A main rotor blade 1, which is the main rotor blade 1 for a high-velocity helicopter, includes: a blade root part 10 having a length of 30% or more of a rotor radius R; and a blade main body 20 continuous with the blade root part 10. Preferably, a cross-sectional shape of the blade root part 10 satisfies (x/a).sup.m+(y/b).sup.m=1 and a>b, where m: arbitrary number, x: chord length direction, and y: blade thickness direction.

Disclosed is an electrically driven ducted fan engine, comprising a housing with an inner housing wall, defining a substantially cylindrical inner space and a longitudinal axis, an inlet opening, a rotor with a multitude of rotor blades positioned in the inner space of the housing downstream of the inlet opening, a stator assembly with a multitude of guide vanes extending from a radially central region of the inner space to the inner wall of the housing, and an exhaust opening provided in the housing downstream of the stator assembly, an interstage region defined between the rotor and the stator assembly, a guide vane region defined in which guide vanes extend to the inner wall of the housing and an exhaust section, wherein in at least one of the interstage region, the guide vane region and the exhaust region, acoustic liners are provided to the housing.

A low-cost rocket includes an atmospheric flight part and an exo-atmospheric flight part, and uses the atmospheric air part to ascend into the atmosphere through the use of propellers for the atmospheric portion of the flight. The atmospheric flight part separates from the exo-atmospheric flight part in the vicinity of the exo-atmosphere and the exo-atmospheric rocket is launched thereupon. The atmospheric flight part descends through the atmosphere using autorotation of the propellers and, if necessary, a soft landing can be affected by controlling the pitch of the propellers just prior to landing.

A foldable propeller for air mobility includes a link assembly including a plurality of links facilitating blades to be rotated around a hub as a moving portion vertically slides such that the blades are folded to each other or unfolded from each other.

A propeller, a propeller kit, a power assembly, a power kit and an unmanned aerial vehicle (UAV). The propeller includes a hub and at least two blades connected to the hub. The hub is detachably mounted on a corresponding drive apparatus by a mounting member corresponding to the hub, so that the propeller is mounted on the corresponding drive apparatus. A surface, facing the mounting member, of the hub is provided with a first fitting portion. A surface, facing the hub, of the mounting member is provided with a second fitting portion corresponding to the first fitting portion. The first fitting portion matches the second fitting portion. In the foregoing manner, a user can be prevented from incorrectly mounting a forward propeller and a counter-rotating propeller during the use of a quick-detachable propeller in the embodiments of the present application.

An aircraft system includes a propulsion system structure, a variable area nozzle and a linkage system. The propulsion system structure is moveable between a first position and a second position. The variable area nozzle is fluidly coupled with a duct in the propulsion system structure. The variable area nozzle is moveable between a first configuration and a second configuration. An exit area of the variable area nozzle has a first value when the variable area nozzle is in the first configuration and a second value when the variable area nozzle is in the second configuration. The variable area nozzle includes a flap moveably connected to the propulsion system structure. The linkage system mechanically links the variable area nozzle with the propulsion system structure. The linkage system includes a driver linkage, a first bell crank, a bridge linkage, a second bell crank, a follower linkage and a crank arm.

A propeller, a propeller kit, a power assembly, a power kit and an unmanned aerial vehicle (UAV). The propeller includes a hub and at least two blades connected to the hub. The hub is detachably mounted on a corresponding drive apparatus by a mounting member corresponding to the hub, so that the propeller is mounted on the corresponding drive apparatus. A surface, facing the mounting member, of the hub is provided with a first fitting portion. A surface, facing the hub, of the mounting member is provided with a second fitting portion corresponding to the first fitting portion. The first fitting portion matches the second fitting portion. In the foregoing manner, a user can be prevented from incorrectly mounting a forward propeller and a counter-rotating propeller during the use of a quick-detachable propeller in the embodiments of the present application.

The present invention relates generally to propulsion systems and, more specifically, to propulsion systems configured to vector and provide directional thrust such as those that may be used in aircraft or watercraft. Such propulsion systems may be used in connection with unmanned aerial vehicles, other aircraft, or various watercraft including submersibles.

A method of assembling an aircraft gearbox. The method includes mounting an outer race and a plurality of rollers of a roller bearing in an opening of a gearbox housing, mating a cylindrical guide sleeve having a lead-in chamfer with a gear assembly having a gear and a cylindrical shaft such that a trailing shoulder of the guide sleeve is positioned proximate a leading shoulder of the shaft, the shaft including an inner race of the roller bearing, axially passing the lead-in chamfer of the guide sleeve through the plurality of rollers, radially outwardly urging the rollers toward the outer race with the guide sleeve, axially passing the leading shoulder of the shaft through the plurality of rollers, positioning the inner race relative to the plurality of rollers to form the roller bearing and removing the guide sleeve from the gear assembly.

A blade pitch adjustment mechanism includes a pitch cylinder having a first face and pitch slots extending longitudinally from the first face, a blade sleeve having a second face and a blade slot extending longitudinally from the second face, the blade sleeve is configured to be rotationally positioned in the pitch cylinder with the second face located with the first face, wherein the blade slot and the pitch slots are cooperative to form keyway, corresponding to a discrete blade pitch, when the blade slot is aligned with a pitch slot.