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: 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 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 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: An aircraft propeller blade comprising an inner section which extends from the propeller hub toward the blade tip, a middle section adjacent to said inner section, and an outer section which extends from adjacent to said middle section to the blade tip; where the largest camber in the inner section decreases linearly over the blade length from adjacent to the propeller hub toward the blade tip, and the greatest camber height location shifts linearly over the blade length toward the blade tip; the largest camber in the middle section increases linearly over the blade length toward the blade tip, and the greatest camber height location shifts approximately linearly from adjacent to the inner section toward the blade tip; and the camber in the outer section decreases elliptically over the blade length toward the blade tip, and the greatest camber height location remains constant from adjacent to the middle section to the blade tip.