow of compressed air in the range of 3,000 to 5,000 cubic feet per minute (cfm) and typically in a temperature range between 300 and 500 degrees Fahrenheit. At temperatures in this range, conventional de-icing procedures or the type normally used with helicopters during cold weather conditions can be simplified or eliminated altogether. It may be desirable to include a heat sink coupled in line with the mast mount assembly to dissipate heat generation therefrom. Here, a pair of airfoil links may at least partially rotatably surround the heat sink and have a geometry configured to direct air over the heat sink when the blades are rotating. A heat sink that includes a plurality of fins may increase the surface area dissipation of heat and increase cooling efficiency. When used in association with a helicopter, the pressure jet propulsion system may further include a tail rudder for deflecting exhaust gasses emitted by the air compressor to further control movement. 
         [0009]    In another embodiment, the pressure jet propulsion system may include an air compressor for generating a mass flow of compressed air and a mast mount assembly in fluid communication with the air compressor for receiving and channeling the mass flow of compressed air. In this embodiment, a rotor hub fluidly couples with the mass flow of compressed air from the mast mount assembly and fluidly couples to at least two blades extending therefrom. The rotor hub is pivotable on-demand to upwardly or downwardly reposition the at least two blades. In this respect, movement of the rotor hub may advance the at least two blades upwardly or recede the at least two blades downwardly. An outlet along each of the at least two blades discharges the mass flow of compressed air at an angle relative to an axis of blade rotation to cause the blades to rotate. 
         [0010]    More specifically, the rotor hub includes a hollow rotor head and a spindle, the spindle being fluidly coupled to a top portion of the mast mount assembly. The rotor head also includes an arcuate surface pivotable relative to a reciprocally concave surface of the spindle. An O-ring may sit in a groove in the concave surface of the spindle, thereby permitting the rotor head to pivot hermetically relative to the spindle. Furthermore, the rotor hub may include a coupler for rotatable mounting to an airfoil link and a pin for pivotal coupling to a mounting fixture. Moreover, this embodiment may include at least two blade grip spindles respectively coupling the rotor hub to the at least two blades. Additionally, at least two blade grip bearing housings may respectively rotatably mount relative to the at least two blade grip spindles, the at least two blade grip bearing housings including a heat sink cooled by airflow during blade rotation. The at least two blade grip spindles include a circular flared end coupled to the rotor hub and a flat generally rectangular end for respective nested reception with the at least two blades. A collective may couple to the rotor hub, for increasing and decreasing elevation of the blades. 
         [0011]    In another embodiment disclosed herein, the pressure jet propulsion system may include an air compressor for generating a mass flow of compressed air and a mast mount assembly in fluid communication with the air compressor for receiving and channeling the mass flow of compressed air. In this embodiment, a swashplate assembly is mounted concentrically over a spherical ball section of a sleeve slidably mounted relative to the mast mount assembly. The swashplate assembly preferably includes an upright post pivotally coupled to a rotor head having at least two blades extending therefrom and in fluid communication with the mass flow of compressed air from the mast mount assembly. The upright post preferably includes a pair of upright posts pivotally coupled to a pivot arm extending from a blade grip bearing housing. As described above, an outlet along each of the at least two blades discharges the mass flow of compressed air at an angle relative to an axis of rotation, wherein angled discharging causes the at least two blades to rotate about the axis of rotation. Furthermore, a pair of airfoil links may couple with the swashplate assembly and the rotor head such that the airfoil links rotate with the rotor head about a heat sink. Preferably, the airfoil links include a geometry configured to direct air over the heat sink, which may include a series of cooling fins extending away from the mast mount assembly. 
         [0012]    More specifically, the swashplate assembly may move globally about a center of the spherical ball section and modify the global horizontal position of the at least two blades relative to a zero plane to change the pitch of the at least two blades in a forward, rearward, leftward or rightward manner by way of global movement about the spherical ball section. Although, a linkage assembly may limit radial movement of the swashplate assembly relative to the sleeve, while providing limited sliding movement of the sleeve relative to the mast mount assembly. Additionally, the swashplate assembly further includes a three piece inner ring assembly that includes an upper inner ring and a two piece lower inner ring and a two piece outer ring assembly that includes an upper outer ring and a lower outer ring. The three piece inner ring assembly and the two piece outer ring assembly couple about a radial bearing such that the inner ring assembly is stationary and the outer ring assembly is free to rotate about the radial bearing. 
         [0013]    In another embodiment disclosed herein, the pressure jet propulsion system may include an air compressor for generating a mass flow of compressed air and a mast mount assembly in fluid communication with the air compressor for receiving and channeling the mass flow of compressed air. In this embodiment, the pressure jet propulsion system includes at least two blades each having a hollow interior with a duct therein in fluid communication with the mass flow of compressed air from the mast mount assembly. Each of the ducts includes a pair of indexing flanges offsetting the duct from the hollow interior of each blade to form a thermal gap therebetween. The duct may include multiple inter-fitting duct sections assembled together by slip fit engagement. An outlet along each of the at least two blades discharges the mass flow of compressed air at an angle relative to an axis of rotation, wherein angled discharging causes the at least two blades to rotate about the axis of rotation. Preferably, the ducts include an outlet tip that includes a sweep duct tip or a dead head transition tip. The sweep duct tip preferably includes an L-shaped curve to discharge the mass flow of compressed air at a 90 degree angle relative to a longitudinal length of the blade. 
         [0014]    Preferably, the longitudinal surfaces of the duct expand and contract about the indexing flanges and within the thermal gap in response to thermal changes. The pair of indexing flanges may include a fore and aft flange or a top and bottom rib. A pair of blade grip transition ducts may respectively couple the mass flow of compressed air from the mast mount assembly to each of the at least two blades. Rotational speed of each of the at least two blades is a function of the speed of mass flow of compressed air discharging from each of the outlets. In this respect, increasing the mass flow of compressed air out through each outlet increases rotational speed of the at least two blades, and decreasing the mass flow of compressed air out through each outlet decreases the rotational speed of the at least two blades. In a particularly preferred embodiment, the each of the least two blades are made from aluminum, titanium, or a composite material and the duct is made from stainless steel. Of course, the specific number of blades may vary. 
         [0015]    Other features and advantages of the present invention will become apparent from the following more detailed description, when taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The accompanying drawings illustrate the invention. In such drawings: 
           [0017]      FIG. 1  is a perspective view showing the front and right sides of a helicopter incorporating one embodiment of a pressure jet propulsion system as disclosed herein; 
           [0018]      FIG. 2  is an enlarged perspective view of the pressure jet propulsion system, including a centrifugal compressor, a hollow mast assembly including a swashplate, and at least two hollow rotor blades; 
           [0019]      FIG. 3  is a alternative perspective view of the helicopter of  FIG. 1 ; 
           [0020]      FIG. 4  is a rear and right side perspective view of the helicopter of  FIGS. 1 and 3 , further illustrating an exhaust system for the yaw control of the helicopter; 
           [0021]      FIG. 5  is a partial cut-away schematic view of the helicopter of FIGS.  1  and  3 - 4 , illustrating fore-aft movement of the mast assembly for trimming; 
           [0022]      FIG. 6  is an enlarged perspective view of the mast coupled to the helicopter, and further illustrating both longitudinal and latitudinal mast movement; 
           [0023]      FIG. 7  is an enlarged perspective view of a blade grip and rotor blade assembly; 
           [0024]      FIG. 8  is an enlarged perspective view of a head for mounting onto an upper end of a mast assembly; 
           [0025]      FIG. 9  is an enlarged perspective view of the mast assembly; 
           [0026]      FIG. 10  is an enlarged perspective view of a trimmable mast mount assembly for mounting onto a lower end of the mast assembly; 
           [0027]      FIG. 11  is an enlarged perspective view of an engine-driven centrifugal compressor; 
           [0028]      FIG. 12  is an enlarged exploded perspective view illustrating assembly of the entire pressure jet propulsion system components for a helicopter, as disclosed herein; 
           [0029]      FIG. 13  is another enlarged and partially exploded perspective view illustrating a mast post and a related bearing housing; 
           [0030]      FIG. 14  is an enlarged and partially exploded perspective view illustrating the mast post for coupling with the trimmable mast mount assembly; 
           [0031]      FIG. 15  is an enlarged and partially exploded perspective view of a blade grip spindle for coupling with a rotor head assembly; 
           [0032]      FIG. 16  is an enlarged and partially exploded perspective view of a blade grip unit for coupling with a blade grip bearing housing; 
           [0033]      FIG. 17  is an enlarged and partially exploded perspective view of the rotor blade for the helicopter for coupling with the blade grip unit; 
           [0034]      FIG. 18  is an enlarged perspective view of an exemplary rotor blade ducting for the helicopter; 
           [0035]      FIG. 19  is an enlarged perspective view of ablade grip transition duct including a flange and lower and upper ducting sections welded together; 
           [0036]      FIG. 20  is an enlarged and partially exploded perspective view illustrating a blade tip duct having a rearwardly sweeping or curving duct shape terminating in a relatively narrow outlet duct port, in accordance with one preferred embodiment; 
           [0037]      FIG. 21  is an enlarged and partially exploded perspective view showing a two-piece blade tip duct having a capped end with a rearwardly facing outlet duct port, in accordance with an alternative embodiment; 
           [0038]      FIG. 22  is an enlarged perspective view illustrating a slip-fit arrangement between duct sections and the blade tip duct ends of  FIG. 20  or  21  onto the radially outermost end of the blade duct, to accommodate expansion and contraction therebetween; 
           [0039]      FIG. 23  is an enlarged perspective about the circle  23  in  FIG. 22 , further illustrating the slip-fit arrangement; 
           [0040]      FIG. 24  is an enlarged perspective view showing the cross-sectional internal rotor blade construction in accordance with one preferred embodiment; 
           [0041]      FIG. 25  is another enlarged perspective view showing the internal rotor blade construction in accordance with an alternative preferred embodiment; 
           [0042]      FIG. 26  is an enlarged perspective view showing details of an externally finned blade grip bearing housing; 
           [0043]      FIG. 27  is an enlarged perspective view showing details of the externally finned mast bearing housing; 
           [0044]      FIG. 28  is an enlarged and partially exploded perspective view illustrating airfoil links attached to the mast bearing housing and for attachment to a swashplate unit; 
           [0045]      FIG. 29  is an enlarged and partially exploded perspective view showing a dual blade head with blade flapping motion; 
           [0046]      FIG. 30  is an enlarged and partially exploded perspective view showing the dual blade head of  FIG. 29  in combination with a sealed attachment to an underlying mast or spindle; 
           [0047]      FIG. 31  is an enlarged and partially exploded perspective view of a 5-blade rotor assembly for mounting at the upper end of the mast or spindle; 
           [0048]      FIG. 32  is an enlarged and partially exploded cut-out perspective view of the 5-blade rotor assembly of  FIG. 31 , and showing the internal passages through the individual rotor blades; 
           [0049]      FIG. 33  is an enlarged perspective view of the swashplate assembly shown generally in  FIG. 9 ; 
           [0050]      FIG. 34  is an exploded perspective view of the swashplate assembly of  FIG. 33 , further illustrating orientation of a pair of inner and outer ring assemblies relative to a radial bearing and a spherical ball section; and 
           [0051]      FIG. 35  is a partial cut-away schematic view illustrating one type of conventional piston driven helicopter capable of being retrofit with the pressure jet propulsion system disclosed herein. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0052]    As shown in the drawings for purposes of illustration, the present invention for a pressure jet propulsion system is generally shown with respect to the embodiments in  FIGS. 1-32 . More specifically, the pressure jet propulsion system disclosed herein is shown generally as integrated into a helicopter  10  as shown in FIGS.  1  and  3 - 6 . Although, persons of ordinary skill in the art will readily recognize that the pressure jet propulsion system may be incorporated into existing helicopter designs as a retrofit system and/or optional propulsion system, such as the helicopter  10 ′ shown in  FIG. 35 . The helicopter  10  can be as simple as the design shown in FIGS.  1  and  3 - 6 , including a tubular frame  12  and skids  14 , a molded fuselage  16 , a cast Titanium rotor hub  18 , at least a pair of fabricated blades  20 , a simple wiring loop with readily available instruments, a Plexiglas windshield  22  and doors  24 , a reciprocating piston engine or turbine engine, a centrifugal compressor  26  and related hardware. More specifically, the pressure jet propulsion system uses an air compressor  26  (FIGS.  2  and  11 - 12 ) to generate compressed air for flow through open ducts or duct passages leading from the compressor  26 , through a mast mount assembly  28 , up into a mast assembly  30 , through a head assembly  32  and out through a plurality of ducted rotor blades  20  leading to exhaustion of the compressed air in a rearward direction from the tip end of each rotor blade  20 . The mass flow rate of compressed air generated by the compressor  26  largely determines the rotational speed of the rotor hub  18  and speed that the rotor blades  20  rotate. 
         [0053]    One main advantage of pressure jet propulsion technology over known conventional direct-drive helicopter propulsion technology that uses piston and or turbine-based engines is that pressure jet propulsion systems eliminate roughly two-thirds of the drive components (and accompanying weight) required to fly the helicopter  10 . Such simplicity decreases the need for sophisticated and expensive components. In this respect, pressure jet propulsion systems do not require main transmissions, reduction gearboxes, clutching systems, couplers, shafts, booms or rear tail rotors. Eliminating these power-robbing and trouble-prone mechanical components, pressure jet propulsion systems of the type disclosed herein are able to achieve considerable savings on weight, thereby permitting a greater payload. Additionally, sophisticated maintenance and training facilities are minimized and safety is dramatically increased. 
         [0054]    The helicopter  10  shown in FIGS.  1  and  3 - 6  is operated by a pressure jet propulsion system  34 , the parts of which are generally shown in relative exploded perspective view in  FIGS. 7-11 , and more specifically described below with respect to FIGS.  2  and  12 - 32 . The helicopter illustrated in FIGS.  1  and  2 - 6  includes the fuselage  16 , the frame  12 , a housing  36 , and a mounted engine (not shown) for powering the centrifugal compressor  26 . The engine operates the compressor  26  to create a volume of compressed air for delivery to the rotor blades  20 , as briefly mentioned above. In this respect, compressed air generated by the compressor  26  is directed into the mast mount assembly  28  through a duct  40  of the centrifugal compressor  26  to a transition duct  42  of the mast mount assembly  28 . This compressed air then travels through the mast assembly  30 , the head assembly  32  and a blade assembly  44  for eventual discharge from the blades  20 , as described in more detail below. 
         [0055]    More specifically with respect to  FIGS. 7-11 , the mast mount assembly  28  receives compressed airflow generated by the compressor  26  through coupling of the transition duct  42  to the duct  40  of compressor  26 . The compressor  26  is solidly mounted to the mast mount assembly  28  and moves in unison with the mast assembly  30 . 
         [0056]    The L-shaped transition duct  42  channels the compressed airflow entering the mast mount assembly  28  upwardly into an upper end  46  thereof for delivery to the mast assembly  30 . The mast assembly  30  includes an inner central duct  48  that includes a flanged lower end  50  that couples to the L-shaped transition duct  42 . The central duct  48  is positioned concentric within a hollow mast post  52  configured for slip fit engagement with the upper end  46  of the mast mount assembly  28 . As more specifically shown in  FIG. 14 , the mast post  52  includes a pair of longitudinal slots  54  perpendicularly traversing a portion of the generally cylindrical outer housing of the mast post  52 . When in slide-fit reception with the upper end  46 , the slots  54  substantially align with a pair of bolt clamps  56 ,  56 ′ that receive respective bolts  58 ,  58 ′. The radial orientation of the mast post  52  is held by locating a vertical slot  59  in the lower end of the mast post  52  with a threaded receptacle  61  in the mast mount assembly  28  and inserting a threaded fastener  63 . The vertical constraint of the mast post  52  is made by the bolts  58 ,  58 ′ engaging the longitudinal slots  54  in the lower end of the mast post  52 . When the bolts  58 ,  58 ′ are inserted and tightened, the bolt clamps  56 ,  56 ′ provide a compression keyed fit to secure the mast post  52  to the mast mount assembly  28 . 
         [0057]    At an upper end thereof, the mast post  52  includes a radially extended surface  60  that includes a plurality of threaded holes  62  configured for threaded reception of respective fasteners  64  designed to attach a non-rotating bearing housing  66  ( FIGS. 9 ,  1   2 - 1   3  and  27 - 28 ) to the mast post  52 . As shown in  FIG. 13 , twelve fasteners  64  attach the bearing housing  66  to the mast post  52  and are designed to carry the full load of the helicopter  10  during operation. The fasteners  64  are safety wired from one another as a means for positively locking the fasteners  64  into the bearing housing  66  and to further prevent the fasteners  64  from loosening due to vibration and other forces during operation of the helicopter  10 . Furthermore, the bearing housing  66  includes an array of external fins  68  defining an extended surface heat transfer area. The external fins  68  function as a heat sink to providing automatic cooling of the heated compressed airflow passing through the central duct  48  of the mast assembly  30 . 
         [0058]    Moreover, the mast assembly  30  further includes a swashplate assembly  70 , shown in FIGS.  9  and  33 - 34 , designed to mount concentrically over an upper spherical ball section  71  (best shown in  FIGS. 12 and 34 ) of a sleeve  72 . When assembled, the swashplate assembly  70  is free to globally move about the center of the upper spherical ball section  71  of the sleeve  72 . The sleeve  72  slides relative to mast post  52  and includes a single lower linkage assembly  74  that includes an upper link  200  and a lower link  202 . The two links  200 ,  202  of the lower linkage assembly  74  limit the radial movement of the swashplate assembly  70  relative to the sleeve  72 , while simultaneously allowing full global movement of the swashplate assembly  70  about the spherical ball section  71 . The swashplate assembly  70  includes a three piece inner ring assembly  76  that includes an upper inner ring  204  and a two piece lower inner ring  206 ,  206 ′ and a two piece outer ring assembly  78  that includes an upper outer ring  208  and a lower outer ring  210 , the ring assemblies  76 ,  78  couple by a radial bearing  212 . The inner ring assembly  76  is held radially from rotating by the linkage  74 , as shown in  FIG. 9  and more specifically in  FIGS. 33-34 . The outer ring assembly  78  is free to rotate with the rotor hub  18  ( FIG. 8 ) as coupled by a pair of upper linkages  80 ,  80 ′ and a pair of airfoil links  84 ,  84 ′. The upper linkages  80 ,  80 ′ globally attach to the outer ring assembly  78  of the swashplate assembly  70  and pivotally attach to a lower end of a pair of airfoil links  84 ,  84 ′ ( FIGS. 9 ,  12  and  28 ) that attach to the head assembly  32  as generally shown in  FIG. 28 . The airfoil links  84 ,  84 ′ rotate with the rotor blades  20  and function in operation to move or displace cooling air over the fins  68  of the bearing housing  66  as a result of the shape of the airfoil links  84 ,  84 ′. The airfoil links  84 ,  84 ′ provide much needed cooling when the helicopter  10  is stationary. Importantly, additional cooling air is moved over the fins  68  as the blades  20  rotate faster, and upon movement of the helicopter  10  when flying. 
         [0059]    The principle purpose of the swashplate assembly  70  is to control the pitch of the blades  20 . The swashplate assembly  70  may be controlled by a “cyclic” (or joystick) that allows the pilot to move the inner ring assembly  76  of the swashplate assembly  70  in a global manner about its center via a linkage (not shown). The outer ring assembly  78  of the swashplate assembly  70  is directly coupled to the rotor hub  18 , and more specifically the blade grip bearing housing  116  by the upright posts  82  and the pivot arm  106  ( FIGS. 8 and 9 ). Movement of the “cyclic” (or joystick) changes the angular position of the swashplate assembly  70  in a global and modified horizontal manner. When the swashplate assembly  70  is in an absolute horizontal plane, the pitch of the blades  20  does not change as the rotor hub  18  coupled to the swashplate assembly  70  rotates. Once the swashplate assembly  70  is pitched in any global position from the horizontal plane, the blades  20  continually change pitch as the rotor head  18  rotates. This change in the blade  20  pitch controls the forward, rearward, leftward and rightward movement of the helicopter  10 . Likewise, ascending and descending movements of the helicopter  10  are controlled by a “collective” lever connected to the sleeve  72  ( FIG. 9 .) by a linkage (not shown). Moving the “collective” (not shown) upwardly or downwardly collectively increases or decreases, respectively, the pitch of the blades  20 , causing elevation changes with the helicopter  10 . 
         [0060]    The head assembly  32  generally includes a rotatable cylindrical spindle  86  held radially by a series of bearings  214  and vertically by threaded fasteners  216  within the bearing housing  66  ( FIG. 12 ). Furthermore, the spindle  86  is configured for slide-fit engagement with the central duct  48  to provide a conduit for compressed airflow traveling from the mast assembly  30  to the head assembly  32  for eventual travel out through the blade assembly  44 , in accordance with the embodiments described herein and best illustrated in  FIGS. 7-9 . Importantly, the spindle  86  includes an upper concave arcuate spindle head  90  ( FIG. 29 ) that includes a pair of airfoil couplers  92  generally extending outwardly from the cylindrical spindle  86 . The airfoil couplers  92  permit attachment of the upper ends of the airfoil links  84  in the manner generally shown in  FIG. 28 . Furthermore, a hollow head unit  94  having a reciprocally arcuate surface  96  ( FIG. 30 ) matching the geometry of the concave arcuate spindle head  90  seals thereto by use of an O-ring seal  98 . The close fit tolerance between the hollow head unit  94  and the spindle  86  with the O-ring seal  98  ( FIG. 30 ) permits air-tight transmission of heated airflow from the ducting in the spindle  86  to the head assembly  32 . The O-ring seal  98  is preferably inserted into a machined groove prior to assembly, which further permits rocking or flapping motion of the hollow head unit  94  relative to the spindle  86  in an airtight manner. 
         [0061]      FIG. 29  illustrates the principle behind the blade flapping head motion between the curved or convex surface  96  and the reciprocally formed curved or concave spindle head  90  with the O-ring seal  98  installed there between to provide a seal for compressed air. The two-blade head unit  94  rotates radially as indicated by the directional arrows shown in  FIG. 29 . The close clearance fit to the spindle  92  provides enhanced precision movement therein. More specifically in this respect, the head unit  94  flaps in an upwardly and downwardly manner, or rocking motion, about an axis  100  ( FIGS. 29-30 ) formed by physically mounting the head unit  94  between a pair of mounting fixtures  102  and a pin  103  ( FIG. 1   2 ). This flapping motion allows the advancing blade(s)  20  to move upwardly and the retreating blade(s)  20  to move downwardly in a natural unrestricted manner during flight. If flapping was not allowed to take place, the helicopter  10  would roll out of control as air speed increases. 
         [0062]    As shown in  FIG. 15 , the head unit  94  couples to a blade grip spindle  108  by eight radial fasteners  110  that carry the full centrifugal load of the rotating blades  20 . These fasteners  110  are also preferably safety wired to one another to prevent loosening during helicopter operation. Compressed air in a hollow passage  112  ( FIGS. 15 and 30 ) of the head unit  94  is diverted to at least a pair of blade grip ducts  114  (one shown in  FIG. 15  for purposes of illustration) for travel to the blades  20 . The head unit  94  accommodates a number of the rotor blades  20 , with  FIGS. 29-30  showing a 2-blade head and  FIGS. 31-32  showing an alternate 5-blade head. Each outlet port or hollow passage  112  of the head unit  94  is coupled to a respective blade grip spindle  108  ( FIG. 15 ) in accordance with the embodiments disclosed herein. 
         [0063]    Additionally, each of the blade grip spindles  108  includes a rotatably mounted blade grip bearing housing  116  having a plurality of external fins  118  similar in construction to those fins  68  used in connection with the bearing housing  66 . The blade grip bearing housing  116  rotates about the blade grip spindles  108  by a bearing structure (not shown) and provides enhanced heat-sink based cooling of the underlying blade grip duct  114  to provide additional cooling of the heated airflow. Adequate cooling of the heated airflow is important so the blades  20  may be made from a lightweight material such as aluminum without the risking damage thereto as a result of the passage of continually highly heated airflow. The blade grip bearing housing  116  is in turn connected at its radially outermost end  120  to a blade grip unit or assembly  122 . As shown best in FIGS.  7  and  16 - 17 , each blade grip unit  122  includes a circular flared end  124  that fits and bolts with one of the blade grip bearing housings  116  at the radially outer end  120  thereof.  FIG. 16  illustrates an exploded perspective view of the blade grip bearing housing  116  relative to the blade grip unit  122  as would be assembled together with the use of the generally radially extending fasteners  126 . These fasteners  126  also carry the full centrifugal load of the rotating blades  20  and are safety wired from one to another to enhance the safety of the helicopter  10 . 
         [0064]      FIG. 17  further illustrates the blade grip unit  122  as having a generally flat rectangular section having a size and shape configured for fitting in nested relation with the rotor blade  20 . Here, the blade grip unit  122  includes a set of three tapered pins or bolts/screws  128  used to fasten the blade  20  to the blade grip  122 . These tapered pins  128  insert through a portion of the blade grip  122  as shown to engage a set of corresponding vertical slots  130  formed in the outer periphery of the blade  20 . When tightened, the pins  128  force the blade  20  forward by wedging the blade  20  within the blade grip  122  and locking the three slots  130  of the blade  20  in place. 
         [0065]    As briefly mentioned above, and in addition to the bearing housings  66 ,  116  that function in part as a heat sink, the blade assembly  44  includes a ducting system designed to provide further insulation against overheating of the outer blade material and a means for providing efficient heated airflow channeling through the blades  20 . In this respect,  FIG. 18  is an exemplary embodiment showing such ducting, including a blade grip transition duct  132 , a blade duct  134  and a blade tip duct  136 . Of particular note, and in general, the ducting system, and in particular the ducts  132 ,  134 ,  136 , of the pressure jet propulsion system  34  disclosed herein make use of a stainless steel construction to manage heat properties and to ensure rigid and non-melting point movement or flexing of the metal material therein. 
         [0066]    More specifically,  FIG. 19  illustrates the blade grip transition duct  132  in more detail. Here, the duct  132  is formed from a three piece welded construction that generally includes a flange  138  formed at one end of inter-fitting lower and upper ducting sections  140 ,  142 , respectively. The flange  138  is generally located at the flared end  124  ( FIG. 17 ) and provides a sheltered or insulated conduit between the blade grip unit  122  and the blade grip bearing housing  116 . The flange  138  is welded to the lower and upper ducting sections  140 ,  142 , which are likewise welded together as shown in  FIG. 19 . To this extent, the blade grip transition duct  132  provides an airtight air flow conduit that couples to the blade duct  134 . 
         [0067]    In this respect,  FIGS. 19-21  illustrate the blade duct  134  as it couples to both the blade grip transition duct  138  at a proximal side ( FIG. 19 ) and the blade tip duct  136  at the distal or radially outer transition tips of the blades  20  ( FIGS. 20-21 ). More specifically,  FIG. 20  illustrates a smoothly curved or sweep outer transition tip  144  having a narrow or slitted rearwardly directed outlet duct port  146  formed therein. In this embodiment, the blade tip duct  136  is generally shaped into an L-shaped curvature to eject heated airflow through the outlet duct port  146  at a generally 90 degree angle relative to the longitudinal length of the blade  20 .  FIG. 21  illustrates an alternative embodiment wherein the blade tip duct  136  is in the form of a so-called dead head transition tip  148  similarly having the narrow or slitted rearwardly opening outlet duct port  146  formed therein, but at a harsher 90 degree angle without a curvature. In this embodiment, the blade tip duct  136  simply includes a cap  150  at its distal end so that heated airflow is directed out through the outlet duct port  146 . 
         [0068]    Compressed air is expelled rearwardly at the radially outer tip end of each rotor blade  20  through the slitted outlet duct port  146 . The expulsion of compressed air through the narrow outlet duct ports  146  formed in the blade tip duct  136  results in the rotation of the rotor blades  20  without the inherent counter-rotation problems encountered in conventional direct-drive helicopter propulsion systems. The faster the relatively high mass flow of air is pumped and expelled through the outlet duct ports  146 , the faster the blades  20  (rotors) will rotate. A typical air compressor, such as compressor  26 , includes a centrifugal compressor having a mass flow capacity on the order of 3,000-5,000 cubic feet per minute (cfm). Additionally, icing precautions during flight are effectively eliminated because compressed air temperatures running through the rotor blades  20  are within the range of about 300-550 degrees Fahrenheit offering natural blade deicing. 
         [0069]      FIG. 22  shows initial slip-fit mounting exemplary in inter-fitting the various ducting components, such as the ducts  132 ,  134 ,  136 , whereas  FIG. 23  is an enlarged perspective view taken about the box  23  of  FIG. 22 , further illustrating such slip fit engagement. As shown in  FIGS. 22-23 , the exit end of a duct section  152  inserts into a flanged inlet end of a duct section  154  having the inlet end of duct section  154  generally bending away from engagement therewith to facilitate slip fit alignment while engaged thereto. 
         [0070]    Furthermore,  FIGS. 24-25  illustrate preferred constructions for lining the interior of the blades  20  with, for example, the aforementioned blade duct  134 .  FIG. 24  illustrates an enlarged perspective view of the blade duct  134  including a fore indexing flange  156 , a top rib  158  and a bottom rib  160 . Moreover,  FIGS. 25  illustrates the blade duct  134  disposed within the interior of the blade  20  and including the fore indexing flange  156 , a pair of top ribs  158 ,  158 ′, a pair of bottom ribs  160 ,  160 ′ and an aft indexing flange  162 . The flanges  156 ,  162  and the series of ribs  158 ,  158 ′,  160 ,  160 ′ bias the blade duct  134  away from direct engagement with the interior of the blade housing  20 . This feature controls ballooning of the rotor blade  20  in response to heated compressed airflow therethrough and provides an air cooled buffer between the substantially heated ducting and the blades  20 , which may also include a ceramic coated inside surface to provided additional heat shielding. 
         [0071]    Accordingly, inclusion of the aforementioned ducting  132 ,  134 ,  136  within the interior of the blades  20  and fabricating the blades  20  from metal less prone to material changes as a result of expansion/contraction from heating and cooling, the pressure jet propulsion system  34  tends to have blade assemblies  44  that are heavier than the composite blade assemblies of conventional direct-drive helicopters. In this respect, the rotor system tends to be inherently more stable because of the increased weight of the blade assemblies  44 . The heavier rotor blades  20  also provide a higher degree of gyroscopic stability to the helicopter  10 , which means less pilot concern over wind gusts and rotor disturbances. 
         [0072]    Additionally, helicopters have a specially designated center of gravity or lift point. While a helicopter, such as the helicopter  10  disclosed herein, has a specifically designated center of gravity, it is not always necessary to be in exact balance to fly. Instead, for example, the helicopter  10  can operate within a window of acceptable loading and still be considered within its center of gravity or simply in balance despite not being exactly in balance. But, helicopter controls and range of motion are designed around a specific point of balance. To this end, the center of gravity and balance of a helicopter is determined by the placement of passengers  164  (e.g., as shown in FIGS.  1  and  3 - 6 ), the weight and location of baggage and the amount of fuel remaining at any given time. As the number of passengers, baggage and/or fuel changes, so does the center of gravity and balance of the helicopter. 
         [0073]    When a conventional helicopter is loaded out of balance, the pilot normally compensates by changing the position of the cyclic or “joy stick”. For example, in a heavy nose condition, the cyclic or joy stick is pulled back to maintain level flight. As the helicopter burns fuel, the cyclic or joy stick must be pulled back even further. The obvious disadvantage here is that the pilot may run out of backward travel of the cyclic to maintain level flight, which can prevent the pilot from maintaining the nose in a safe landing position. Furthermore, the pilot must constantly pull back on the cyclic during flight. This condition requires that the pilot constantly maintain active engagement with the cyclic or else the helicopter will move into an unstable position. In other words, if the pilot takes a hand off the cyclic the helicopter is unable to maintain balance, which is especially dangerous in the event the pilot loses contact with the cyclic or otherwise becomes temporarily or permanently incapacitated. 
         [0074]    The present pressure jet propulsion system  34  rectifies these deficiencies by providing a mechanism for manually and/or automatically moving the mast mount assembly  28  longitudinally (shown) and/or laterally (in a similar left-to-right track system) in real-time to allow the mast assembly  30  to move over the center of gravity of the helicopter  10  so that the flight controls may be left in a neutral designated position for full range of motion and flight control. In this respect, the mast mount assembly  28  is movably carried by a rail system  166 , as shown best in  FIG. 6 , to permit manual and/or automatic adjustment or trimming of the mast assembly  30 . For example, as shown in  FIG. 6 , the rail system  166  permits longitudinal and latitudinal (with a similar perpendicular rail system) movement of the mast mount assembly  28  along a vertical axis designed to center the mast assembly  30  with respect to the center of gravity of the loaded helicopter  10 . More specifically, the rail system  166  includes, in a preferred form, a pair of rearwardly extending frame members  170  each having a linear rail  172  projecting therefrom in an inboard direction to fit into a pair of linear bearings  174  ( FIGS. 6 and 14 ) inserted into the mast mount assembly  28 . The linear bearings  174  ride on the linear rails  172  to accommodate fore-aft or longitudinal adjustment of the helicopter center of gravity, whereas latitudinal adjustment of the helicopter center of gravity is accomplished in a similar manner (not shown). Accordingly, longitudinal and latitudinal adjustment or trimming of the vertical axis of the mast assembly  30  is accommodated manually and/or automatically each time the helicopter  10  is loaded, according to the specific weight pattern of loading and the weight distribution of the occupants or the passengers  164 . In this respect, load sensors (not shown) in the seats and baggage area, load sensors on the landing gear mounting points, and fuel level sensors provide data feedback for computing the center of gravity and balance point of the helicopter  10  at any given point in pre-flight or during flight. A mast servo drive positioning system (not shown) is controlled by an on board central processing unit (CPU) which gathers and processes weight and fuel data to position the mast assembly  30  in real-time. A manually controlled positioning system may be included to back up the servo drive positioning system. 
         [0075]    In operation, trim of the helicopter  10  is manually made by the pilot or automatically achieved by an on board computer by moving the vertical axis of the mast assembly  30  over the specific center of gravity (CG) of the helicopter  10 . For explanation purposes, a substantially trimmed helicopter will have its floor substantially horizontal as the helicopter lifts off. If the CG of the helicopter  10  is forward of the mast assembly  30 , the helicopter  10  will be nose heavy and hang nose low at lift off. If the CG of the helicopter  10  is aft of the mast assembly  30 , the nose will be high at lift off. Likewise, the same holds true in the latitudinal axis. The CG in a helicopter is ever changing based on the number and weight of its pilot, passengers, baggage and fuel. In addition, most helicopters will normally become nose heavy as fuel is burned off in flight. Importantly, because counter-torque does not exist in a pressure jet propulsion driven helicopter, the need for a separate tail rotor and supporting bearings and the like are not required in the helicopter  10  of which uses the pressure jet propulsion system  34 , thereby also not requiring constant hands-on control by the pilot with continuous attention to the cyclic (for pitch and roll), collective and throttle controls (for altitude) to maintain proper flight altitude. The need for such constant control is greatly eliminated with the pressure jet propulsion system  34 , which offers a more relaxed and comfortable flight. 
         [0076]    Moreover, yaw control of the fuselage  16  of the helicopter  10  is controlled by deflecting the exhaust gases emitted from the engine housing  36  in a lateral direction with a tail rudder  176  or the like. When a piston or rotary engine is used as the power source, a portion of the compressed air can be directed through appropriate exhaust ducting  178  ( FIG. 4 ) to the rear tail rudder  176  to control the yaw movement of the helicopter  10 . Different types of engines, of course, can be used to power the compressor  26  such as conventional piston-driven or rotary gas-fueled engines, or a turbine engine which can run on diesel, kerosene or jet-A fuels. 
         [0077]    Seeing that the helicopter  10  is free of any counter-torque through use of the pressure jet propulsion system  34 , directional controls are smooth and positive, coordinated turns using a cyclic control stick and the rudder tail  176  are easy, and the helicopter  10  basically goes exactly where directed. From the perspective of a pilot, less training time is needed compared to a conventional tail rotor helicopter, and the overall skill level required to fly the helicopter  10  is greatly reduced. Accordingly, the pilot has more time to devote to precise and safer flying when counter-torque forces are absent. Thus, pilot reaction time increases in nearly all situations, thereby resulting in a greater degree of safety and control. 
         [0078]    Additionally, when making low speed and hover maneuvers close to the ground, conventional helicopters are put into a relatively more dangerous situation because of the generated counter-torque. Significant training and a tremendous amount of concentration is required to maintain control of the flight altitude of a conventional helicopter during landing maneuvers. In the case of the helicopter  10 , when the vertical rear tail rudder  176  is deflected, there is no effect on the engine power level or on the air flow delivered to the rotor blades  20 . This makes low speed and hovering much simpler and removes another pilot reaction requirement during close to ground operations - the single most critical phase in flying a helicopter. Also, the absence of a tail rotor eliminates inadvertent contact with the ground and other related injuries, such as striking bystanders on the ground. 
         [0079]    The inherent massiveness and mechanical integrity of the pressure jet rotor blades  20  is found in no other helicopter  10  of comparable size. Additionally, there is improved capability to jump-take-off with heavy loads. Another desirable feature of the pressure jet rotor principle is the relatively quiet operation as compared to a tail rotor helicopter. That is, a helicopter  10  utilizing the pressure jet propulsion system  34  will not experience the “whooping” sound as the blades rotate over the tail boom. 
         [0080]    The pressure jet propulsion system  34  is not only designed for new helicopter models, such as the helicopter  10  shown and described with respect to FIGS.  1  and  3 - 6 , but the system  34  can also be retrofit into existing helicopter designs, such as the helicopter  10 ′ (an MD600 Series helicopter) shown in  FIG. 35 . Preferably, the mast mount assembly  28  ( FIGS. 10 and 14 ) includes one or more connectors (not shown) that permit the mast mount assembly  28  to bolt into an existing airframe  300  at the main transmission mounting points already incorporated therein. The mast mount assembly is driven by a driveshaft  302  coupled to an engine  304 , such as an Allison C250-C47 808 shp Turbine Engine with FADEC. By attaching the mast mount assembly  28  to the already existing mounting points, the structural integrity of the helicopter  10 ′ does not change. To this end, the pressure jet propulsion system  34  may operate substantially as described above without extensive disassembly or reconfiguration of the helicopter  10 ′, thus providing a relatively easy and quick retrofit that attains some of the above-mentioned advantages, such as the desired light weight and greater payload capacity. 
         [0081]    Although several embodiments have been described in detail for purposes of illustration, various modifications may be made without departing from the scope and spirit of the invention. Accordingly, the invention is not to be limited.