Abstract: A marine propeller (100) combines progressive pitch with both increasing pitch and increasing progressiveness of pitch along at least a portion of increasing radii from the axis of rotation to the outer blade tip. A five blade propeller is provided which accommodates thermal warpage of the outer blade tips, such that the same propeller includes two different types of blades, one blade having increasing pitch with increasing radii all the way to the outer blade tip, and the other type of blade having increasing pitch to a given radius and then decreasing pitch with increasing radii to the outer blade tip. The latter blade type is preferred and has a hump in the pressure surface at the noted given radius between portions of increasing and decreasing pitch with increasing radii.

Abstract: A propeller type runner is described in which the leading edge of each blade "leans" forward from the root in the direction of rotation to reduce cavitation and increase efficiency. The "lean" provided to each blade of a five blade design is such that the leading edge of each blade obscures a large portion of the trailing edge of the preceding blade.

Abstract: An axial flow fan has each of its fan blades provided with an integrally formed centrifugal element which extends substantially parallel to an imaginary plane containing a central axis of the fan. Some of the air flow passing through the fan collides against the centrifugal elements, which deflect the air in the radial directions. A disk-like air barrier is thus formed around the fan blades, whereby a countercurrent flow and circulation flow are eliminated. The fan efficiency is also improved.

Abstract: A water pump is comprised of a housing having therein a pumping portion and a bearing portion, a shaft rotatbly supported by the bearing portion, an impeller fixedly mounted on one end of the shaft and having a frontward side and a rearward side, a plurality of equally pitched vanes in the circumferential direction, and a hole device penetrating the impeller with making an angle relative to the rotation direction thereof.

Abstract: A blade device for turbo-engines, comprising a blade shell, a blade core and a blade base, has a blade core comprising a bundle of small tubes which provides the blade device with high stability and stiffness. The arrangement has the advantage that the blade device can be used universally in the case of almost all blade devices, and the blade core permits a heat exchanger function.

Abstract: Disclosed is a system and method for suppressing rotor noise by distributing mass and momentum sources and sinks on the rotor blade. A source is located on the blade, and therefore has the directivity of moving, as opposed to a stationary source. Moreover, the motion of the blade with respect to the observer amplifies the sound from the source in a manner similar to the manner in which motion of the blade amplifies all other sources of noise associated with the rotating blade. Two sources can be used to cancel noise. The first source, created by ejecting air from or drawing air into the blade, is used to cancel the "load" portion of rotor noise. The second source, created by developing a radial force with a proplet, is used to cancel the "thickness" portion of rotor noise. More control can be achieved by time modulating the rate of suction or the amplitude of radial force developed by said proplet.

Abstract: A beta phase nickel aluminide microalloyed with iron having improved ductility. Nickel aluminide intermetallics alloyed with no more than about 0.5 atomic percent iron have significantly improved room temperature ductility over conventional unalloyed beta phase nickel aluminides or beta phase nickel aluminides alloyed with higher percentages of iron.

Abstract: An air conditioning system having a fan that moves air over the outside heat exchanger of the system. The fan is of the bladed axial flow type. A winglet projects curvilinearly both radially outward from the trailing end of the tip of each blade of the fan and perpendicularly upward from the blade pressure surface. A conduit directs condensate formed on and dripping from the system inside heat exchanger to a collector located under the fan. The blade winglets scoop condensate from the collector and draw the water inward toward the center of rotation of the fan, where air moving through the fan slings the water on to the outside heat exchanger.

Abstract: Improved mixing performance with reduced power input is obtained in an agitated oxidation reactor for converting an aromatic alkyl to the corresponding aromatic carboxylic acid by decreasing the clearance between the lowermost impeller element and the reactor bottom and by providing a flat blade turbine as the upper impeller element.

Abstract: An aircraft propeller blade utilized in subsonic flight at relatively slow turning applications with relatively high power coefficients. The blade in plan form is tapered at both ends with the maximum chord approximate the 44% percent station of the blade, the leading edge of the blade being swept behind the longitudinal axis of the blade near its tip and the trailing edge is convex and essentially straight from its maximum chord outward to the tip.

Abstract: An air grain conveyor comprising a means for generating high velocity air, a grain ejection section, a connection between said means and said ejector section whereby the high velocity air is ejected into the ejection section, and a grain hopper attached to the ejector section whereby grain is drawn into the ejector section and conveyed to a discharge section wherein the velocity of air borne grain is slowed prior to deposit of the grain into a receiver.

Abstract: An asymmetric set of pre-swirl vanes (stators) and a specially matched propeller for use on an inclined shaft. The propeller is designed by considering the mutual interaction of the propeller on the vanes and the vanes on the propeller. The propulsor unit provides the following:1. increased propulsion efficiency due to the reduced rotational (swirl) and axial kinetic energy losses in the propulsor's slipstream;2. reduction or elimination of propeller cavitation;3. reduction or elimination of unsteady propulsor forces as well as propulsor-induced hull vibrations.A unique feature of the present invention is that a prior art flat faced commercially available propeller can be modified to match the vane flow field for optimum propulsor performance. The use of commercially available propellers reduces the installation or hardware cost significantly and allows the propeller to be repaired easily if damaged.

Abstract: Thermally actuated flow diverters for gas turbine engines are provided which include an arrangement of vanes in spaced overlapping array, which direct, e.g. coolant air flow to rotating engine components, each vane having 3 foil components joined at 3 hinge points. That is, a leading foil positioned on the suction side of the vane, a trailing foil pivotably mounted to a rearward portion of such leading foil at a first pivot axis and a third foil positioned on the pressure side of the vane connecting a forward portion of such leading foil and such trailing foil at second and third pivot axes respectively. Either the third foil or the leading foil is fixedly mounted to engine walls of the same material, the other of these two foils defining an actuation link that is expandable and contractable relative to such walls; the third foil having a coefficient of thermal expansion greater than that of the leading foil.

Abstract: A helicoper rotor blade includes at its outer end a tip vane having a mean chord length greater than fifty percent of a chord length of a blade central portion and a span length greater than fifty percent of the blade chord which in operation generates two approximately equal strength tip vortices to reduce an acoustic impulse and a resulting noise known as blade slap.

Abstract: A radiator with a fan is arranged at a forward tilt under the footrest floor part of a cab floor of a cab-over-engine vehicle. The fan confronts the front of the engine. The fan is connected with the radiator through an air duct, a central axis of the air duct rises rearwardly. The fan has at its center a boss shaped into a truncated cone, the extremity of each of the blades in its longitudinal direction being parallel to the axis of the boss. The air duct has one opening end shaped into a cylinder which partially covers the blades of the fan.

Abstract: A compact centrifugal fan that draws air in past the impeller hub, which encloses a motor and which spins about a central axis, and then urges the air through a bend in the fluid passageway. As the air passes through the annular inlet channel about the impeller hub, it flows in a forward axial direction. The air passes through the bend in the fluid passageway, as the air is being swept around the hub by the blades of the impeller. After the air passes through the bend, it has a reverse axial flow component, in addition to a circumferential flow component. Air having a forward axial flow component passes by the portion of an impeller blade that is closest to the impeller hub, and air having a reverse axial flow component passes the portion of a blade that is furthest from the impeller hub.

Abstract: The invention relates to an axial fan with an essentially cylindrical outer housing and with a fan wheel which rotates therein and the hub of which is located on the rotor of an electric drive motor, the stator of the drive motor being held by webs extending on the delivery side relative to the outer housing. The vanes of the axial fan are radially twisted and possess a forward curvature with a camber varying from the hub cross-section to the outer cross-section. In order to achieve a pressure increase, at the same time with a reduction of the operating noise, the vanes have in the hub region a cross-section designed for a low flow per unit volume and small pressure increase, but in the outer region a cross-section designed for higher values of flow per unit volume and pressure increase.

Abstract: An axial flow fan blade (11) having an enhanced tip (12, 12') to reduce or eliminate tip vortices and therefore vortex induced noise. The enhancement is a rounded body extending from the blade tip and having faired ends (15, 16) but otherwise a generally circular cross section. The body conforms to the contour of the tip and extends from the leading to the trailing edge of the blade. The body may have either a generally constant cross section (12) or a cross section that decreases from its leading to its trailing end (12' ).

Abstract: A rotor for an air motor is constructed with a central, milled, aluminum disc having a peripheral flange to which is integrally molded an outer ring of epoxy compound or a composite material, the outer ring defining the series of buckets arranged in an annular ring which are driven by an air nozzle to rotate the rotor. The rotor construction utilizes a combination of old and new materials in a configuration designed to avoid rotor breakup under runaway speed conditions and minimize the damage should such breakup occur.

Abstract: Flow separation behind the notch region of a swept tip of a helicopter rotor blade is reduced by features of the geometry and aerodynamic characteristics of the notch region itself. In particular it has been found beneficial for a forwardly swept leading edge portion to extend at an angle between 30 degrees and 55 degrees from a reference line parallel to a blade pitch change axis and the leading edge of the aerofoil in the notch region incorporates blade droop.

Abstract: A rotor for a screw rotor machine, which rotor comprises a metal shaft (3, 13) and a rotor body (1) of plastics material moulded on the shaft, which is provided with a number of radially extending projections (4) with equal distribution around the shaft, which projections (4) are provided with essentially peripherally extending wings (5) originating from the ridge of the projections (4).

Abstract: A power-producing windmill is disclosed. A paddle assembly having a central axis is supported for rotation on a frame. Two spaced-apart lateral sides supports the central axis and forms a channel in which the paddle assembly rotates. A pivotal vane is connected on one end of the channel for regulating the amount of air entering the channel is operated such as to regulate the rotational speed of the paddle assembly. A unique paddle configuration is provided which provides first and second wind-capturing cavities for increasing the total energy conversion efficiency of the wind to electromotive energy.

Abstract: A propeller blade element which virtually eliminates stall conditions. The rotatably driven blade element employs a long straight extended sharp leading edge from hub to tip, without helix, to insure blade laminar fluid flow without vortice formation or leading edge stagnation. The extending leading edge provides separated upper and lower laminar air flow to a "C" shaped blade configuration. The blade element in one form employs a proportionally upwardly curved trailing edge which provides accelerated flow of the high pressure air on the face of the blade, thus increasing the thrust over conventional blade elements.

Abstract: Dual-plant blade construction for wind turbine rotors having a horizontal shaft having a rotor hub adapted to be mounted on the horizontal shaft and having a horizontal axis. First and second sets of straight blades are secured to said rotor hub in circumferentially equally spaced apart positions on the rotor hub. Each of said sets of blades include first and second blades having tip and root portions with the root portions of the blades being secured to the rotor hub at spaced apart positions along the axis of the rotor hub and the tip portions of the blades being secured to each other whereby there is generated substantially equal and opposite cyclic spanwise forces and minimal cyclic flatwise moments in the first and second blades in response to non-steady aerodynamic normal forces acting on these blades in non-uniform turbulent winds.

Abstract: Impellers and impeller systems are described which enable liquids and liquid suspensions to be mixed and blended where the size of the impeller and the viscosity of the liquid may require operation in the turbulent and laminar flow regimes, as well as in the transitional flow regime therebetween. The impellers have a plurality of fluidfoil blades and have camber and twist. The angle at the tip of two diametrically disposed blades of a four blade impeller may have a different blade angle at the tip than the other pair of blades. A pair of impellers may be used. These impellers may be of different diameter and disposed in close proximity so that they are in dependent relationship (preferably spaced apart by less than the diameter of the larger impeller).

Abstract: A gearless air motor utilizes a high speed rotor having turbine buckets defined in epoxy rather than metal to substantially avoid the danger inherent in high speed rotor fragmentation. The unit has a housing which contains the compressed air chamber, the rotor chamber and a speed reduction chamber in which a toothed belt speed reduction system avoids the use of gears for speed reduction, with their relatively high friction and noise output.

Abstract: A weapon arranged to travel in a given orientation when in flight, has a body and a ribbon. The body has a payload casing and a spindle rotatably mounted at the rear of the payload casing. The ribbon is formed into a flexible loop for trailing behind the body in flight. This ribbon is attached to the spindle. The ribbon has an impelling surface shaped to apply a torque to the spindle when in flight.

Abstract: A hydrodynamic retarder has a stationary element and a rotary element, each of which has a semi-toroidal cavity with a plurality of blade members disposed therein. The semi-toroidal cavities are presented in facing relation with the blade curvatures being oppositely directed. The blade members each have a fluid flow profile that accommodates constant acceleration of the fluid from entrance to exit.

Abstract: An extracorporeal blood pump which comprises a pump housing having a pump chamber defined therein, and a rotary vane assembly accommodated within the pump chamber and including a substantially conical rotary pedestal having a base surface and a conical surface, a plurality of vanes each having radially inner and outer ends, and a driven shaft connected at one end with the base surface of the pedestal. The vanes are mounted on the conical surface so as to extend radially outwardly from an axis of rotation of the pedestal with the radially inner ends of the respective vanes being spaced a predetermined equal distance from an apex of the conical surface while substantially depicting a circle coaxial with the axis of rotation of the pedestal. Each neighboring members of the vanes are equally spaced from each other in a direction circumferentially of the pedestal.

Abstract: A rotary blood pump includes an impeller in a pump chamber driven by a fluid motor. In a first preferred embodiment, the fluid motor includes a rotary member having a series of cupped fluid reactive surfaces that receive a tangential inlet pressurized fluid flow. The cupped surfaces direct the fluid to opposite sides of the rotary member. Passages extending through the rotary member convey fluid from one side of the rotary member to the other. In a second preferred arrangement, the fluid motor is defined by a positive displacement motor. In a third embodiment, the fluid motor is separated from the pump chamber by a wall. Both biocompatible and non-biocompatible fluids can be used to drive the fluid motor.

Abstract: A quiet tail rotor (QTR) blade for helicopters that provides reduced noise levels and increased thrust efficiency. The QTR blade includes a first segment for connecting the QTR blade to a helicopter tail rotor hub and an outboard segment, integral with the first segment, having a configuration that reduces high speed impulsive noise and blade vortex interaction noise and provides increased thrust efficiency. The outboard segment includes an inboard segment integral with the first segment and a swept, tapered tip segment integral with the inboard segment. The inboard segment has a constant chord and a predetermined constant airfoil section profile defined by constant upper and lower surface contours. The predetermined constant airfoil section profile has a t/c ratio greater than about twelve percent of the chord at any station. The swept, tapered tip segment has a variable chord and a predetermined airfoil section profile defined by constant upper and lower surface contours.

Abstract: The known rotor blade for use with axial-flow machines is improved. The improvement resides in a novel configuration of the blade body of the rotor blade. A leading edge of a tip end portion of the blade body is inclined forward (in the upstream direction of flow) and also advances in a direction of rotation, towards a tip end surface of the blade body. In the tip end portion between the tip end surface and a cross section displaced from the tip end surface towards the central portion of the blade body by 1/2 of a chord length of the tip end surface, the configuration of the leading edge of the tip end portion is such that an angle S of skew thereof over which the leading edge of the tip end portion advances in the direction of rotation and an effective skew amount .THETA..sub.s eff thereof of the angle over which the leading edge of the tip end portion is inclined forward in the upstream direction falls in a particular region in a graph of S vs. .THETA..sub.

Abstract: A root attachment for a turbine blade is integrally molded with a composite turbine blade for a ram air turbine. The root attachment includes an insert at the one end of the root attachment for integrally molding within the blade and a hub connector at an opposite end for connecting the blade to a rotor hub. The insert has a geometry and surface area such that a dual load carrying capability is achieved during molding by the formation of an adhesive bond between the material of the blade and the insert and also a mechanical locking which resists failure in bearing. Each of the adhesive bond and the mechanical locking is designed to fail above an ultimate design load.

Abstract: Impellers and impeller systems are described which enable liquids and liquid suspensions to be mixed and blended where the size of the impeller and the viscosity of the liquid may require operation in the turbulent and laminar flow regimes, as well as in the transitional flow regime therebetween. The impellers have a plurality of fluidfoil blades and have camber and twist. The geometric pitch or blade angle increases from the tip of the blade towards their axis of rotation in a manner to provide an over pitched condition so that the pitch ratio of the blades at 40% of the blade radius from the axis is greater than the pitch ratio at the tip. The blades are preferably smoothly tapered and increased in width from the tip towards the axis. The impeller blades are mounted on a hub connected to a drive shaft. The blades may decrease in width where they connect to the hub. The pitch angle at the tip is in the range of 18.degree. to 30.degree. (preferably about 20.degree.).

Abstract: A marine propeller (100) combines progressive pitch with both increasing pitch and increasing progressiveness of pitch along at least a portion of increasing radii from the axis of rotation to the outer blade tip. A five blade propeller is provided which accommodates thermal warpage of the outer blade tips, such that the same propeller includes two different types of blades, one blade having increasing pitch with increasing radii all the way to the outer blade tip, and the other type of blade having increasing pitch to a given radius and then decreasing pitch with increasing radii to the outer blade tip. The latter blade type is preferred and has a hump in the pressure surface at the noted given radius between portions of increasing and decreasing pitch with increasing radii.

Abstract: Stern drive propulsion systems for boats in which there is at least one prime mover (outboard or inboard motor) and a power train for rotating at least one propeller in the water to propel the boat are improved by inclusion therein of novel variable pitch propellers, and a novel pitch adjusting propulsion system. The system includes a blade and hub mechanism that can propel the boat forwardly and in reverse with great maneuverability, and cut through mud and thick vegetation without becoming fouled, as well operate the boat at high speeds in open water.

Abstract: A composite rotor blade comprising an outboard portion defining an airfoil surface, an inboard portion defining an end tang having a mounting section and an extension lug section. The mounting section of the end tang having at least one mounting aperture with an axis parallel to the chordline of the airfoil for mounting of the blade, and the extension lug section having at least one extension lug extending inboard of the mounting aperture to provide a lever surface for interaction with suitable mounting mechanisms.

Abstract: A novel turbine is described which consists of a disc or a shaft, to the upper and lower sides of which blades are attached, the blades on the upper side being at least three times larger than those on the underside. The combination of such a turbine with a guide tube provides a strong suction effect, which is suitable, for example, for drawing gases or gas/vapor mixtures into liquid media. Also, methods of directly heating a liquid by hot gases while avoiding the discharge of pollutants into the environment which comprises introducing the hot gases into the liquid with turbulence and with a suction effect such as, for example, by rotating the turbine in the liquid.

Abstract: In order to increase the lift supporting underpressure force on top of the inlet fairing of a shrouded fan of a lifting engine and in order to reduce the negative lift generating force of the inlet momentum acting on the rotor area of the fan, a particular geometry of the inlet fairing contour in connection with a particular twist of the fan rotor blades (3) is applied. This results in large differences of static pressures between front side and rear side of the fan at outer radii and there will be more small pressure difference at inner radii. This causes an apparent small change of the blade angle .beta. along a mean radial range of the rotor blades. Guide vanes ( 25) which might follow downstream of the fan rotor blades in some design cases, will have an arrangement of radial twist distribution mirror symmetrical to that of the rotor blades.

Abstract: A blade is overtwisted in the extremity zone from at least 0.85R so that the resulting twist is at least equal to a limiting twist .theta.limC according to the plane form Co/C(r) of the blade in this zone and so that the lift coefficient Cz has, in a first fraction of the extremity zone extending at least between r=0/85R and r=0.9R, a decreasing value remaining lower than a first limiting value CZlim1=Czm-a(r/R-b), Czm being the mean lift coefficient of the rotor and a and b being experimental constants, and in a second extremity fraction extending between r=0.9R and at least r=0.95R, the lift coefficient continues to decrease by remaining less than or equal to a second limiting value Czlim2 linearly decreasing from the value Czlim1 for r=0.9R as far as the zero value for r=R.

Abstract: A propeller blade having (i) a planar configuration (ii) an inner end portion, (iii) an outer end portion, (iv) a relatively sharp, outwardly swept back leading edge portion, and (v) a cylindrical stub axially aligned with the plane of the blade and affixed to the inner end portion of the blade. Also described is a mechanism that enables the pitch of the blades to be adjusted by the operator through a continuum of positions ranging from fast forward to fast reverse so that the boat can be operated at a full range and variety of speeds, can be stopped rapidly, and can be maneuvered with precision. The mechanism can be used for operating flat-bottom boats ("mud boats") in swamps, shallow water, bayous, lakes, rivers and the like, and pass through wet mud and swampy marshes choked with mud or vegetation without excessively fouling the propellers. The mechanism can be serviced and repaired easily and quickly, and can be employed to operate small craft such as mud boats with a minimum loss of interior boat space.

Abstract: An impeller formed from sheet-metal by stamping and bending, at a low production cost, capable of delivering an increased quantity of air at a reduced noise level and with reduced power consumption and enhanced efficiency. The method of manufacturing the impeller from sheet metal incorporates sufficient versitility to allow the blades of the impeller to be formed to any desired configuration in order to provide an optimum shape for the intended impeller use. The blades can be curved or twisted and can extend perpendicular from the sheet-metal surface or at any desired angle for optimum utilization.

Abstract: A family of airfoils for use in a high solidity factor blade having a leading edge portion and a trailing edge portion, a tip portion, and a root portion, has a plurality of airfoil sections. Each section has: one of any of a plurality of camber lines extending from the leading edge portion to the trailing edge portion, the camber lines being scalable relative to each other, each having the same relative shape, the camber lines having a minimal slope from the leading edge to about a 40% chord and an apogee at about a 74% chord; a scalable thickness ratio of between about 2% to about 7.5%; and, a maximum thickness position which is located from about a 37.5% chord for an airfoil at the tip portion of the blade to about a 35.0% chord for an airfoil at the root portion of the blade.

Abstract: A clutch fan has a new and unique blade design that results in quieter and more efficient operation. The blade design involves the leading edge having inner, intermediate, and outer regions such that the intermediate region is of increasing skew in the direction of rotation and the outer region is of decreasing skew. The pitch ratio increases as a function of increasing blade radius. Along the outer region, the blade increases in pitch on a defined curvature as a function of blade radius and angle to form a tip curl.

Abstract: An enhanced, air-flow convection oven is disclosed, comprising an oven chamber liner circumscribed by a thermally insulated outer oven shell with a heat source in a combustion chamber between the shell and the liner. Hot air flows from the combustion chamber and into a uniquely constructed blower wheel assembly. The blower wheel assembly has a concave central plate configuration which creates a negative pressure behind the blower wheel assembly, inducing a flow of hot air from the back of the blower wheel assembly into the blower wheel assembly as the wheel rotates. This hot air is mixed with air from within the chamber to produce uniform heating throughout the chamber.

Abstract: A propeller is used to displace a vehicle at a reduced speed but with a high slip of approximately at least 60% and has a quality coefficient of at least 70% for 100% slip. The ratio of the diameter of the propeller to its pitch is approximately 1.18 to 2.9 times the value of the quality coefficient, and the blade width of the propeller is 0.09 to 0.19 times the pitch of the propeller. The propeller pitch is substantially constant and the aerodynamic center of pressure is located at a distance from the propeller axis of rotation equl to approximately 3/4 of the propeller radius. The radius of the curvature of the leading propeller edge, when seen in cross section, is to approximately 1/4 to 1/3 of the greatest blade thickness. In addition the angle of the blade inclination decreases continuously as the propeller diameter increases and the blade thickness is greatest in the leading third of the blade width, relative to the normal rotation direction of the propeller.

Abstract: A propellor (10) for watercraft has a hub (11) with a pair of blades (12) with a leading portion (13) central portion (14) and trailing portion (15). The leading portion (13) of the blades are forwardly inclined relative to the hub (11) and the blades progress through the generally radial central portion (14) to the rearwardly inclined trailing portion (15), the radial height of the blades decreasing from the central portion (14) to the trailing portion (15). Both the peripheral pitch of the blades (12), and the pitch of the line of junction (16) of the blades (12) to the hub (11) increase along the propellor (10), at least from the central portion (14) to the trailing portion (15).

Abstract: This invention relates to a section for shrouded propeller blade, of which the relative thickness is included between 9% and 15%, wherein, the curvature of said section having a maximum value at the leading edge thereof, the upper surface line comprises three successive portions, such thatin the first portion, the curvature decreases rapidly from said maximum value at the leading edge to a value close to 20 at a first point of which the reduced abscissa is close to 1%;in the second portion, the curvature decreases more slowly from said value close to 20 at said first point up to a value close to 1 at a second point, of which the reduced abscissa is close to 25%; andin the third portion, the curvature is less than 1 between said second point and said trailing edge.

Abstract: A family of airfoil cross sections, termed SC21xx, for use in a helicopter blade is disclosed. The airfoil (36) achieves maximum lift performance equivalent to prior art airfoil configurations without incurring increased aerodynamic drag at high velocities. The airfoil (36) was developed by thickening and drooping the leading edge region (38) of the prior art airfoil (30) improving lift in the leading edge region (38) and delaying the formation of sonic shock waves at high velocities.

Abstract: A propeller having blades, designed to achieve maximum thrust at lower static velocities in both forward and reverse pitch modes is disclosed. Each blade has a generous leading edge radius leading to an upper surface having positive camber and a lower surface having positive camber adjacent the leading edge and negative camber adjacent the trailing edge. Each blade also has a high thickness-to-chord ratio and lower span-to-chord ratio or aspect ratio. This thicker blade profile and aft loading leads to a more uniform pressure distribution and laminar airflow across the blade surface resulting in a higher coefficient of lift, increased blade life and reliability, and lower noise levels.