A rotating system comprising two or more blades 3 mounted on a hub installed on a rotatable propeller shaft 1, each blade provided with a respective sensor 4 arranged to detect response of the respective blade to harmonic excitation; and the system further comprising means configured to compare the response of the respective blade to that of the other blade(s).

The present disclosure provides a method and system for determining a helicopter rotor airfoil. The method includes: randomly generating a sample point by using a Latin hypercube sampling (LHS) method (S1); determining characterization equations of upper and lower airfoil surfaces of an airfoil based on the airfoil sample point by using a class shape transformation (CST) method (S2); performing dynamic characteristic simulation on the airfoil according to the characterization equations of the upper and lower airfoil surfaces by using a computational fluid dynamics (CFD) method, to obtain a flow field characteristic of the airfoil (S3); establishing a mapping relationship between the sample point and the flow field characteristic by using a Kriging model, and training the mapping relationship by using a maximum likelihood estimation method and an expected improvement (EI) criterion, to obtain a trained mapping relationship (S4); determining an optimal sample point based on the trained mapping relationship by using Non-dominated Sorting Genetic Algorithm II (NSGA-II) (S5); and determining a rotor airfoil based on the optimal sample point (S6). The method performs optimized design on aerodynamic characteristics of the airfoil in a state with a changing incoming flow and a changing angle of attack, and can effectively alleviate dynamic stall in this state.

Provided are reactive compositions for making a polyurethane-based rain-erosion protective coating for rotor blades, the reactive composition comprising an isocyanate-reactive component and an isocyanate-functional component and wherein the isocyanate-reactive component comprises a first component i) being a short chain hydroxyl-functional compound having two terminal (α-ω) hydroxyl groups, a molecular weight of less than 250 g/mole and containing at least 2 carbon atoms and a second component ii) comprising a high molecular weight hydroxyl-functional compound having two terminal (α-ω) hydroxyl groups and a molecular weight of at least 250 g/mol and comprising one or more units selected from oxyalkylene units and polyoxyalkylene units and wherein the isocyanate-functional component is an isocyanate prepolymer of the general formula NCO—Z—NCO, wherein Z is a linking group comprising at least two urethane (—NH—CO—O—) units and additionally one or more units selected from alkylenes, oxyalkylenes, polyoxyalkylenes, alkylene esters, oxyalkylene esters, polyoxyalkylene esters and combinations thereof. Also provided are protective coatings obtained from the reactive compositions and methods of applying the coatings to articles.

A rotor assembly for a rotary wing aircraft includes a rotor hub having a central axis. The rotor hub is rotatable about the central axis. A plurality of flexible structural members extend radially outwardly from the rotor hub. Each flexible structural member is substantially U-shaped having a first arm extending from the hub, a second arm extending from the hub, and an end portion connecting the first arm to the second arm at a radially outboard end of the flexible structural member. The first arm, the second arm and/or the end portion have a cross section with a height along the central axis greater than a thickness of the cross section to increase stiffness of the rotor assembly along the central axis. The rotor assembly further includes a plurality of rotor blades, each rotor blade being secured to each flexible structural member of the plurality of flexible structural members.

A rotor assembly for a rotary wing aircraft includes a rotor hub having a central axis. The rotor hub is rotatable about the central axis. A plurality of flexible structural members extend radially outwardly from the rotor hub. Each flexible structural member is substantially U-shaped having a first arm extending from the hub, a second arm extending from the hub, and an end portion connecting the first arm to the second arm at a radially outboard end of the flexible structural member. The first arm, the second arm and/or the end portion have a cross section with a height along the central axis greater than a thickness of the cross section to increase stiffness of the rotor assembly along the central axis. The rotor assembly further includes a plurality of rotor blades, each rotor blade being secured to each flexible structural member of the plurality of flexible structural members.

A propeller blade for rotation about a hub assembly is provided, wherein the propeller blade defines a radial direction along its length from a blade root to a blade tip, the propeller blade including a radially inner region, a radially outer region located between the blade root and the blade tip at a position where rotational forces on the blade are sufficient, in use, to remove ice from an uncoated blade, a coating disposed at least along a leading edge of the propeller blade, the coating including an icephobic material, wherein the coating extends along the propeller blade from the radially inner region to the radially outer region.

Sounds are generated by an aerial vehicle during operation. For example, the motors and propellers of an aerial vehicle generate sounds during operation. Disclosed are systems, methods, and apparatus for actively adjusting the position and/or configuration of one or more propeller blades of a propulsion mechanism to generate different sounds and/or lifting forces from the propulsion mechanism.

A device to absorb kinetic energy caused by an exceptional load includes an outer casing configured to maintain integrity after the exceptional load. A core of the device is made of a compactable material at least partially filling the outer casing. The core material is compacted under an exceptional load and absorbs some of the kinetic energy caused by the load. At least one stiffness element is incorporated into the core. A distribution element includes each stiffness element. An aircraft, a vehicle, an item of equipment and an installation includes such a device.

A propeller having a means for creating fluid flow in a non-axial direction and redirecting it in an axial direction.

A blade is provided for the cycloidal marine propellers or cycloidal aerial rotors. Said blade is provided with the capabilities, in response to the control system commands to dynamically and in real time; flex itself along its chord in any required way, vary its relative pivot point position, change its planform by extending or retracting a trailing edge extension, differentially if needed on the right and left, turn the flap along the trailing edge in either direction or allow it to be turned by the flows. Said blade is also optionally provided with one or more elastic trailing edges whose stiffness is dynamically, and possibly differentially along the blade span, variable by the control system. For the reversal of the leading and trailing edges for operation in reverse airflow and other conditions the blades are provided with edges that can be made rigid when functioning as the leading edge and flexible if needed when functioning as the trailing edge. Also the blades are provided with the capability of varying their cross-sectional profile thickness and reshaping it. Finally the blades are given on command flow permeability along much of their surface. These capabilities will enable each control system controlled blade to continually optimally adjust to and make the best use of its immediate operating environment as it travels along its trajectory within each revolution.