Embodiments are directed to systems and methods for determining an optimal engine inlet area to minimize spillage drag. An algorithm may utilize aircraft parameters, aircraft performance charts, and engine models to determine the engine inlet area as a function of engine air mass flow, airspeed, and air density at current ambient conditions.

A compact and unobtrusive rotor control mechanism is presented that provides collective and cyclic pitch change to both rotors of a coaxial rotor system as well as a differential collective pitch change to one or both rotors simultaneously.

A propulsion system coupled to a vehicle. The system includes a convex surface, a diffusing structure coupled to the convex surface, and at least one conduit coupled to the convex surface. The conduit is configured to introduce to the convex surface a primary fluid produced by the vehicle. The system further includes an intake structure coupled to the convex surface and configured to introduce to the diffusing structure a secondary fluid accessible to the vehicle. The diffusing structure comprises a terminal end configured to provide egress from the system for the introduced primary fluid and secondary fluid.

Embodiments of the present application relate to the field of propeller technology and specifically disclose 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.

A propulsion system coupled to a vehicle. The system includes an ejector having an outlet structure out of which propulsive fluid flows at a predetermined adjustable velocity. A control surface having a leading edge is located directly downstream of the outlet structure such that propulsive fluid from the ejector flows over the control surface.

An unducted thrust producing system, includes a rotating element, a stationary element. An inlet may be located forward or aft of the rotating element and the stationary element. An exhaust may be located forward, aft, or between the rotating element and the stationary element.

A ducted-fan unmanned aerial vehicle (UAV) capable of low-energy high-rate maneuvers for both vertical roll control and horizontal pitch control. The maneuverability of the UAV is enhanced by equipping the ducted fans with respective piezoelectric-actuated thrust vectoring flaps. Thrust vector control is achieved by controlling the angular positions of a plurality of thrust vector flaps pivotably coupled at respective outlets of a plurality of ducts having fan rotors at the inlets. Each thrust vectoring flap has only one degree of freedom in the frame of reference of the UAV, namely, rotation about a single axis that is perpendicular to the axis of the duct. The angular position of the flap is controlled by sending electrical signals to a piezoelectric actuator (e.g., a piezoelectric bimorph actuator) having a voltage sufficient to cause the piezoelectric actuator to bend.

An aircraft includes a fuselage and an engine housed in the fuselage. A ram-air engine inlet is formed on an exterior of the fuselage. The ram-air engine inlet is defined, at least in part, by a cowling door. The cowling door is moveable between a closed position and an open position. An intake duct fluidly couples the ram-air engine inlet to the engine. A filter is disposed across the intake duct. A bypass duct is formed in the ram-air engine inlet aft of the intake duct. The bypass duct is operable to be selectively opened and closed.

A system and method of an airflow control system for a vehicle is described herein. The airflow control system (100) includes an airflow housing (120) defining an airflow passageway (125) extending between a bypass opening (122) and an intake outlet (124). The airflow housing also defines a duct opening (126) positioned between the bypass opening (122) and the intake outlet (124). The intake outlet (124) may be in fluid communication with an engine intake (12) of the vehicle such that air passes from the bypass opening (122) and/or the duct opening (126) to the engine intake (12). The airflow control system (100) also includes a movable duct (160) movably connected to the airflow housing (120) to selectively allow or prevent air passage through the duct opening (126) and into the engine intake (12), and further includes a bypass door (140) movably connected to the airflow housing (120) to selectively allow or prevent air passage through the bypass opening (122) and into the engine intake (12).

Multi-engine aircraft power plants and associated operating methods are disclosed. An exemplary multi-engine power plant comprises a first turboshaft engine and a second turboshaft engine configured to drive a common load such as a rotary wing of an aircraft; and a heat exchanger in thermal communication with an exhaust gas of the first turboshaft engine and in thermal communication with pre-combustion air of the second turboshaft engine. The heat exchanger is configured to permit heat transfer from the exhaust gas of the first turboshaft engine to the pre-combustion air of the second turboshaft engine.