Abstract: A rotor for rotary wing aircraft includes a number of features that reduce the collective forces required to control the pitch of the rotor. The spar caps of the spar become joined to one another at the same point where bonding begins between the blade and the spar. The tendency of blade to want to flatten out is minimized since the centrifugal force acting on the spar is located at or near the pitch change axis. Tip weights are located at or near the pitch change axis as well. In a preferred embodiment, the tip weights are located evenly in front of and behind the structural center of the inboard section of the spar. The blade of the rotor and the tip are not swept back.

Abstract: A variable pitch aircraft propeller control uses a two-speed planetary gearbox between a turbine engine and an adjustable pitch propeller. For maximum efficiency, the rotation rate of the propeller is high at aircraft take-off to generate maximum static thrust. However, when at high altitude and at high speed, the propeller rotation rate is reduced to hold the vector sum of the aircraft forward speed and the propeller rotational tip speed at the speed that results in the highest efficiency for the propeller. The two-speed transmission supplies these two gear ratios. At takeoff and low altitude flight, a low gear ratio is used. At high altitude, a high gear ratio is used. The gear ratio maybe manually selected by the pilot, or automatically changed by the propeller controller to obtain the best combined efficiency for the engine and the propeller.

Abstract: A fixed wing rotorcraft uses differential thrust between wing mounted propellers to provide counter torque when the rotor is being powered by a power source. The rotorcraft is comprised of a fuselage to which fixed wings are attached. A rotor is attached on an upper side of the fuselage and provides lift at low speeds while the wings provide a majority of the lift at high speeds. When at high speeds the rotor may be slowed to reduce advancing tip speed and retreating blade stall. Forward thrust and counter torque is provided by propellers mounted on either side of the fuselage or even on the wings.

Abstract: An aircraft landing gear includes a sealed cylinder divided by a cylinder head to define an upper chamber and a lower chamber. The lower chamber is further divided by a piston having a piston rod passing in a sealed manner through the lower cylinder end. The cylinder head includes one or more orifices, the opening of each containing an electromagnetic coil configured to control the viscosity of the magneto-rheological oil passing therethrough. The electrical current through the electromagnetic coil is continually controlled by a microcomputer with attached sensors for piston position and pressure between the desired piston and the cylinder head, such that the pressure between the piston and the cylinder head decelerates the aircraft evenly throughout the desired piston stroke. The pressure also is limited to a desired maximum level so that, in a severe crash, the shock absorber will absorb significant energy before it fails structurally.

Abstract: An improved method of operating rotorcraft capable of achieving high speeds such that stability is maintained as the craft speed exceeds 0.75 times the rotor tip speed. These high speeds are achieved by varying collective pitch, including to negative values, to maintain acceptable levels of flapping at high aircraft forward speeds and low rotor rotation rates, or adjusting or maintaining the rotor rotation rate by automatically controlling the tilt of the rotor disk relative to the airstream or aircraft, or a combination of these techniques. More specifically, by utilizing these techniques the forward aircraft speeds can be high enough, and the rotor rotation rates low enough, that an advance ratio, Mu, greater than 0.75 can be achieved while maintaining rotor stability.

Abstract: A rotor aircraft has an adjusting mechanism that controls the sensitivity of the control stick relative to fore and aft tilt of the rotor. The control stick is pivotable between fore and aft directions as well as laterally about a control stick pivot point. A rotor linkage is connected between the control stick and the rotor rotor head. The rotor linkage assembly tilts the rotor head in response to tilting movement of the control stick. The linkage assembly has a control point that rotates at a radius about the control stick pivot point. An adjusting member located between the control stick and the linkage assembly can be moved to change the radius of the control point to the control stick pivot point. The change in radius corresponds to the amount of tilt that the rotor head make while the control stick moves between full aft and full forward positions. The control stick also controls ailerons and a horizontal stabilizer but these control services are not affected by the adjusting member.

Abstract: A variable pitch aircraft propeller control uses a two-speed planetary gearbox between a turbine engine and an adjustable pitch propeller. For maximum efficiency, the rotation rate of the propeller is high at aircraft take-off to generate maximum static thrust. However, when at high altitude and at high speed, the propeller rotation rate is reduced to hold the vector sum of the aircraft forward speed and the propeller rotational tip speed at the speed that results in the highest efficiency for the propeller. The two-speed transmission supplies these two gear ratios. At takeoff and low altitude flight, a low gear ratio is used. At high altitude, a high gear ratio is used. The gear ratio may be manually selected by the pilot, or automatically changed by the propeller controller to obtain the best combined efficiency for the engine and the propeller.

Abstract: A fixed wing rotorcraft uses differential thrust between wing mounted propellers to provide counter torque when the rotor is being powered by a power source. The rotorcraft is comprised of a fuselage to which fixed wings are attached. A rotor is attached on an upper side of the fuselage and provides lift at low speeds while the wings provide a majority of the lift at high speeds. When at high speeds the rotor may be slowed to reduce advancing tip speed and retreating blade stall. Forward thrust and counter torque is provided by propellers mounted on either side of the fuselage or even on the wings.

Abstract: An airfoil has a concave rear top surface, a concave rear bottom surface, and a rounded trailing edge to increase the lift-to-drag ratio of the airfoil at small angles of attack when air is flowing from the trailing edge to the leading edge (reverse flow), while maintaining a high lift-to-drag ratio when air is flowing from the leading edge to the trailing edge (forward flow). The airfoil design results from a performance compromise between forward and reverse airflow. For structural reasons, the thickness of the airfoil in proportion to its chord length may change along the blade radius. Thus, a family of airfoils has been designed that promote low-drag laminar flow with both forward and reverse flow, permit operation of the airfoil with reverse flow over a reasonable range of angles of attack, and achieve high lift with forward flow.

Abstract: A method of operating a rotor aircraft at high speeds applies negative collective pitch to the rotor. The rotor aircraft has a wing, a thrust source and a rotor. During horizontal flight, the pilot operates the thrust source to move the aircraft forward. This supplies lift due to air flowing over the wing. By controlling tilt of the rotor, and without supplying power to the rotor, the pilot causes the rotor to auto-rotate due to the forward movement of the aircraft. The speed of rotation of the rotor is controlled by the degree of tilt of the rotor relative to the direction of flight. Once the aircraft speed is sufficiently high to cause reverse flow of air over the entire retreating blade of the rotor, the pilot reduces the collective pitch of the rotor to less than zero to reduce the flapping as desired.

Abstract: A rotor for rotary wing aircraft includes a number of features that reduce the collective forces required to control the pitch of the rotor. The spar caps of the spar become joined to one another at the same point where bonding begins between the blade and the spar. The tendency of blade to want to flatten out is minimized since the centrifugal force acting on the spar is located at or near the pitch change axis. Tip weights are located at or near the pitch change axis as well. In a preferred embodiment, the tip weights are located evenly in front of and behind the structural center of the inboard section of the spar. The blade of the rotor and the tip are not swept back.

Abstract: An aircraft landing gear includes a sealed cylinder divided by a cylinder head to define an upper chamber and a lower chamber. The lower chamber is further divided by a piston having a piston rod passing in a sealed manner through the lower cylinder end. The cylinder head includes one or more orifices, the opening of each containing an electromagnetic coil configured to control the viscosity of the magneto-rheological oil passing therethrough. The electrical current through the electromagnetic coil is continually controlled by a microcomputer with attached sensors for piston position and pressure between the desired piston and the cylinder head, such that the pressure between the piston and the cylinder head decelerates the aircraft evenly throughout the desired piston stroke. The pressure also is limited to a desired maximum level so that, in a severe crash, the shock absorber will absorb significant energy before it fails structurally.

Abstract: A propeller for aircraft has a tip-to-tip flex-beam spar and torsionally stiff hollow blades bonded to the spar throughout an outer portion of the blades. The spar has two end caps which are separated from each other at the hub and converge in the outer portion. The blades have an inner region which is not bonded to the spar, allowing an inner portion of the spar to twist during pitch changes. A counterweight is mounted to an arm extending from an inner end cuff of each blade. The counterweight is located out of the plane of rotation. The counterweight is also located on a side of a line opposite from the trailing edge, the line passing through the pivot axis perpendicular to the plane of rotation.

Abstract: A rotary wing aircraft has an engine, an engine-driven shaft and a main rotor. A rotor drive shaft is mounted to the main rotor and extends substantially 90 degrees to the engine-driven shaft. A drive pulley is mounted to the engine-driven shaft. A driven pulley is operatively coupled to the rotor drive shaft. A drive belt extends around the drive and driven pulleys. A fluid cylinder has one end stationarily mounted to the engine and another end operatively coupled to the driven pulley to selectively move the driven pulley away from the drive pulley. This movement applies tension in the belt to cause the drive pulley to rotate the main rotor.

Abstract: A rotor for rotary wing aircraft has a tip to tip flex-beam spar and torsionally stiff hollow blades bonded to the spar throughout the tip-most portion of the blades. The spar spaced-apart spar caps which have a dual beam cross section in the region not bonded to the blades so that the spar is twistable for pitch control. The rotor spindle and controls pass through a central hole between the spar caps. An intermediate section of the rotor has shear webs bonded above and below spaced-apart spar caps, providing a stiff box beam cross section. The spar caps join each other outboard of the intermediate section. The collective control for pitch change employs a coil spring mounted between a pitch horn and a hub.

Abstract: A shock absorber, optionally operable as a retractable landing gear actuator, includes a sealed cylinder divided by a cylinder head to define an upper chamber and a lower chamber, the lower chamber further divided by a piston having a piston rod passing in sealed manner through the lower cylinder end. The cylinder head includes one or more orifices, the effective opening of each orifice controlled by a valve, the valve having a stem attached to and passing through the upper cylinder end to the atmosphere, such that the pressure between the piston and the cylinder head is limited to a certain value above atmospheric pressure, regardless of the velocity or position of the piston. The valve is forced toward the closed position by a spring against a stop such that it is always at least partially open. During hard or crash landings, high fluid pressure on the piston or in the upper chamber forces the valve further open.

Abstract: A fuselage door for a pressurized aircraft fuselage in which the hoop tension loads caused by cabin pressure are carried through the door rather than around the door. Stationary interlocking moldings in the door and fuselage door seat transfer loads through the door-fuselage intersection. The interlocking portions of the moldings have a sloped engaging portion having an angle such that the inward directed force component of tension due to a pressure differential is less than the outward directed force from cabin pressure on the door.

Abstract: An aircraft of the type having retractable landing gear and a pusher propeller is provided with a twin tail boom. The tail boom has a configuration to prevent the lowermost point of the pusher propeller from contacting a landing surface when landing the aircraft, even with the landing gear retracted, so that the engine of the aircraft is not damaged as a result of the pusher propeller being unable to rotate during the landing.

Abstract: A flexible beam rotor assembly for an aircraft includes a rotor spar having an axis of rotation and a hole through which the axis of rotation passes. A spindle has a teetering connection to the rotor spar, the teetering connection having a teetering axis above the rotor spar at the rotor axis of rotation. A spindle housing is nonrotatably mounted to the aircraft and rotatably receives the spindle. The spindle housing and spindle protrude through the hole in the rotor spar and are tiltable in response to pilot control on a left-right spindle pivot axis and a fore-aft spindle pivot axis. The left-right spindle pivot axis and the fore-aft spindle pivot axis are located below the teetering axis and above the rotor at the rotor axis of rotation. A pylon is pivotally mounted to the fuselage for fore and aft movement relative to the fuselage to absorb vibration due to rotation of the rotor during forward flight of the aircraft. The spindle housing is attached to the pylon by a universal joint.

Abstract: An improved gyroplane having an improved rotor blade with an edgewise stiffness (El) of at least 80,000 pounds inch.sup.2 per pound of aircraft gross weight and blade weights of sufficient size to store a minimum of 100 foot pounds of rotational kinetic energy per pound of gross weight of the gyroplane while the rotor blade pitch is set to minimum lift during blade prerotation. Then a clutch driving the rotor is disengaged and the rotor blade pitch is changed to a lift condition to enable the gyroplane to climb to an altitude of at least fifty feet. The speed and thrust of a propeller is increased to achieve an increasing a horizontal velocity to maintain altitude, first with the rotor blade providing most of the lift and until the wings provide all the lift. To maximize velocity an improved flight control method is utilized. With this method, the angle of attack of the rotor disc is decreased and the pitch of the rotor blade is reduced to decrease rotor blade rotational speed to minimize drag during flight.