Abstract: A constant-speed twin spool turboprop unit including a twin spool gas generator having a low-pressure spool and a high-pressure spool each including a compressor and a turbine which drives the compressor, is described in which at least one propeller of the unit is driven by at least the high-pressure spool of the gas generator.

Abstract: An improved hydraulic system for a twin propeller marine propulsion unit. A vertical drive shaft is operably connected to the engine of the propulsion unit and carries a pinion that drives a pair of coaxial bevel gears. An inner propeller shaft and an outer propeller shaft are mounted concentrically in the lower torpedo section of the gear case and each propeller shaft carries a propeller. To provide forward movement for the watercraft, a sliding clutch is moved in one direction to operably connect the first of the bevel gears with the inner propeller shaft to drive the rear propeller. A hydraulically operated multi-disc clutch is actuated when engine speed reaches a pre-selected elevated value to operably connect the second of the bevel gears to the outer propeller shaft, to thereby drive the second propeller in the opposite direction.

Abstract: A device for creating a localized water jet within a body of water allows for the displacement of material from the floor of the body of water. The device includes two powered screws within a jet pipe. The screws are arranged coaxially and their direction of rotation, pitch, and speed of rotation are arranged such that the torque produced by one of the screws tends to counteract the torque produced by the other, allowing for improved control of the device.

Abstract: A gear-based airboat transmission is provided for driving a pair of coaxial, counter-rotating propellers. The transmission includes a fore output gear rotatably affixable within a housing and affixable to the inner shaft for rotating the outer propeller. An aft output gear is rotatably affixable within the housing and is affixable to the outer shaft coaxial with the inner shaft for rotating the inner propeller opposite the outer. The aft output gear is generally coaxial with the fore output gear. An intermediate gear shaft has a fore end and an aft end, and both ends are opposedly and rotatably affixable within the housing. This bracing confers additional stability to the transmission, conferring longer life and decreased vibration. An intermediate gear is mounted thereon, and is positioned in driving relation to the fore output gear. A drive gear is rotatably affixable within the housing and is affixed for corotation with a drive shaft.

Abstract: A twin engine, coaxial, dual-propeller propulsion system employing a unique transmission having two independent drive trains. The first of the two engines exclusively drives a first drive train, which in turn rotates a forward multi-bladed propeller assembly. The second engine exclusively drives a second drive train, which in turn rotates an aft multi-bladed propeller assembly. Thus, the propellers of this propulsion system, even though coaxial, are driven by separate engines. The propulsion system also enjoys the increased propulsive efficiency of a coaxial dual-propeller design as the first drive train rotates the forward propeller assembly in a first rotational direction and the second drive train rotates the aft propeller assembly in the opposite direction. Further, the propulsion system employs pitch change control mechanisms which independently control the respective pitch of the blades of the two propeller assemblies.

Abstract: A marine propulsion system with counter-rotating propellers is provided with the capability of causing the propellers to rotate at different speeds. A first gear is attached to an inner propeller shaft and a second gear is attached to an outer propeller shaft. The inner and outer propeller shafts are arranged in coaxial and concentric relation for rotation about an axis of rotation. A driveshaft is connected to a pinion gear which engages the teeth of the fore and aft gears at different effective diameters. The pinion gear meshes with a first plurality of gear teeth on a beveled surface of the fore gear while a second set of gear teeth of the pinion gear mesh with a second plurality of gear teeth on a beveled surface of the aft gear. Because of the different effective diameters of the first and second pluralities of gear teeth, the inner and outer shafts rotate at different speeds.

Abstract: A shifting mechanism for an outboard drive of a watercraft provides reduced coupling shock when the forward gears are engaged by a dual clutch assembly, as well as provides for consistent and quick engagement of the clutch assembly with the gear. The shifting mechanism involves a first gear and a corresponding first clutch, and a second gear and a corresponding second clutch. A plunger carries the first and second clutches which are arranged on the plunger at unequal distances from their respective gears. This nonuniform spacial relationship between the clutches and gears causes one clutch to engage its corresponding gear before the other clutch engages its corresponding gear. The staggered engagement decreases shock on the transmission and permits quicker engagement between the clutches and gears.

Abstract: A split fan for providing lift for an aircraft is described. In one embodiment, a main engine shaft extends to the split fan, and a portion of the split fan is located at an elevation above the main engine shaft and a portion of the split fan is located at an elevation below the main engine shaft. In the one embodiment, the split fan includes an outer casing configured to be mounted to a fuselage of the aircraft, a first stage rotor including a shaft, a gear secured to the shaft, and a plurality of rotor blades radially extending from the shaft. The split fan also includes a second stage rotor including a shaft, a gear secured to the shaft, and a plurality of blades radially extending from the shaft. A drive shaft having a first end and a second end is coupled at the drive shaft first end to the main engine shaft.

Abstract: A helicopter having two engines driving a single rotating drive shaft on which are mounted two spaced counter-rotating coaxial rotors at the same speed and having a tail boom free of a tail rotor and supporting two horizontally spaced pairs of air foils for controlling the direction of yaw in flight.

Abstract: An aircraft has at least one drive motor coupled to first and second propellers for forward thrust of the aircraft. The first propeller is dimensioned for takeoff and landing conditions and for flight conditions below a predetermined first flight altitude. The second propeller has a radius which is larger than a radius of the first propeller and is dimensioned for a second flight altitude which is substantially greater than the first flight altitude. The two propellers are alternatingly coupled with the at least one drive motor so that the two propellers are respectively individually adapted to the power of the at least one drive motor for a full utilization of the power of the at least one drive motor for forward thrust.

Abstract: A transmission for a counter-rotational propeller system of a watercraft outboard drive provides an increased flow area for exhaust discharge behind the transmission within the lower unit. The transmission includes a pair of counter-rotating gears. A front clutch selectively drives an inner propulsion shaft by engaging the front gear. A rear clutch selectively drive an outer propulsion shaft by engaging either of the gears. The front clutch lies forward of the front gear and the rear clutch is interposed between the gears. The clutching mechanism thus entirely lies forward of the rear gear to provide more space for exhaust discharge flow behind the transmission.

Abstract: A simple structured propeller shaft assembly for a counter-rotating propeller system of a watercraft outboard drive prevents fishing line, weeds and like debris from entangling on a shaft of the propeller system and damaging the lubricant seals of the shaft assembly. The shaft assembly includes a nut which threads partially onto an end of an outer propeller shaft of the propeller shaft assembly. A thrust washer, carrier by an inner propeller shaft, includes a front hub which partially inserts into the nut adjacent to the end of the outer shaft. The nut, thrust washer and outer shaft end together define a labyrinth path into the space occupied by the lubricant seals between the inner and outer shafts. This labyrinth path inhibits weeds and like debris from wrapping around the inner shaft at a point adjacent to the lubricant seals.

Abstract: An improved transmission bearing assembly for a counter-rotating propeller system of a marine outboard drive directly journals the driven gears of the transmission on the propulsion shafts of the outboard drive. The hub of one driven gear is journaled between a portion of an inner propulsion shaft and a hollow end of the outer propulsion shaft. The bearing assembly also supports the hollow end of the outer propulsion shaft at a front end of a bearing carrier and supports a rearward section of the outer shaft at a rear end of the bearing carrier. The span between the bearing assemblies journaling the outer propulsion shaft within the bearing carrier is increased by positioning the bearing assemblies at the ends of the bearing carrier. The positions of the bearing assemblies at the ends of the bearing carrier thus improves the stability of the outer propulsion shaft.

Abstract: A transmission for a counter-rotating propeller system of a watercraft outboard drive includes a reduced friction coupling between the inner and outer shafts which permits transfer of the thrust loading on the inner shaft to the outer shaft under a reverse drive condition. The inner and outer shafts include opposing transverse surfaces which are separated by a pair of anti-friction washers. The washers allow the shafts to rotate in opposite directions with minimum friction, while allowing the opposing surfaces to act on each other through the washers to transfer the trust loading when the watercraft is driven in reverse.

Abstract: A shifting mechanism for an outboard drive of a watercraft provides reduced coupling shock when the forward gears are engaged by a dual clutch assembly, as well as provides for consistent and quick engagement of the clutch assembly with the gear. The shifting mechanism involves a first gear and a corresponding first clutch, and a second gear and a corresponding second clutch. A plunger carries the first and second clutches which are arranged on the plunger at unequal distances from their respective gears. This nonuniform spacial relationship between the clutches and gears causes one clutch to engage its corresponding gear before the other clutch engages its corresponding gear. The staggered engagement decreases shock on the transmission and permits quicker engagement between the clutches and gears.

Abstract: Transmission for a single engine drive for dual concentric propellers in a straight or V-drive arrangement with the straight-drive including four shafts and nine gears and the V-drive adding two more shafts and four more gears.

Abstract: A variable-pitch propeller or fan comprises a hollow boss, a number of propeller blades fitted rotatably on the boss, and also an adjusting element which is axially slidable in the boss and has a number of grooves running essentially at right angles to the direction of sliding, each propeller or fan blade having a control pin which is placed eccentrically relative to its rotary shaft and is slidingly accommodated in a groove of the adjusting element. In order to increase the range of adjustment each groove comprises an essentially straight part and also a second part connecting to the straight part and forming an angle with the essentially straight part.

Abstract: A shifting mechanism for an outboard drive of a watercraft provides reduced coupling shock when the forward gears are engaged by a dual clutch assembly, as well as provides for consistent and quick engagement of the clutch assembly with the gear. The shifting mechanism involves a first gear and a corresponding first clutch, and a second gear and a corresponding second clutch. A plunger carries the first and second clutches which are arranged on the plunger at unequal distances from their respective gears. This nonuniform spacial relationship between the clutches and gears causes one clutch to engage its corresponding gear before the other clutch engages its corresponding gear. The staggered engagement decreases shock on the transmission and permits quicker engagement between the clutches and gears.

Abstract: A ship's drive with two counterturning propellers, the rear propeller of which is fastened to an inner shaft and the front propeller of which is fastened to the head end of a hollow shaft, which runs concentrically with the inner shaft. The hollow shaft is connected to a gearing and the inner shaft is connected to a propulsion unit. A gearwheel is disposed at the foot end of the hollow shaft which engages a further gearwheel which is fastened to an input shaft running parallel to the inner shaft. The input shaft can be connected with the output of a second engine.

Abstract: A marine drive (10) has a spool (36) positioned in the lower horizonal bore (28) and supporting a dual propeller shaft assembly (38, 40). An exhaust passage (130) includes a passage (132) in the drive housing (26) communicating with the horizontal bore (28) at the spool (36), and a spool exhaust passage (134) passing exhaust rearwardly through the spool to the propeller through-hub exhaust passages (136, 138), providing through-hub exhaust through dual propellers (12, 14). An oil passage (152) in the housing (26) communicates with the horizontal bore (28) forwardly of the exhaust passage (132) and lubricates the dual propeller shaft assembly.

Abstract: The invention concerns the mounting of propeller blades to a ring-shaped rotor. The blades are of the variable pitch type, and the shank of each blade extends through a respective hole in the rotor. Each hole contains an annular shelf which is fastened to the wall of the hole and surrounds each shank. Each shank bears a pair of bearing races which sandwich the annular shelf in order to connect the blade to the rotor. Bearing rollers are positioned between the annular shelf and the bearing races.

Abstract: A marine drive (10) has two counter-rotating surface operating propellers (12, 14). Inner and outer concentric counter-rotating propeller shafts (40, 42) are supported by a spool assembly (38) locked and retained against rotation and against axial movement in the lower horizontal bore (28) in the torpedo (34) of the drive housing (26) by axially spaced left and right hand threads (44 and 46). A thrust bearing assembly (98) transfers thrust from the outer propeller shaft to the inner propeller shaft during rotation of the propeller shafts in opposite axial direction and is axially located between fore and aft driven gears (76 and 78). Propeller shaft sealing and bearing structure, and propeller self-centering mounting structure is provided.

Abstract: A system for changing pitch in aircraft propfans is disclosed, in which a motor, located at a stationary position, changes pitch of the blades by of a gear train. Three features of the system are that a feather brake can override the motor and drive the blades toward feather; a unison brake can prevent pitch from undergoing excursions toward fine pitch when propeller speed exceeds a limit; and the motor is non-rotating in the absence of pitch change. A pair of such systems can be used in a counterrotating propfan system, in order to independently change pitch of the propfans.

Abstract: A lift generating method and apparatus for aircraft is provided which generates lift in forward flight, in vertical flight or while hovering. A disk (24) is positioned between first and second counterrotating blade assemblies (22 and 36). The disk (24) generates lift in vertical flight or while hovering due to radial flow of air over an upper surface (28) thereof. In forward flight, the disk (24) functions as a fixed wing to generate lift. The assemblies (22 and 36) may be rotated to provide equal and opposite torques so that a torque compensating tail rotor is unnecessary.

Abstract: A strut mounted, counter rotation marine propeller propulsion system of the single engine is provided including a depending propeller shaft strut from which aligned front and rear propeller shafts are supported including remote ends disposed exteriorly of the strut and having front and rear propellers, respectively, mounted thereon and adjacent ends drivingly interconnected through the utilization of bevel gearing within a journal hub carried by the lower end of the strut. The forward extremity of the front propeller shaft is removably coupled to the rear end of a rearwardly and downwardly inclined power shaft journaled through the bottom of the associated hull and the strut includes horizontally outwardly projecting and forwardly and upwardly inclined opposite side water deflector plates for smoothing out the water discharge, in conjunction with the strut itself, from the front propeller.

Abstract: A drive train assembly for a rotor assembly having ducted, coaxial counter-rotating rotors includes a sprag clutch, an engine coupling subassembly, a transmission coupling subassembly, and a drive shaft mechanically interconnected at the ends thereof to the engine and transmission coupling subassemblies, respectively. The drive train assembly is design optimized to maximize the functional capability of the sprag clutch, the engine coupling subassembly including an external crown spline coupling, internal spline coupling combination that is mounted in combination with the sprag clutch so that loads transmitted through the external crown spline coupling react through the center of the sprag clutch.

Abstract: In one type of aircraft propulsion system, propeller blades are mounted on a ring which surrounds a turbine. An annular space exists between the turbine and the ring. If a propeller blade should break free, the unbalanced centrifugal load tends to deform the ring. The invention reduces the deformation, as by locating spacers between the turbine and the ring.

Abstract: The invention concerns a system for controlling an aircraft propeller. A hydraulic motor controls pitch of the propeller blades. The propeller blades are characterized by the absence of feather-inducing counterweights. An overspeed governor senses when propeller speed exceeds a limit, and, in response, assumes control of the hydraulic motor and drives the blades toward a coarsened pitch position, which reduces the propeller speed. In another form of the invention, a mechanical brake can override the hydraulic motor and mechanically retard a rotating gear, which causes the propeller blades to move toward a coarsened pitch.

Abstract: The invention concerns reduction of tip vortices in aircraft propellers, wherein a fence having anhedral or dihedral is attached to the blades of the propeller. Another form of the invention is applicable to counterrotating propeller systems, wherein a fence is attached to the blades of the forward propeller of the system, and no fences are attached to the aft propeller.

Abstract: A contrarotating propeller type propulsion system having first and second output rotary cylinders which are carried individually on an outside support cylinder fixedly secured to a first support structure, the first output rotary cylinder being borne on the outer peripheral surface of the first support cylinder through bearings and the second output rotary cylinder borne on the inner peripheral surface of the first support cylinder through bearings. The first and second output rotary cylinders serve to support the first and second contrarotating propellers, respectively. The first and second output rotary cylinders are supported on the first support cylinder at two axially spaced points. The driving shaft is borne on a second support cylinder fixedly secured to the support structure and surrounded by the first support cylinder.

Abstract: The invention concerns a pitch change mechanism for an aircraft propeller in which a common ring gear (51) changes pitch of all propeller blades on a given rotor simultaneously. Motion of the ring gear (51) is induced by a planet (40)-and-carrier (101) system driven by a pinion (110). Acceleration of the pinion causes a change toward flat pitch. Deceleration of the pinion causes change toward feathered pitch. If the motor driving the pinion fails, a large deceleration occurs, driving the blades to a safe, feathered position.

Abstract: The invention concerns pitch-change mechanisms, of the planetary gear type, for use in aircraft propellers. Planet gears engage three ring gears at different gear ratios, thereby causing relative rotation of the ring gears to occur when the planet gears rotate. A linkage between the ring gears and the propeller blades converts the relative rotation into a change in pitch. A sun gear drives the planet gears. A planet carrier prevents excessive skew of the planets from occurring if one of the ring gears should break, and thereby release its load on the planet gear.

Abstract: The invention relates to pitch-change systems for aircraft propfans of the counterrotating type. The pitch of each propfan stage is independently adjustable. Further, in the case where one of the propfan stages acts as a rotating obstacle for a mechanism which causes pitch change of the other stage, a system is provided which transfers the pitch-change torque through this obstacle-stage without being affected by the speed of the obstacle-stage.

Abstract: The invention concerns aircraft propellers of the variable pitch type. Each propeller blade is carried by a trunnion which is rotatably mounted to a common ring. Each trunnion contains a reduction gear set which is driven by a radial shaft. The reduction gear sets multiply the torque applied by the shafts, thus allowing shafts of reduced diameter to be used. The reduced diameter is important when the shafts must pass through a turbine flowpath, and thus be concealed within turbine blades. The reduced diameter shafts can be easily concealed within turbine blades without redesigning and compromising blade aerodynamics.

Abstract: The invention relates to pitch-change systems in aircraft propellers. The invention includes redundant planetary gear systems, each of which can independently change pitch if the other fails. The invention also includes a system for reducing displacement of the planets, which can occur during a failure.

Abstract: A propfan engine having two oppositely rotating fan rotors both driven by a low-pressure turbine by way of a drive shaft includes a reversing transmission. The reversing transmission drives one fan rotor, while the other fan rotor is coupled directly to the drive shaft. This construction permits a favorable design of the rotational speeds of the fan rotors and of the turbine and, in comparison to a conventional transmission, requires less space and weight for both fan rotors.

Abstract: The invention concerns a cowling for aircraft propulsion systems of the counterrotating propeller type. The cowling includes a pair of mounting rings located fore and aft of a propeller array. Removable panels extend between the mounting rings and contain openings through which the propeller blades extend.

Abstract: A variable pitch propeller module includes first and second multi-bladed propellers arranged to be driven in opposite rotational directions by a reduction gear mechanism, via shafts. First and second drums are rotatably mounted on the hubs of the first and second propellers and the drums are arranged to rotate the blades of the propellers. A hydraulic motor is mounted coaxially on and rotates with the second propeller, the hydraulic motor being arranged to drive the drums by via a pitch change gear assembly. A hydraulic fluid feed tube extends coaxially through the reduction gear mechanism and both propellers to supply hydraulic fluid to the hydraulic motor. An annular sleeve is positioned coaxially on the tube. The hydraulic fluid feed tube has passages and the sleeve has passages which are aligned to allow hydraulic fluid to flow to the hydraulic motor to vary the pitch of both blades. The feed tube and sleeve are moved axially to control the flow of hydraulic fluid to the hydraulic motor.

Abstract: A new and improved gas turbine engine including a gas generator and a power turbine is disclosed. The power turbine includes a first rotor having a plurality of first turbine blade rows extending radially outwardly therefrom, and a second rotor having a plurality of second turbine blade rows extending radially inwardly therefrom. The power turbine is supported aft of the gas generator and is effective for receiving combustion gases therefrom and expanding the gases through the first and second turbine blade rows for extracting substantially all output power therefrom for driving the first and second rotors in counterrotating directions.

Abstract: A method of creating thrust reversal for an engine having counter-rotating forward and rear propeller blades. The forward blades are set at a positive angle of attack to produce an orderly flow of air toward the rear blades. The rear blades are set at a negative angle of attack to produce reverse thrust. The net effect is that the thrust produced by the rear blades overbalances that of the forward blades to produce net thrust reversal.

Abstract: An arrangement for transferring power of an engine to front and rear propellers of a ship comprises an inner propeller shaft directly coupled to the engine, an outer propeller shaft coupled to the engine via the planetary gear set in a manner such that the front propeller rotates in a direction opposite to the direction the rear propeller rotates. The planetary gear set includes first planetary gears coupled to the inner propeller shaft and secondary planetary gears coupled to the outer propeller shaaft and one clutch is provided between each pair of first and second planetary gears. Since there are provided a plurality of clutches, the torque imposed on each clutch is relatively small. Also, the torque on the clutch is reduced by the planetary gear set. Therefore, a clutch of small capacity can be employed. This makes the arrangement compact and the maintenance of the clutch easy.

Abstract: An arrangement for the adjusting of rotor blades of a propfan turboprop engine equipped with two counter-rotating propfan rotors has a number of double-toothed planet wheels which are fastened in a rotatably disposed web. The web is supported on the side of the housing by planet members disposed on one of the propfan rotors. The two toothings of the planet wheels are in operative connection with ball spindle adjusting rings. Using an adjusting motor, a relative movement of the web can be achieved with respect to the housing, whereby the blades of two counter-rotating rotor blade rings can be swivelled. According to the invention, an adjustment of rotor blades will also be possible when no stationary housing parts are available for the support.

Abstract: A dual boat propeller structure is described for counter-rotation of the propellers. A housing is located outside the boat hull in alignment and connection with an engine shaft. The housing stores a conversion mechanism with which coaxially-mounted propeller shafts are brought into counter-rotation to correspondingly rotate the propellers. A strut interconnects the housing to the boat hull in a manner so as to reduce vibrations from the counter-rotating mechanism. The housing has a frusto-conical shape with which a large diameter aft end is sized commensurate with the hub of the propellers for smooth water flow.

Abstract: High by-pass fan jet engine includes counterrotating turbine blade sets for receiving hot combustion gases from a core engine portion and driving the fan blades through a planetary gear-type reduction gear assembly. Lightweight, highspeed, concentric, counterrotating shafts transmit power from both turbine blade sets to the fan via the reduction gear assembly. A pair of planetary gear assemblies with fixed fing gears and a rotatable common planetary gear carrier is used to drive a single set of fan blades via the carrier, and a pair of planetary gear assemblies with a fixed common planetary gear carrier and rotatable ring gears is used to drive two or more counterrotating fan blade sets via the ring gears. A low pressure "booster" compressor feeding the core engine portion can be directly driven from one of the two high speed shafts.

Abstract: A dual counterrotating propeller drive mechanism for a marine propulsion system incorporates a torque splitting device which consists of a differential gear means and a ratio gear means. The torque splitting device assigns a selectable fixed fraction of the engine torque to each propeller regardless of power, thrust, and speed conditions. The rear one of the two propellers adjusts its rotational speed relative to the front propeller in response to changes in the front propeller's wake and in this way maintains optimum propulsive efficiency over a wide range of operating conditions. Furthermore, precise matching of front and rear propeller parameters for a given application is no longer required.

Abstract: A gas turbine engine having a core for generating combustion gases, a power turbine, an unducted fan section and a booster compressor. The power turbine includes two counterrotating turbine blade rows which are interdigitized and serve to rotate counterrotating first and second drive shafts, respectively. The unducted fan section also includes counterrotating spaced apart variable pitch fan blade rows which are respectively connected to the first and second drive shafts. A booster compressor is axially positioned between the spaced apart fan blade rows. The booster compressor likewise includes first and second blade rows which are counterrotating and interdigitated and are likewise driven by the first and second drive shafts. The engine is supported by two stationary support frames to permit the nacelle to be nonstructural. The core engine is a modular unit so that it can be separable from the rest of the engine.

Abstract: A high bypass ratio turbofan engine having a fan section, a booster compressor disposed aft of the fan section relative to the flow of combustion gases through the engine, and a core section disposed aft of the booster compressor. A low pressure counterrotating turbine, disposed aft of the core section, is used for driving the fan section and the booster compressor. The counterrotating turbine includes at least one set of rotating turbine blades and at least one set of oppositely rotating counterrotating turbine blades. A twin spool shaft is provided for coupling the turbine blades to the booster compressor and for coupling the counterrotating turbine blades to the fan section. A reduction gear is disposed in the drive shaft for coupling the turbine blades to the fan section and for reducing the rotational speed of the turbine output power to match the rotational speed of the fan section thereby splitting the usable work of the turbine blades between the fan section and the booster.

Abstract: A marine contra-rotating propeller system comprises a large gear driven by an engine, and a plurality of small gears disposed so as to respectively mesh with the large gear at a plurality of fixed positions along the circumference of the large gear. Planet gears are respectively mounted to the gear shafts of the small gears. A sun gear and an inner-toothed gear are respectively meshed with the planet gears. A rear propeller is mounted to an inner shaft serving as a gear shaft of the sun gear. A front propeller is mounted to a tubular outer shaft serving as a gear shaft of the inner-toothed gear. The present invention can eliminate, with the simple construction, the inconvenience caused by a differential planetary gear operations in the prior art, can derive a propeller efficiency to the maximum extent.

Abstract: A coupling arrangement for supporting a power turbine in a gas turbine engine. The power turbine section comprises a stator structure, first and second rotors, and first and second bearings. The first and second rotors are coaxially disposed about a longitudinal axis of the stator. An annular gas flowpath is coaxially positioned between the first and second rotors. Annular arrays of turbine blades are coupled to the first and second rotors and extend into the flowpath so that a gas stream flowing through the flowpath reacts with the turbine blades causing the rotors to counterrotate. The first bearings are interposed between the first rotor and the stator structure to rotatably secure the first rotor to the stator structure. The second bearings are interposed between the second rotor and the first rotor to rotatably secure the second rotor to the first rotor.

Abstract: The invention relates to a boat propeller unit with double, counter-rotating propellers. The forward propeller is designed to function without cavitation, while the after-propeller is optimally cavitating by being made cupped and with a blade width of between 60% and 75% of the blade width of the forward propeller.