Nov. 2, 1965 R. M. sTEFHENS 3,215,366 5 sheets-Sheet 1 Filed May 16, 1963

NVENTOR Nov. 2, 1965 R. M. STEFHENS 3,215,366 ROTORCRAFT Filed May 16, 1963 5 Sheets-Sheet 2

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| NVENTOR 3,215,366 United States Patent Office Patented Nov. 2, 1965

2 3,215,366 the turbo-propellers its rotor is then in the unloaded con ROTORCRAFT Robert Melling Stephens, 296 Matheson Ave., Winnipeg, dition, that is, without benefit of power and consequently Manitoba, Canada autorotates, but still contributes 50 percent of the lift. Fided May 16, 1963, Ser. No. 280,804 occurs because of a natural imbalance of 11 Claims. (C. 244-7) drag between the advancing and retreating blades in trans At the present time the only capable of operat lational flight. The retreating blade having its back to ing city-center to city-center in the short haul range, e.g., the wind, so to speak, has the greater drag. With the 200 to 300 miles, is the . Its relatively low four-bladed rotor of the second embodiment of present speed of 175 miles per hour coupled with a high passenger invention this condition still exists but to a much smaller mile operating cost are its chief drawbacks. In 1957 the O degree, by design generating just enough centrifugal force Fairy “Rotordyne” which operated somewhat along heli in the unloaded condition to counteract blade flutter. copter lines underwent a series of tests. It was designed However, with the two-bladed rotor of the first embodi to remedy particularly the high passenger-mile operating ment having a wider chord and greater depth there is cost of the helicopter, which it did very successfully but greater rigidity in the blades and the necessity to auto brought in its wake its own problems, chiefly noise, hot 15 rotate when in the unloaded condition is absent. In trans oil splattering and excessive vibration. These difficulties lational flight the rotor would be halted and secured in were never fully overcome and it was finally abandoned the transverse position lying directly above the fixed wings in 1962. and so becomes a secondary airfoil. The distinguishing Conventional high speed fixed wing airliners require design feature of the blades is that the upper surface is for take-off a mile-long runway, which is not available 20 highly cambered and symmetrical and thus generates lift in city-center; and if vertical-take-off-and-landing (VTOL) consequent upon air flow from either direction whether characteristics could be given to this type of aircraft, such rotating or locked. This is a unique feature basic to the improvement would be without parallel in the history of invention and is believed to represent a new concept in aviation. rotor design. With a conventional airfoil profile, for It is in this short-haul 250-mile range that the type of 25 instance, and with the blades locked in the transverse posi aircraft like the Vickers “Viscount” propelled by turbo tion, one blade would provide lift while the opposite blade prop finds its niche, and while its speed is no would record a negative lift force. match for the turbo-jet it has a cruising speed 2/2 times It should be noted that the blades in all embodiments that of the helicopter including the Fairy “Rotordyne.' herein described have their chord line in line with the Its lower wing loading compared with turbo-jet would be 30 plane of rotation, consequently have in themselves no of great assistance if VTOL characteristics could be ap angle of attack, yet create lift. This lift is further in plied. creased and uniformly so on all blades operating in trans Present invention seeks to retain all the advantages of lational flight by giving a fixed angular elevation to the this turbo-prop aircraft and couple with it VTOL charac plane of rotation at the pylon to the same degree possessed teristics. In appearance however the type of craft in 35 by the lower fixed wing, possibly 3 degrees. At this angle vented resembles the Fairy “Rotordyne” which incidentally the lift on this type of blade is considerably enhanced and is different from the helicopter only in that the Rotordyne the high drag on the blades somewhat compensated, with has in addition a fixed wing of short span in the high wing the rate of autorotation being regulated by the design of position carrying half the total load, while the other half the lower camber. In the embodiment having the four is carried by the rotor. On the other hand a helicopter 40 bladed rotor the lower blade contour will resemble the rotor carries all the load all the time. lower surface of the standard wing profile N.A.C.A. 23012 In the present invention the fixed wing is dimensioned while the two-bladed rotor, likewise a three-bladed rotor, to carry approximately 90 percent of the load and its if used, would have its lower surface flat except at the rotor the 10 percent balance. The percentages relate of nose and trailing edge which would be rounded off. The course to translational (forward) flight at cruising speed, 45 lower surface of the N.A.C.A. 23012 is unsymmetrical while in vertical-take-off as in landing the rotors would and the drag on it would be slightly greater when its sustain all the load. The difference between the rotor of back was to the wind, consequently would autorotate the Rotordyne and the present invention is one of function slightly when unloaded. as well as design, and as a contingent consequence the With the Fairy “Rotordyne” means were incorporated aircraft requires a change in configuration from the high 50 to obtain collective adjustable pitch whereby all four wing position of the Rotordyne to the low wing position, blades could be given a uniform angle of attack which for reasons to be explained later. in the VTOL regime provided equal lift on all four blades. At this angle the blades of the 90-foot diameter rotor have The Rotordyne acquired its excellent VTOL character a co-efficient-of-lift maximum of 1.4 and at maximum istics by means of a fuel-fired jet at the tip of its enormous 55 revolutions provided a rate of climb of 1600 feet per 90-foot diameter four-bladed rotor. These are the tip jets minute. responsible for the hot oil splattering; and being located With the present invention no such manipulation is right at the wing tip, some of the fuel escapes unburnt. necessary, the blades deriving their great lift by an entirely They were also responsible in operation for most of the different principle to be explained later. From 5 to 7 noise. These jets were Supplied with highly compressed 60 times more lift per square foot of blade area can be air ducted from a pair of turbo-prop engines located out generated depending on the mass of compressed air made board under the fixed wings of the aircraft astride the available for ejection at the trailing edge. Obviously fuselage. under proposed regime a much smaller diameter rotor is In cruising flight the Rotordyne being driven solely by needed for the same lift, with all the accruing advantages. 3,215,366 3. 4. The two blades of the rotor of this invention as depicted coming slipstream below, reversing the natural flow at in the first embodiment are divided chordwise into a front the trailing edge. With this modification and the use of portion and a rear portion. The rear portion receives this cold air instead of hot exhaust a C max. 7.5 could be compressed cold air ducted via the pylon from the turbo anticipated. The type of slit illustrated in 2.13b of course prop compressor located on the wings and because of the was devised to produce the required lift without the un high pressure involved must be contained within ducts desirable forward thrust previously mentioned when as having a cylindrical form, from which it is ejected through sociated with the fixed wing but this would be no detri a series of narrow slits at intervals running the length of ment to a rotating blade, consequently the arrangement the blade adjacent to the trailing edge, as well as from illustrated in 2.13a or a compromise with 2.13b would a jet at the tip of the blade. O lend itself to better advantage provided the jet on the The front portion of the blade forms a series of longi underside were moved forward sufficient to bring the tudinal ducts along which flows the large mass of ambient center of pressure (lift) midway of the chord. If this is air entering at the top of the camber at the hub to be not done the blade will twist and the lift will be greatly centrifuged by the rotation of the blades then, heated and lessened. It will also be necessary to vary the angle of exhausted at the tip to provide propulsion. The com 5 the jet sheet in accordance with the variation in velocities bustion chambers are placed at a distance of 3 feet ap as they exist from the root to the tip of the blade as it proximately from the tip of the blade to ensure that the rotates. When in full VTOL operation the tip of the fuel is fully burnt. rotor blade may be moving at a speed of 800 feet per Initially the compressed air will be directed to one of second yet only 133 feet per second at the 5-foot radius the tip jets to start the blades rotating and when the 20 mark, consequently the horizontal deflection of a jet sheet revolutions of the rotor have increased to the point where having a fixed efflux angle and a uniform velocity will ambient air would be sufficiently centrifuged to support vary greatly at these two points because the impact of the combustion, centrifugal force opens up the fuel supply wind on the jet sheet as it moves in its circular course to the fuel burners and at the same time a flap-valve will vary as the square of the velocity. While these facts under the action of a weight functionally centrifugally 25 are valid in themselves it is also well known that 85 closes of the supply of cold compressed air to the tip, percent of the thrust of a is performed by the when it is then constrained to exhaust from the spanwise outer half of the blade, which would indicate that to slits at the trailing edge to create lift. As the centrifugal economize on air flow the spanwise slits should be con force increases with the increased rotation of the rotor fined to the outer 60 percent of the blades. so does the fuel supply, and the power potential of the 30 Without indicating the relative velocities, Smoke tests centrifuged ambient air becomes self-propagating limited in the wind tunnel reveal that as one consequence of this by the amount of fuel it is found expedient to burn. Much high lift phenomenon, demanding at great cost in power, addition power is thus made available to rotate the blades. sonic velocity in the air jet sheet, the whole mass of at To a certain extent the design and location of the span mospheric air flowing over the upper and lower surface wise slits will follow the pattern laid out in illustrations 35 of the blade is diverted almost vertically downward 2.13a and 2.13b on page 23 of "Flight Handbook,' 6th whereas with the C max. 1.4 of the Rotordyne blade the edition, published in 1961 by Aero Publishers Inc., Los air mass is only deflected some 10 degrees. This vertical Angeles. Illustration 2.13a shows a single jet sheet di deflection of the air mass in considerable depth is the rected vertically downward from the lower camber near reason previously intimated I consider it essential to lo the trailing edge of the wing where, functioning in the 40 cate the fixed wing of this rotorcraft in the low wing po manner of a Fowler flap, it produces this high lift as the sition so as to reduce interference of the low wing with wing moves forward. This jet sheet has the disadvantage the jet sheet as much as possible. The difference in the however by reason of its deflection to the rear of pro two wing positions could amount to 8 feet or more. ducing additional thrust which if applied to the wing of In spite of the extremely high lift generated, VTOL a conventional airplane would be an undesirable factor. 45 benefits cannot be conferred by this means on the fixed It is a primary necessity to reduce speed for landing, not wing of a conventional aircraft since a high velocity cir increase it. culatory flow over and under the wing is necessary and The concept of the jet flap had its beginning many years this can only be obtained by a forward movement of the ago in the solution of boundary layer problems where al aircraft at 60 knots or more. The present invention over ternatively suction or pressure of air at the upper surface 50 comes this latter objection in that the rotor blades in ro of the wing was employed to prevent separation of the tating develop this great lift while the rotor craft re streamlines and so delay the stall condition brought about mains in situ until the necessary amount of VTOL lift is by the use of a too high angle of attack, approximately generated. It is recognized of course that very large 20 degrees. This principle was later applied experiment amounts of power are required to accomplish this end ally to the Fowler and similar flaps which in practice are 55 result, and this could be provided economically if all or set at a very high angle to slow the landing speed while even the major portion of the energy of the power units increasing the lift. Good results were obtained increas used for the propulsion of the aircraft could alternatively ing the Fowler flap C max. 3.2 by some 50 percent. be diverted to the lifting effort. Unfortunately as in the Later experiments by the National Gas Turbine Establish case of the Rotordyne only about 30 percent of the turbo ment in Britain as reported in "Flight' periodical of Sept. 60 prop energy can be transferred to the compressor to pro 30, 1955, envisaged the use similar to illustration 2.13a duce lift. Since the extra energy needed for the VTOL noted above, of blown compressed air as a jet flap at the operation is only required for a minute or two while the trailing edge of an unflapped fixed wing, the air issuing rotorcraft is gaining height, the present invention hopes horizontally for cruising flight and alternately directed to repair this deficiency by creating a supplementary source vertically downward for low landing speed. The experi 65 of power by centrifuging ambient air within the blades ments were said to reveal that while a tremendous amount and taking over the task of propelling the rotor, leaving to of compressed air was required, a C max, of 10 and 12 the compressor the sole task of providing the necessary could be obtained thereby (very likely by fuel-fired compressed air for expulsion from the spanwise slits to means). However it was revealed in 1961 as per illus create the lifting effort required. tration 2.13b previously mentioned that the National Gas 70 In order to provide for the problem of transition from Turbine Establishment had modified its previous recom vertical to translational (forward) flight I provide an mendations and that the single slit should now be a triune auxiliary jet of the by-pass type mounted upon the affair and relocated, the net effect of which would be to fuselage in line with the base of the pylon. It should compel the slipstream over the upper surface to curve have sufficient power to fly the aircraft alone at a speed down and under the wing trailing edge to meet the on 75 of about 70 knots which would be well above the stalling 3,215,366 5 6 point. I prefer the turbo-meca type having a compressor of propelling the rotor is performed by the centrifuging unit in the forward position where it could feed additional and heating of the ambient air mass which it must be air if needed to the pylon and alternatively provide enough noted is an added source of power obtained at a small forward thrust to underwrite the turbo-prop engines when total expense in fuel. the compressor is shut down for transition to forward 5 Of all the forms of civil VTOL aircraft studied the flight. configuration herein outlined would seem to provide the At the commencement of the VTOL operation of this best answer so far for low cost civil city-center hauling rotorcraft the vent on the top camber of the rotor is able to operate within the prescribed limitations of the opened for the admission of air. The propellers of the code of the Civil Aeronautics Board. turbo-prop engines are then put into Zero pitch and the O I do not wish to limit myself to the construction speci engines started. The compressor is activated and com fication described, since experiment may suggest modifica pressed air is bled via the hollow braces to the pylon, tion within the principles stated and I further do not rule thence to the ducted rear portion of the rotor blades to out the introduction of a fuel combustion unit within the start the blades rotating, and later diverted to the span pylon if some benefit should ultimately be realizable by a wise slits to create lift. Substantial increase in temperature of the cold compressed By the time the rotorcraft is airborne and climbing, and air at that point. cruising height attained, transition to forward flight will An object of the invention is to provide a civil airliner require the starting of the auxiliary engine, mainly as a in which all the hazards attendant upon high speed take fail-safe measure, and at the same time putting the pro off and landing are eliminated. peller blades of the turbo-prop into fine pitch, and when 20 An additional object is to provide a civil airliner having the rotorcraft has exceeded the stalling speed, closing off Vertical-take-off and landing characteristics combined with the vent on top of the rotor and declutching the com loW operating cost per passenger-mile. pressor. The air being cut off, the blades will cease to A further object is to provide an airliner having VTOL rotate and can be locked in the transverse position over characteristics to meet city-center to city-center Civil the fixed wings. The auxiliary engine may or may not 25 Aeronautics Board specifications in the short and medium be shut down depending on circumstances. In landing, haul range. the sequence of these operations will be reversed. An additional object is to provide an airliner capable Inherent in the scheme of this invention is the recogni of operating in both VTOL and short-take-off-and-landing tion within the formula for centrifugal force of the ad regimes. vantage obtained under the revolutions square law on and A further object is to provide by the centrifuging of an its application to the jet tip propulsion of this invention ambient air mass entrained within the blades, an extra sup enabling the rotor diameter to be considerably reduced ply of power to meet the heavy demands of short dura and increasing its strength relatively. tion required for VTOL operation, said power addition propulsion increases its efficiency with increased limited only by the amount of fuel that can be consumed. speed. However above 80 percent of sonic velocity say &3 5 An additional object is to provide a military VTOL 900 ft. per second at the periphery would appear to be aircraft capable of carrying relatively large payloads at the upper limit for civil operation. 450 knots cruising speed. With this upper limit in mind it will be seen that a rotor Another object is to provide a VTOL aircraft having tip 30 feet in diameter would be rotating at twice the r.p.m. jet propulsion possessing a low noise factor by reason of of a rotor 60 feet in diameter, so that one pound of air 40 increased volume but lower velocity within the jet. at the periphery of the smaller rotor would under these A further object is to provide a rotorcraft in which all circumstances possess twice the centrifugal force of the the fuel is completely gasified before being exhausted from larger rotor under the formula for centrifugal force the rotor. A further object is to provide a lift component on both WRN2 advancing and retreating blades by the built-in elevation 2.933 of the plane of rotor rotation relative to the line of flight where W is the weight in pounds, R the radius in feet, and during autorotation. Nthe revolutions per minute. An additional object is to provide a rotor-craft of such This is important since some degree of compression by robust rotor construction as to withstand the high transla centrifugence is required within the fuel-air mixture for tional velocities with a minimum of vibrational stress. proper combustion, and while the centrifuging of the am FIGURE 1 is a plan view of the first embodiment of bient air mass does not compare with the effectiveness of the rotorcraft. the air compressed by the compressor this deficiency is FIGURE 2 is a side view of the first embodiment of the somewhat remedied by the large volume of the ambient rotorcraft. air available and the very great possibility that the noise 5 5 FIGURE 3 is a front view of the first embodiment of factor so prevalent with the Fairy “Rotordyne' will be the rotorcraft. reduced to acceptable levels. FGURE 4 is a sectional side view of the pylon con Other considerations having a pertinent bearing on the struction. matter are that the deflection of a centilever under load FIGURE 5 is a sectional plan view of the rotor blade tip increases as the cube of the span, consequently from an 60 showing location of combustion units and spanwise slits. engineering standpoint the smaller rotor would be rela FIGURE 6 is a cross-sectional view of the blade profile tively 8 times stronger so necessary since operating under of the two-bladed rotor of the first embodiment. a C max. 7.5 at least as against 1.4 with the Rotordyne FIGURE 7 is a cross-sectional view of the blade pro 1rotor, the smaller rotor will have to carry 5.4 times the file of the multi-blade rotor of the second embodiment. load per square foot of blade surface. In the drawings FIGURES 1, 2, and 3, showing the One clear-cut advantage to be gained by the present in first embodiment, the rotor comprises a pair of rigid hol vention is that with the Fairy “Rotordyne' all the highly low blades 1 rotatable upon anti-friction bearings 2 se compressed air energy available to the rotor was directed cured to a pylon 3 superimposed on a fuselage to which to the propulsion of the rotor blades, generating the nec is secured landing gear 5 fixed wings 6 having front and essary lift force by conventional aerodynamical means, rear hinged flaps 7 and aerodynamic surfaces 8 for the while with present proposals the whole of this available directional control of the aircraft. Cold compressed air energy is directed to the production of lift by the jet flap generated by the gas turbine compressor assembly 9 se principle the effectiveness of which requires velocities ap cured to the fixed wings 6 is conveyed via the streamlined proaching the speed of sound in the jet sheet, and this hollow braces 10 and duct 24 within the pylon 3 and cy can only be attained with high air compression. The task 75 lindrical ducts within the rear portion of the rotor

3,215,366 10 8. Improvements in sustaining rotors for at cruising speed more than 85 percent of the load, a rotor of the rotordyne configuration, comprising a rigid hollow assembly sustaining the balance of the load at said cruis rotor blade, mounted on a pylon superimposed on a fuse ing speed and sustaining the whole of the load in the lage and having valved means for the admission of VTOL regime, said rotor assembly comprising a plurality ambient air into the upper central portion of said rigid of rigid hollow non-articulated blades having longitudinal hollow rotor blade, rotor propulsion jet orifices at the tip ducts in the rear portion of said blades through which air of said rotor blade, fuel combustion units and a fuel is conveyed and ejected to provide in ordered sequence tip source centrifugally activated disposed midway of said jet propulsion and airborne support by the jet flap prin ambient air opening and said tip jet orifices, a series of ciple, said longitudinal ducts in the rear portion of said longitudinal cylindrical fluid pressure ducts located in the blades being cylindrical to sustain interior fluid pressure rear portion of said rigid hollow rotor blade linking said 10 and having spanwise slits open to the atmosphere in which tip jet orifices with a source of compressed air via said cold compressed air is conveyed and ejected at the tip to pylon, spanwise slots in said longitudinal cylindrical fluid provide initially rotor propulsion, in turn centrifuging pressure ducts downwardly exhausting said compressed ambient air admitted into and entrained via the front air into the atmosphere to create jet flaps, a valve cen 5 portion of said blades, said centrifuged ambient air being trifugally activated in said cylindrical ducts closing off heated and ejected at the blade tip to provide constant the Supply of said compressed air to said tip jet orifice, rotor propulsion, said cold compressed air in ordered se a fuel combustion unit located midway between said cen quence by valve means centrifugally activated being di trifugally activated valve and said tip jet orifice, and verted from said blade tip to said spanwise slits generat ignition means associated with all said combustion units. 20 ing lift by means of an air jet flap at the desired rotor 9. Improvements in sustaining rotors for convertiplanes rotational speed. of the rotordyne configuration comprising a non-articu 11. In a rotorcraft of the Fairy “Rotordyne' configura lated rotor of rigid hollow construction mounted upon tion of the type described in claim 1, the diameter of said a pylon Superimposed on a fuselage, said rigid hollow rigid hollow non-articulated blades of said rotor assembly rotor being divided into a front and a rear portion, said 25 having a maximum dimensional limit, said maximum limi rotor having a series of one-way rotation-inducing jet tation being determined by a capability of generating, by orifices at the tip, a valved opening in the upper central centrifugal force, a minimal degree of compression within portion of said rotor for the admission of ambient air, said Said ambient air sufficient to create, when fuel is added front portion of said rotor having a series of longitudinal and ignited, an explosive ram force within the gas mix ducts linking said ambient air valved opening with said 30 ture, said maximum blade dimension bearing an inter tip jet orifices, fuel combustion units disposed within said dependent relationship imposed by the limitation of sonic longitudinal ducts, a fuel source within said front portion speed at the blade tip. of Said rotor communicating with said fuel combustion units, said fuel source being activated by centrifugal References Cited by the Examiner means, the rear portion of said rotor containing longi 35 tudinal cylindrical fluid pressure ducts, said fluid pressure UNITED STATES PATENTS ducts being valved centrifugally and terminating in one 2,511,025 6/50 Tucker et al. ------244-7 of said tip jet orifices, a fuel combustion unit located be 2,585,676 2/52 Poisson-Quinton ----- 244-42.4 tween said centrifugally activated valve and said tip jet 2,653,778 9/53 Bennett et al. ------244-5 orifices and communicating with said fuel source, said 40 2,925, 129 , 2/60 Yuan et al. ------170-135.4 cylindrical fluid pressure ducts communicating via said 2,989,268 6/61 Andrews ------244-7 pylon with a source of compressed air, said fluid pressure 3,096,041 7/63 Cheeseman et al. ------244-7 ducts having spanwise slots opening to the atmosphere such 3,139,936 7/64 Davidson et al. ------170-135.4 that compressed air exhausted therefrom will create a jet FOREIGN PATENTS flap, accelerate the boundary layer and simultaneously 45 create a vertically downward diversion of the rotor slip 735,106 8/55 Great Britain. Stream. 10. In a rotorcraft of the Fairy “Rotordyne” configura FERGUSS. MIDDLETON, Primary Examiner, tion having VTOL characteristics, a fixed wing sustaining MILTON BUCHLER, Examiner,