IL35864A - Multiple helicopter lift system and a method for increasing its load transporting capacity - Google Patents

Description

liultiple helicopter lift system and a method for increasing its load transporting capacity ir? πκ*σ3Π n ia* n' an no'sn nonn tj»p¾oa naiyD naiyon Μτττ ιτρττ- ΗΤ-ττΓ^ Ρη τ ΤΤΡΓΠ nrnmnn^. ■ BACKGROUND OF THE INVENTION This invention relates to a system of connected helicopters that will provide a platform having a lifting capacity considerably exceeding that of a single helicopter. Regardless of what the lifting capacity produced by the latest and largest helicopter that comes off the production line may be, requirements always exist to lift loads beyond the capacity of that helicopter. This requirement for an increasing lifting capacity has resulted in the design and construction of ever larger machines but the capacity of these new machines has never caught up with the ever increasing requirement for a larger lifting capacity.

Much larger loads could be lifted if two or more helicopters were to be used in combination to lift more than either could lift alone. A scheme of this nature has been attempted wherein each of several helicopters have lifted one end of a spanning structure with the payload suspended or attached at the center of the structure. A further extension of this idea is to be found in U.S. patent No. 3,008,665 in which a further increase in lifting capacity is achieved by using a balloon in combination with the multiple helicopters. In this case the buoyancy of the balloon supports most of the empty weight of the helicopters so that all of the lifting capability can be applied to lift the pay-load rather than the structure weight.

In these examples each helicopter is operated as an individual entity. This system has a serious drawback in that, if any of the helicopters has a partial power failure, the entire system's lift capacity is drastically reduced because of the requirement for static equilibrium. For example, consider two heli erating at full power can lift 20 tons, including its own weight which may be 10 tons. The two, acting jointly, could lift 40 tons, 20 tons of which would be useful load. If one engine of one helicopter fails, however, that helicopter can only lift ap-proximately 1/2 its normal amount or 10 tons. Its payload capability would now be zero, instead of 10 tons. The other helicopter, in order to maintain equilibrium of the combination, would have to reduce to 1/2 power so that a safe useful load for the entire system, if engine failure is to be considered, is zero Another disadvantage of having each helicopter operate individually, is that each must be controlled by its own pilot and obtaining the necessary degree of coordination between the pilots of the separate helicopters is most difficult, requiring an exceptional degree of pilot skill and flawless communications.

An object of this invention is to provide an assembly of two or more helicopters that operate as an easily controlled integral unit to provide a lifting capacity greater than the individual helicopters.

Another object of this invention is to provide an assem bly of interconnected helicopters in which the failure of one or more engines of the various helicopters will not adversely affect the maneuverability or stability of the assembly nor disproportionately decrease the lifting capacity.

Yet another object of this invention is to provide an assembly of connected helicopters in which the attitude and vertical position of the entire assembly may be controlled from a single station. \ Yet still another object of this invention is t provide an integral assembly of connected helicopters having a large lifting capacity and being controllable from a single station in which all helicopters are of the conventional variety and upon being detached from the assembly can continue operating independently in a normal fashion.

SUMMARY OF THE INVENTION These objects have been achieved by providing a rigid structure for interconnecting two or more helicopters in a fixed, spaced-apart relationship, interconnecting the rotor drive systems of all helicopters so that the failure of any engine merely results in the loss of power of the one engine, and superimpos-ing on the basic control system of a designated master helicopter a coordinating transducer system that drives the actuators of various rotor control systems of all helicopters in such a manner that the rotational path and pitch of the individual rotors of each helicopter are coordinated to control the complete assembly of rigidly interconnected helicopters. Unlike the example discussed above of two jointly acting but independently operating helicopters, the lift system of this invention of two interconnected helicopters having three of the four engines operating could lift 3/4 of the original 40 tons, or 30 tons, of which 10 tons would be useful load.

BRIEF DESCRIPTION OF DRAWINGS Figure 1 is a schematic perspective view of one embodiment of the invention showing three tandem rotor helicopters rigidly connected together into an integral assembly to form a typical high lift system.

Figure 2 is a plan view of a portion of the assembly shown in Figure 1.

Figure 3 is a front elevation of that portion of the assembly shown in Figure 2.

Figure 4 is a schematic plan view illustrating the interconnection of the power trains of the embodiment shown in Figure 1.

Figures 5A and 5B are schematic diagrams of a typical manner of interconnecting the flight controls of the helicopters forming the embodiment illustrated in Figure 1.

Figures 6A, 6B and 6C are schematic front elevations of several embodiments of the invention illustrating various load hoisting arrangements for high lift systems.

Figure 7 is a perspective view illustrating another embodiment of the invention utilizing two interconnected, tandem rotor helicopters .

Figure 8 is a plan view illustrating still another embodiment of the invention involving two interconnected, tandem rotor helicopters,, Figure 9A is a view taken along section line 9-9 of Figure 2.

Figure 9B is a cross sectional view of a variation of one of the struts shown in Figure 9A„ Figure 10 is a schematic diagram of a manner of interconnecting the engine controls of a two helicopter lift system.

Figure 11 is a view similar to Figure 7 but illustrating a multiple helicopter lift system utilized in a towing operation, DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 is a schematic drawing illustrating a typical embodiment of the multiple helicopter lift system of this invention in which three tandem rotor helicopters 10, 11, 12 of conventional type and having conventional rotor, engine and power train and control systems are rigidly connected together into an integral assembly unit by the rigid beam structures 13, 14 of which the ends are each affixed to the fuselage structure of the respective helicopters by suitable attaching connections, such as bolts or the like. The individual interconnecting beam struc-tures 13, 14 can be of any convenient construction, such as the illustrated arrangement comprising the four struts 15 which attach to the fuselage structures of the respective helicopters through fittings (not illustrated) and separated by opposite pairs of horizontal and vertical struts 16, 17 extending transversely of the beam structure at spaced intervals along its length with structural bracing or wires 18 connected between points where the vertical and horizontal struts join. The beam structure is so configured and attached to the helicopters that there is clearance for the rotors, as may be seen in Figure 3 in which the center of the beam 13 is lower than each of the ends, as is the line of interconnecting power shafts 34. As illustrated in Figured, the structural members of the beam, such as the struts 15 can be of a streamline shape and their chords aligned such that the angle of attack of the streamline shape to the air flow during forward cruise speed would be a positive angle so as to add to the lift of the assembly in forward flight and also add to the span effect on the over-all lift to drag ratio of the assembly. Instead of being fixed, the streamlined struts can be made mounted in a manner that the direction of their chord is adjustable so that in towing or low speed operations the chord of the strut can be aligned with the air flow or at a small angle to the direction of air flow. Still another variation would be to make the rear portion of the streamlined strut rotatable with respect to the other portion in the manner of a single flap arrangement on an airplane wing in the general manner illustrated in Figure 9B in which the trailing edge portion 15a of the stream- lined strut is hinged at 15b. Of course, the front portion of the strut could also be mounted in a manner to be pivotable and further change the direction of the effective chord of the strut-Each beam structure with the drive shafting (to be subsequently described) attached thereto should be constructed in a manner to be readily transportable and easily attached and detached from the helicopter fuselage structure. Preferably the beam structure should be erectable in the field.

Each of the three helicopters 10, 11, 12 is a conven-tional type, tandem rotor helicopter having a front rotor system 19 and a rear rotor system 20 rotating in opposite directions and interconnected by a drive shaft 21 of the main rotor drive system which connects through a gear box 22 and cross shafts 23 to the two turbine engines 24, 25 that are each mounted opposite sides of the after section of the helicopter fuselage. Each helicopter is capable of operating independently in normal flight and, except for certain minor modifications involving beam structure attachment fittings, additional flight and engine control units and rotor drive system interconnecting gear boxes to be subsequently described, are standard helicopters capable of normal operations.

A minor modification to the rotor drive system of each helicopter is required to make it adaptable for use in the multiple helicopter system of this invention so that the rotor drive systems of all helicopters of the lift systems are interconnected causing the rotors of all connected helicopters in the assembly to rotate at the same speed and the engines to do likewise. Thus, if the engine of any of the helicopters should fail, it would cease to contribute power and merely result in a redistribution of the required power among the remaining operating engines. In each tandem rotor helicopter of the embodiment of Figures 1-3 an extra gear box may be installed in the manner illustrated in Figure 4 wherein the rotor drive shaft 21 of the center helicopter 11 is modified to install a supplementary gear box 26 in which the bevel gear 27 connecting to the rotor drive shaft 21 meshes with two bevel gears 28 each affixed to the end of a cross connecting shaft 29 extending outwardly on each side of the supplementary gear box. A supplementary gear box 30 is installed in the rotor drive system of each of the outboard tandem rotor helicopters 10, 12 with the gear box containing a bevel gear 31 con-nected to the rotor drive shaft 21 of each of the outboard helicopters and meshing with a bevel gear 32 connected to the end of a cross connecting shaft 33 that extends outwardly from the gear box in the direction of the center helicopter. Lengths of shafting 34 attach to and interconnect the cross connecting shafts 29 of the center helicopter 11 and the cross connecting shafts 33 of the outboard helicopters 10, 12 through flexible couplings 35. The interconnected lengths of shafting 34 are supported at spaced intervals in bearings mounted in brackets 36 that are supported at intervals along the top rear strut 15 of each of the beam structures 13, 14. As can be seen from Figure 4 the arrangement of the bevel gears in the gear boxes 26 and 30 is such that the rotor drive shafts 21 of all three helicopters rotate in the same direction„ The gear box arrangement of Figure 4, which is a schematic illustration only, shows the center helicopter 11 to have a supplementary gear box 26 that differs from the configuration of the gear boxes 30 of the outboard helicopters 10, 12. A standard supplemental gear box for all helicopters could be designed in which the gearing arrangement could be adjusted to suit any position that the helicopter might occupy in the lift system assembly.

The engine controls of each of the three helicopters are preferably interconnected so that they are all operable from a common master pilot's control station in one of the helicopters, to be discussed in more detail later with respect to flight controls, and the power output of all engines is equalized. Figure 10 represents one manner of interconnecting the engine controls of a lift system comprising two helicopters each having a single engine. Expansion of such an arrangement, or an equivalent arrangement, to the embodiment of three tandem rotor helicopters illustrated in Figure 1 is obvious to anyone skilled in the art. In the illustration of Figure 10 the right helicopter is the master helicopter from which the assembly of two helicopters is controlled from the pilot's station. A servo motor 6 or similar driving unit of a transducer system is connected to and actuated by the RPM control 5 of the right helicopter which also connects to and controls the engine speed of that helicopter through the usual engine governor and fuel controls, as illustrated. The servomotor 6 in the right helicopter has a suitable connection to a servo receiver 7 in the left helicopter, which receiver connects to and drives the RPM control 8 of the left helicopter, which also has the normal connections to control the engines of the left helicopter through its engine governor and fuel control units. Thus movement of the RPM control 5 in the master control, right helicopter not only establishes the RPM of the engine in the right helicopter but it also moves the RPM control 8 a similar amount, which movement is passed on to the governor and fuel control of the left helicopter. However, to overcome any slight amount of slack or variation in the transducer system and in the RPM control system of each helicopter, an arrangement that automatically equalizes the power output of the respective eng-ines in the two helicopters is indicated in Figure 10. A unit that adds the sum of the torques of all engines and determines the average torque output for each engine is installed in the right, or master, helicopter and a torque output signal from the engine of each of the helicopters is fed to this unit that is labeled a "Torque Summer", A "Comparator" unit is installed in each of the two helicopters and connections are made to the engine of that helicopter as well as to the "Torque Summer" with these connections, respectively, feeding to the "Comparator" from the engine a signal representing the engine output torque and a signal representing the average engine torque of all engines as measured by the "Torque Summer". Each "Comparator" then compares the two torque signals that are received and, if not the same, then feeds a signal through a connection to the fuel control of the helicopter in an amount to change the power output of the engine to match that of the other engine. The line diagram of Figure 10 is schematic only and it is to be understood that suitable feed-back and other necessary connections as are required to establish a fully operative system are visualized and considered to be a part of the system which a normally skilled power plant engineer can.produce. Although, such an interconnected engine control system as the one briefly described, or an equivalent, would make operation of the lift system more effective and easily controllable, the power output of the engine of the connected helicopters could probably be synchronized through the flight engineers or pilots in the respective helicopters adjusting the governor settings on the engines of the respective helicopters until the torque readings on each engine are the same. This would require constant communications and careful attention to the torque readings of the engines in order that no engine not contribute power to the system.

Since the interconnected helicopter system comprises a substantially single rigid structural assembly, preferably fea- tures are added to the flight control system that are additional to those found in the conventional system of each helicopter. These added features permit the flight path of the entire assembly of interconnected helicopters to be controlled from a single master station and also provide for actuating selected rotor control actuators that are not normally actuated by the normal movement of the conventional controls of the helicopter so as to generate a rotational path and pitch of selected rotors that will establish the additional moments and forces that are required to provide an adequate aerodynamic control for the entire assembly of connected helicopters,, The conventional cyclic pitch and rudder controls of each helicopter produce the necessary moments and forces required to control the attitude of the helicopter in roll, pitch and yaw. Although the forces exerted by the rotors of each of the three helicopters 10, 11, and 12 through the normal functioning of the cyclic pitch and rudder controls would, in general, be in a direction to establish the desired roll, pitch or yaw attitude of the entire assembly, these moments and forces in some instances would be of insufficient magnitude to effectively control the assembly of interconnected helicopters if the respective cyclic pitch and rudder controls of the three helicopters were merely interconnected and operated the respective rotor actuators of all three helicopters in the conventional manner. Therefore, it is proposed that the attitude control forces that are normally provided by movement of the attitude controls, i.e., the cyclic pitch control and the rudder control, be supplemented as indicated in the description to follow.

Table I, following, indicates the nature of control movement that may be applied to each rotor of each of the three tandem rotor helicopters of the embodiment of Figures 1-3 in executing the various indicated maneuvers that comprise the basic maneuvers required for flight control of the entire assembly of conventional helicopters and should be reviewed in association with the schematic diagrams of Figures 5 and 6 that illustrate the manner in which the flight controls are interconnected: TABLE I CONTROL INTERCONNECTIONS FOR MULTIPLE HELICOPTER LIFT SYSTEM TANDEM ROTOR HELICOPTERS TO MAKE MANEUVERS IN THE REVERSE DIRECTION, EACH CONTROL MOTION IN THE CHART IS REVERSED.

Table I indicates the control output required for each rotor helicopters, 10, 11, and 12 of Figures 1-3 in changing the lift of the helicopter or establishing the indicated attitude in roll, pitch and jaw. The major difference in the action of each of the controls, as compared to that of an individual helicopter in independent flight, is in the roll axis. The attitude of a single helicopter in roll is controlled by the lateral cyclic pitch. However, when three helicopters are connected together in the manner illustrated in Figure 1, the lateral moment of inertia of the rigid assembly of helicopters is so high that the moments established by the normal lateral cyclic pitch of the three individual helicopters would be insufficient for good control of the assembly of three helicopters about its roll axis. Superimposing a differential collective pitch change in the rotors of the outboard helicopters onto the usual lateral forces produced by moving the cyclic pitch control laterally creates a moment of the required magnitude about the roll axis of the assembly. Thus, for a roll to the left, the collective pitch of the rotors of the left helicopter 10 of the assembly are decreased and the collective pitch of the rotors of the right helicopter 12 are increased. The normal lateral cyclic pitch forces produced in each of the separate helicopters upon lateral movement of the cyclic pitch control is retained to provide a greater positioning precision in airborne operations.

The normal yaw forces produced in each of the helicop-ters by the rudder controls in establishing left and right cyclic control, respectively, to the front and rear rotors of the respective helicopters might be adequate for the assembly of three helicopters. However, if additional forces are desired to control the complete assembly in yaw, aft longitudinal cyclic con-trol can be superimposed on the rotors of a helicopter on one side of the assembly and forward longitudinal cyclic control can be superimposed on the rotors of the helicopter on the opposite side of the assembly upon movement of the rudder controls, as noted in Table I„ The pilot's station of one of the helicopters is chosen to be the master control station for controlling the flight operations of the integral assembly. This master control station can be the pilot's station of any of the three helicopters but in the embodiment of Figure 1 the master control station is indicated to be in the left helicopter 10. The reason for this choice, which is an arbitrary one, is that the pilot in the left hand helicopter would have a good overall view of the assembly of connected helicopters and the load L being supported by the lifting cable 37 from the center helicopter, as indicated by the two arrows extending from the window in the pilot's compartment of the left helicopter. As indicated, this choice of the master control station is an arbitrary one and could be in any of the three helicopters illustrated in Figure 1. If desired for safety purposes, a co-pilot's station could be incorporated in a helicopter other than the one in which the master control station is installed, such as either the center helicopter 11 or the right helicopter 12, or two co-pilot's stations could be incorporated so that one control station is installed in each of the three helicopters of Figure 1.

Figure 5A shows a typical manner of interconnecting the collective pitch controls and the lateral phase of the cyclic pitch controls of all helicopters and Figure 5B illustrates a typical manner of interconnecting the longitudinal cyclic pitch controls and the rudder controls in which all controls are actuated from the single master control station of the left heli-copter of the assembly. If a co-pilot's station is tc be incorporated, a servo system substantially duplicating that illustrat- ed for the roaster pilot's station would have to be provided and connected into the control system along with an interlock so that only the pilot's station or the co-pilot's station would feed an input into the controls of all helicopters at one time.

In Figure 5A the master cyclic pitch control and master collective pitch control of the left helicopter are shown in the top portion of the figure and the corresponding slave controls of the center and right helicopter are shown in the center and lower portions, respectively, of Figure 5. The conventional cyclic pitch control 38 of the left helicopter 10 has its normal connection to the actuators establishing lateral cyclic rotor control in the left helicopter, as indicated by the arrow and box labeled "Lateral Cyclic System". In addition, the left helicopter cyclic pitch control 38 connects through a mechanical, hydraulic, electrical or other connection 39 to a servomotor 40 or equivalent transmitting unit of a transducer system which in turn through a connection 41 of the servo system connects to and drives the servo receivers 42 and 43 in the center and right helicopter control stations, respectively., The servo receiver 42 of the center helicopter 11 connects through suitable linkages 44 or equivalent hydraulic, pneumatic or electrical connections to the cyclic pitch control 45 of the center helicopter which has its normal connection to the actuators establishing lateral cyclic rotor control in the center helicopter, as indicated by the arrow and box labeled "Lateral Cyclic System". Similarly the servo receiver 43 of the right helicopter 12 connects through suitable linkages 46 or equivalent connection devices to and drives the cyclic pitch control 47 of the right helicopter which has its normal connections to the actuators establishing lateral cyc-lie rotor control in the right helicopter, as illustrated by the arrow and box labeled "Lateral Cyclic System". Thus lateral mo- tion of the cyclic control pitch stick 38 in the master control station of the left helicopter, not only establishes lateral cyclic pitch in the rotors of the left helicopter 10, but also establishes the same lateral cyclic pitch dh the rotors of the cen-ter and right helicopters 11, 12.

In a similar manner the collective pitch control 48 at the master control station in the left helicopter 10 has suitable connections represented by the linkages and connections 49 to a servomotor 50 of a servo or transducer system with connec-tions 51 to the servo receivers 52 and 53 which connect through suitable linkages 54, 55 or other type connections to the collective pitch controls 56 and 57 of the center and right helicopters 11, 12, respectively.

The collective pitch control 56 of the center helicop-ter 11 has its normal connection to the actuators establishing collective pitch rotor control in the left helicopter, as indicated by the arrow and box labeled "Collective Pitch System". However, in the left and right helicopters the motion of each of the respective collective pitch controls 48, 57 is transmitted to the rotor collective pitch actuators of these helicopters, of which the normal connections are represented by the arrows and boxes labeled "Collective Pitch System1', through a motion integrating unit 58, 59. The motion integrating unit 58 of the left helicopter control system adds the motion produced by a servo receiver 60 connected by the servo system line 61 to the servomotor 40 in the servo system of the lateral cyclic pitch control to the normal control motion fed to the collective pitch system of the left helicopter by the linkages 65 from the master collective pitch control 48. Thus the collective pitch of the rotors of the left helicopter is established by motion of either or both the master collective pitch control 48 and lateral movement of the master cyclic pitch control 38. Similarly, the motion integrating unit 59 in the right helicopter has an output to the actuators in the collective pitch control system of the right helicopter that reflects both any motion imparted by the servo receiver 62 driven by connections 63 from the output of the lateral cyclic pitch servomotor 40 and the normal control motion fed to the collective pitch control system and motion integrating unit 59 by the linkage 64 of the master collective pitch control 48. The motion integrating units 58 and 59 can be of any conventional type of device, mechanical, electrical ,. hydraulic or otherwise in which motion from one source is added to that of another source such as any conventional extensible link arrangement, a differential worm gear arrangement, a whiffletree, etc. To comply with the requirements of Table I, the direction of movement induced in the servo receiver 60 of the integrating unit 58 in the left helicopter 10 by movement of the lateral cyclic control 38 must be opposite that of the movement induced in the servo receiver 62 of the integrating device 59 of the right helicopter 12 so that lateral motion of the master cyclic pitch control 38 will establish an increase in collective pitch of the rotors of one outboard helicopter and a decrease in collective pitch of the rotors of the opposite outboard helicopter.

The placement of the controls of each of the three helicopters in Figure 5B is the same as in Figure 5A, the con-trols at the master pilot station in the left helicopter being at the top of the figure. The conventional rudder control 66 of the left helicopter has its normal connection to the actuators establishing yaw control in the left helicopter as indicated by the arrow and box labeled "Yaw Control System". In addi-tion the left helicopter rudder control 66 connects through a linka e 67 or other suitable h draulic electrical or other t e connections to a servomotor 68 which in turn connects through the connection 69 of a servo or transducer system to and drives servo receivers 70 and 71 in the center and right helicopters, respectively. The servo receivers 70, 71 each are connected through suitable connections 67 ' , 67 ' 1 to drive the rudder controls 72 and 73 in the respective center and right helicopters, which in turn have their normal connections to the actuators establishing yaw control in the helicopters as indicated by the arrow and box labeled "Yaw Control System". Thus the various actuators of the rotors in all helicopters that establish normal yaw control in the helicopters in their normal, independent flight mode follow the rudder control 66 in the master station of the left helicopter.

Control of the assembly in pitch is exercised through the cyclic pitch control 38 in the master helicopter. A servomotor 74 connects through suitable linkages and other type connections 75 to the cyclic pitch control 38 of the left helicopter (master station) in a manner to be actuated by longitudinal motion of the left helicopter cyclic control 38 in the same man-ner as the servomotor 40 is actuated by lateral motion of the cyclic control 38 „ The longitudinal cyclic servomotor 75 connects to and drives servo receivers 76 and 77 through a suitable connection 78 and the servo receivers 76 and 77 operatively connect through linkages 79 and 80 or other type connections in the respective center and right helicopters to the cyclic pitch controls 45 and 47 of these helicopters in a manner that the "slave" cyclic pitch controls 45, 47 of the center and right helicopters have the same longitudinal motion as that of the master cyclic control 38 in the left helicopter,, In the particular embodiment illustrated in Figure 5B the longitudinal phase of the cyclic pitch control 45 in the establishing normal longitudinal cyclic rotor control in the center helicopter but the output of the longitudinal phase of the left and right helicopter cyclic pitch controls 38 and 47 does not directly connect to the normal longitudinal cyclic rotor control systems of these helicopters but connects to these control systems through motion integrating units 81 and 82 in a manner similar to the arrangement of the collective pitch controls 48 and 57 of the left and right helicopters. The motion integrating units 81 and 82 each respectively incorporate a servo receiver 83 and 84 that respectively connect through suitable connections 85 and 86 to the output connection 69 from the rudder control servomotor in the left helicopter so that the servo receivers 83 and 84 receive signals upon actuation of the master rudder control 66. Each respective motion integrating unit 81, 82 is connected by a linkage 87, 88 to the cyclic pitch controls 38, 47 of the left and right helicopters, respectively, so as to transmit to the actuators of each of the longitudinal cyclic rotor control systems of the left and right helicopters, indicated by the arrow and box labeled "Longitudinal Cyclic System", the combined motion established by the servo receiver and its associated linkage actuated by longitudinal motion of the respective helicopter cyclic pitch controls,, The arrangement of the motion integrating units 81 and 82 and the associated servo receivers and connections is such that the respective servo re-ceivers 82 and 84 feed oppositely directed signals or motions to the respective integrating units so that movement of the master rudder control 66 in a given direction will establish oppositely directed longitudinal cyclic pitch in the rotors of the left and right helicopters, respectively, thus establishing oppositely directed longitudinal cyclic pitch in the rotor systems of the left and right helicopters in the alternate manner indicated in the last column of Table I. In other words the rotor system of the left helicopter 10 would establish a longitudinal cyclic pitch force in one direction and the rotor system of the right helicopter 12 would establish a longitudinal cyclic pitch force in the opposite direction upon actuation of the master rudder control 66. If the yawing moment produced on the entire assembly of interconnected helicopters by the normal yaw forces that would be established by the individual helicopters upon actuation of their individual rudder controls would be adequate, the longitudinal cyclic motion integrating units 81 and 82 and the respective associated servo receivers 83 and 84 and connections 85 and 86 could be eliminated, so that the connections of the longitudinal phase of the cyclic pitch controls of the left and right helicopters would be the same as shown for the center hel-icopter in Figure 5B.

Although the diagrams of Figures 5A and 5B illustrate stick type flight controls and mechanical link connections, it should be understood that electrical type controls or equivalent arrangements could be utilized. The servo or transducer system and connections are also schematically indicated with no feed back connections shown „ However, it should be understood that any type transducer or servo system could be utilized to accomplish the control interconnections indicated in Table I and that suitable feed back and other types of necessary or desirable con-nections are contemplated. Although the interconnection of controls herein described is desirable and permits the multiple helicopter system to be controlled by a single pilot, it is probably possible for a team of well trained pilots to control such a system from the normal pilot's station in each helicopter, if pro-vided with adequate communications. types could also be rigidly interconnected by a beam arrangement similar to that illustrated in Figures 1-3 for providing a lift system. However, tandem rotor helicopters appear to be somewhat more adaptable for use in this invention than single rotor helicopters or other types as the drive shaft arrangement of the tandem rotor helicopters presents less of a problem in interconnecting the rotor drive systems of the helicopters. The manner in which controls of single rotor type helicopters could be interconnected in order to achieve satisfactory aerodynamic control of the entire assemblage of interconnected single rotor helicopters from a single pilot's station is outlined in Table II to follow. The arrangement of servo system and interconnection of the controls to achieve the rotor control forces outlined in Table II could be generally similar to the arrangement illustrated in Figure 5 modified to a single lifting rotor configuration for each helicopter and will not be described since it would be obvious to one normally skilled in the art. Therefore, it should be understood that whenever this specification or claims refer to the term "rotor" the plural is also intended where appropriate.

TABLE II CONTROL INTERCONNECTIONS FOR MULTIPLE HELICOPTER LIFT SYSTEM ( SINGLE-ROTOR TYPE HELICOPTERS) INCREASE PITCH ROLL YAW* MANEUVER TOTAL LIFT NOSE DOWN LEFT NOSE LEFT INCREASE COL- FWD.LONGI- LEFT LATERAL CONVENTIONAL LECTIVE PITCH TUDINAL CYCLIC AND SINGLE ROTOR LEFT INCREASE TAIL CYCLIC DECREASE YAW CONTROL HELI- ROTOR PITCH PITCH COLLECTIVE AND/OR AFT COPTER(S) TO BALANCE PITCH LONGITUD.

TORQUE CYCLIC PITCH INCREASE COL- FWD.LONGI- LEFT LATERAL CONVENTIONAL LECTIVE PITCH TUDINAL CYCLIC SINGLE ROTOR CENTER INCREASE TAIL CYCLIC YAW CONTROL HELI- ROTOR PITCH PITCH COPTER TO BALANCE TORQUE INCREASE COL- FWD.LONGI- LEFT LATERAL CONVENTIONAL LECTIVE PITCH TUDINAL CYCLIC AND SINGLE-ROTOR RIGHT INCREASE TAIL CYCLIC INCREASE YAW CONTROL HELI- ROTOR PITCH PITCH COLLECTIVE AND/OR FWD.

COPTER(S) TO BALANCE PITCH LONGITUD.

TORQUE CYCLIC TO MAKE MANEUVERS IN THE REVERSE DIRECTION, EACH CONTROL MOTION IN THE CHART IS REVERSED.

* Yaw may be controlled by locking out the tail rotor in minimum pitch and controlling yaw by utilizing oppositely directed longitudinal cyclic control on the two outer helicopters, thus reducing tail rotor power losses. In addition, the anti-torque requirement could be satisfied by the same arrangement of differential longitudinal cyclic control of the outboard heli- copters or by connecting the outboard helicopters to offset the rotors from the vertical in opposite directions.

Although the previous discussions and the illustrations of Figures 1-5 relate to an assembly of three interconnected helicopters, the multiple lift system could obviously comprise two helicopters or four or more interconnected helicopters. Figure 7 illustrates an arrangement wherein two tandem rotor helicopters 90 and 91 are interconnected by a single beam structure unit 92 which can be of the same general type as the beam structures 13, 14 previously briefly described with respect to the arrange-ment of Figure 1. The rotor drive systems of the two helicopters, of course, must be interconnected through a suitable shafting arrangement 93 in a manner generally similar to that previously discussed relative to the embodiment of Figure 1 and the controls of the two helicopters must be integrated in a manner somewhat similar to that of the three helicopter embodiments illustrated in Figure 1 with the controls in one of the helicopters driving the rotor controls of both helicopters and an interconnection being provided between the lateral cyclic control and the collective pitch control so that differential collective pitch control is established to provide for effective control of the entire assembly about its central roll axis. Differential longitudinal cyclic pitch control can also be tied into the rudder about its yaw axis, as in the case of the embodiment of Figure 1. In the two-unit multiple lift system illustrated in Figure 7 the hoist cable 94 attached to the load L cannot be supported from the fuselage structure or a winch in one of the helicopters but must be supported from the beam structure 92 at a midpoint between the two helicopters 90 and 91.

Another possible arrangement of two helicopters is illustrated in Figure 8. In this embodiment two tandem rotor helicopters 100 and 101 are arranged in a side-by-side relation-ship but facing in opposite directions, the fuselage structure of the respective helicopters being rigidly interconnected by an X beam arrangement 102 or any other type of rigid beam structure arrangement. As in the previously described assembly of tandem rotor helicopters, the rotor drive shafts 103 of the two helicopters are interconnected by suitable gear boxes 104 and interconnecting lengths of shafts 105. This particular embodiment of Figure 8 has an advantage in that the separation between the two helicopters 100, 101 can be less than that for the previously described embodiments of tandem rotor helicopters. In the embodiment of Figure 8 the span of the front rotor of one heli-copter can overlap the span of the rear rotor of the other helicopter since the blades of the overlapping rotors are moving in the same direction so that they can intermesh like the blades of an egg beater. The span of the front rotor 106 of helicopter 100 in Figure 8 overlaps the span of the rear rotor 107 of the other helicopter 101 in Figure 8 and the span of the rear rotor 108 of the helicopter 100 in Figure 8 overlaps the span of the front rotor 109 of the other helicopter 101 in that figure, the arrows on the circular arcs representing the respective rotor spans in-dicating the direction of blade movement. In this embodiment the such that there is blade clearance between the front rotors 106 and 109 and the rear rotors 107 and 108 of the respective helicopters. Although the interconnection of the controls of the two helicopters in the embodiment of Figure 8 is not quite as simple as that in the embodiment of Figure 7, interconnection of the controls of the two helicopters through transducer systems in establishing the necessary forces and moments to control the entire assembly in roll, pitch and yaw is obvious from the descriptive matter relating to the interlinkage of the controls in the embodiment of Figures 1 and 7. For example, in interconnecting the longitudinal cyclic controls of this embodiment, a reversal of control movement direction would have to be incorporated since the two helicopters are facing in opposite directions. However, this could be easily incorporated when installing the transducer system.

Although all discussions have related to a multiple helicopter lift system in which the helicopters are arranged in a side-by-side arrangement, the helicopters could be interconnected with each other in a tandem arrangement, a V-type arrange-ment or any other geometrical pattern that might be considered to be advantageous. Of course, the manner in which the rotor controls are interconnected to provide for an integration of collective pitch control into cyclic pitch control or possibly the integrating cyclic pitch control into rudder control in es-tablishing the required moments and forces to control the entire assembly in roll, pitch and yaw would be different than the interconnections indicated in Tables I and II if the helicopters were not connected in a side-by-side arrangement. For example, if the helicopters were connected in a tandem arrangement, dif-ferential collective pitch control would have to be integrated into the lon itudinal c clic itch control to establish the nec- essary moments of the entire assembly in pitch and the normal lateral cyclic pitch control of the individual helicopters would be adequate for controlling the attitude of the assembly in roll.

Since the multiple helicopter lift system is visual-ized as being essentially a flying crane, provisions should be included for attaching to the load to be lifted. Figures 6A, 6B and 6C are schematic diagrams indicating possible ways for controlling the load lifting arrangement of the assembly of helicopters. Figures 6A and 6B relate to the embodiment of Figure 1 in which the three helicopters 10, 11 and 12 are interconnected by the beam structures 13 and 14 previously described. In the embodiment of Figure 6 winches 110 are installed in each of the three helicopters 10, 11 and 12. Lifting cables 111 for each of these three winches can be reeved through a suitable pulley sys-tern with a suitable load limiting device on each to converge at the center helicopter 11 for attachment to a single lifting hook 112 so that a load to be lifted by the entire assembly is shared by the lifting cables of the three winches 110. In such an arrangement provisions can be made for interconnecting the controls for the three winches so that one control would operate all three winches. In the arrangement of Figure 6B but a single winch 113 is installed in the central helicopter 11. Figure 6C shows an arrangement for a single winch 114 installed in the connecting beam structure 92 of the dual helicopter arrangement of Figure 7. In such a dual arrangement it would also be possible to utilize individual winches installed in the respective helicopters 90 and 91 with the winch cables reeved through a suitable pulley system, similar to that illustrated in 6A, to converge at the center of the beam structure 92 for attachment to the load lift-ing hook or structure. multiple helicopter lift system that is operating in the general nature of a flying crane in which the load from the helicopter assembly is supported by a cable extending vertically below the center of the assembly, many other arrangements for supporting a load could be provided. A load could be hoisted onto and affixed to the lower part of the helicopter interconnecting frame structure or could even be integrated into the connecting structure itself. Many variations of attaching the load to the assemblies of helicopters comprising the multiple lift system could be adopted. Helicopters are used, not only for lifting and transporting loads by air, , but also for towing vehicles or objects on land or water. As an example, they are used for towing mine sweeping gear, where they have the advantage of not, themselves, detonating the mines in the swept path, a constant threat to mine sweeping vessels. The multiple helicopter lift system has the same potential for towing greater loads as for lifting greater loads. Utilization of the multiple helicopter lift system for towing purposes is illustrated in Figure 11. In this drawing, the two helicopters 90 and 91 are interconnected by an arrangement similar to Figure 7 and a tow line 115 leads from the center of the connecting beam 92 to the device which is being towed beneath the water. Obviously the equivalent towing arrangement could be utilized to tow items across the surface of the water or on land.

It should be understood that the foregoing disclosure relates only to typical embodiments of the invention and that numerous modifications or alternations may be made therein without departing frbm the spirit and the scope of the invention as set forth in the appended claims.

Claims (3)

1. Claims; ΐι· An Integral aerial lifting system comprising a plurality of separate aircraft vertical lifting units each having a powered rotor lifting system and a flight control system having a collective pitch control system actuated by a collective pitch control and an attitude control system actuated by at least one attitude control, means for rigidly connecting said units together in a rigidly fixed, spaced-apart relationship to form an integral assembly, means interconnecting the flight control systems of all said units for actuating the collective pitch and the attitude control systems of all units upon actuating the collective pitch and attitude controls of one of said units and means for interconnecting the power system driving the rotors of each of said units to cause the lifting rotors of said connected units to rotate at the same speed*

2. * The aerial lifting system of claim 1 additionally comprising means operable upon actuation of an attitude control of said one unit for causing a differential actuation of the collective pitch control systems of two units oppositely located with respect to said connecting means*

3. * The aerial lifting system of claims 1 or 2 wherein said connecting means connects said units in tandem and said differential collective pitch actuation means is operable to establish a differential collective pitch in the rotors of said oppositely connected units upon actuation of said one unit cyclic pitch control in the pitch phase* h* The aerial lifting system of any one of claims -f o 2 wherein said connecting means connects said units in jjuxtaposition and said differential control pitch actuation means is operable to establish a differential pitch In the rotors of said oppositely connected units upon actuation of said one unit cyclic pitch control in the roll phase* 5· The aerial lift system of any one of claims 2 to k wherein the attitude control system of each unit includes means controlling the pitch of the rotor blades cyclically to control said unit in roll and pitch and Baid attitude control includes a cyclic pitch control* and said means for causing differential collective pitch actuation includes an operative connection between the cyclic pitch control of said one lifting unit and the collective pitch control system of each of two connected units located on opposite sides of a mid-point between the most widely spaced of said connected units, said means for cyclically controlling the pitch of the rotor blades of said two units and said operative connection being arranged such that movement of said one cyclic pitch control of said one unit in a given direction causes the collective pitch control, systems of each of said two oppositely located units to change the pitch of the rotor lifting blades of the respective units In opposite directions, thereby increasing the pitch of the rotor lifting blades of a unit on one side of said mid-point and decreasing the pitch of the rotor lifting blades of a unit on the other side of said midpoint to establish a moment about a pitch or a roll axis of said integral assembly* 6· The lift system of any one of claims 2 to 5 wherein the attitude controls o said one unit additionally include a rudder control for controlling yaw and the rudder of said one unit control operatively connects to the means for cyclically controlling the pitch o the rotor blades of the two oppositely located li ting units, said rudder control connections being arranged such that movement of the rudder control of said one unit in a given direction causes the rotor cyclic pitch control system of each of said two oppositely located lifting units to change the pitch of the lifting rotor of the respective units in an opposite manner to establish a moment about the yaw axis of said integral unit* 7· The lift system of any one of claims; 2 to 5 wherein said attitude control of said one unit includes a yaw control, the attitude control system of said one unit is operatively connected to the pitch actuator of a tail rotor such that movemen of said one helicopter yaw control causes the pitch actuator of said tail rotor to change pitch establishing a moment about the yaw axis of said integral assembly. 8. The aerial li ing system of claim 1 wherein said vertical lifting units are helicopters, the flight control system of each said helicopter includes a rotor collective pitch control system operable by the pilot's collective pitch control, a rotor cyclic pitch control system operable by the pilot's cyclic pitch control and a yaw control system operable by the pilot's rudder control, and said flight system 3586V23A interconnecting means includes means connecting to the pilot's collective pitch control of one of said helicopters and the collective pitch control systems of all other of said helicopters for operating the collective pitch control eystems of all said helicopters by actuating the collective pitch eontrol of said one helicopter, means connecting to the pilot's cyclic pitch control of said one helicopter and the cyclic pitch contro systems of each of the other of aaid helicopters for operating the cyclic pitch control systems of all said helicopters by actuating the cyclic pitch control of said one; helicopte » means connecting to the pilot's rudder control of said one helicopter and the yaw control systems of each said other helicopter for operating the yaw control systems of all said helicopters by actuating the rudder control of said one helicopter, and means connecting to the cyclic pitch control of said one helicopter and the collective pitc control systems of each of at least two connected helicopters located on opposite sides of a mid*point between the most widely spaced of said connected helicopters for causing the collective pitch of the rotor system of one of said oppositely located helicopters to increase and the collective pitch of the rotor system of the other of said oppositely located helicopters to decrease upon actuation of the cyclic pitch control of said one helicopter* 9· The aerial lift system of any one of claims 1 to 8 wherein said connecting means includes horizontally extending structural members connecting between adjacent 3586W3 lifting units, said structural members being streamlined in shape and being positioned at such an angle as to establish a positive angle of attack to the airflow during forward motion of said integral unit at cruise speed* 10· The aerial lift system of any one of claims 1 to 8 wherein said connecting means comprises a beam structure having connections at each end adapted for connecting to the structure of one of said helicopter units and attaching means for rigidly connecting said connection at each of said beam structure to a different helicopter. said beam structure including horizontally extending structural members having a streamlined shape and positioned such that the chord of said streamlined shape is positioned so as to establish a predetermined angle to the airflow during the forward flight motion of said assembly* 11· The lift system o claim 10 wherein at least some of said attaching means are adapted for adjusting the direction of the chord of said streamline structural members. 12· The lift system of claim 11 wherein at least some of said streamline structural members are divided into at least two segments and include means for changing the relative alignment of said two segments* 13· A method of providing a load transporting capacity greater than the transporting capacity of a single helicopter operating independently comprising the steps of rigidly connecting together BK in a fixed, spaeed-apart relationship a plurality of helicopter units each having a flight control system tha includes a rotor collective pitch control system operable through a collective pitch control means and an attitude control system operable through an attitude control means that includes a cyclic pitch control means, thereby establishing a rigidly connected assembly of helicopter unite, a lyi g the load to said assembly of helicopter units, operating the rotor drive systems of said connected helicopter units as a single system at the same RPM by interconnecting the rotor drive systems of all said connected helicopter units, and controlling the flight control system of each said helicopter unit of the assembly by operating the collective pitch control systems of all said helicopter units through the collective pitch control means of one of said connected helieopter units and by operating the attitude control systems of all helicopter units through the attitude control means of said one helicopter unit. 1 « The method of claim 13 wherein operation of said attitude control means of said helicopter includes operation of said cyclic pitch control means of all helicopters by operating the cyclic pitch control of said one helicopter unit and causing the collective pitch of the rotor system of one of at least two of the connected helicopter units located on opposite sides of a midpoint between the most widely spaced of 3586 3A the rotor system of the other of said oppositely located helicopters to decrease upon actuation of the cyclic pitch control of said one helicopter unit in controlling attitude along the direction of alignment of said oppositely located helicopter units. 15· An integral aerial lifting system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. 16 A method of providing a load transporting capacity greater than the transporting capacity of a single helicopter operating independently as claimed in claims 13 and ih substantially as hereinbefore described. or App can s