Anti-icing stacks for protecting an aerodynamic surface are described. In some embodiments, an anti-icing stack includes an anti-icing layer, an elastomeric erosion protection layer, and an additional layer. The erosion protection layer is disposed between the anti-icing layer and the additional layer. The additional layer has a thickness greater than the thickness of the erosion protection layer and a tensile modulus of no more than the tensile modulus of the erosion protection layer. The additional layer may be a foam adhesive layer.

A turbine engine part coated in at least a first ceramic layer forming a thermal barrier and including a ceramic material with first ceramic fibers dispersed in the first layer. The first layer may have a chemical composition gradient between a material for forming a thermal barrier and a material for providing protection against calcium and magnesium aluminosilicates, which is present at a greater content in an outer zone of the first layer, and/or the first layer may be porous and may present a porosity gradient such that an outer portion of the first layer presents lower porosity.

An aerofoil component is formed of continuous fibre-reinforced polymer composite created by curing laid up pre-preg layers extending in radial and chordal directions of the aerofoil component, and further includes a plurality of Z-pins arranged in a pattern forming a chevron on the pressure and/or suction surface of the aerofoil component, the chevron having a vertex and two arms extending at an angle from each other away from the vertex either towards the radially inner root of the aerofoil component or towards the radially outer tip of the aerofoil component.

A propeller blade comprises a root, a tip distal from the root, a trailing edge extending from the root to the tip, a trailing edge, e.g. foam, insert, a shell forming an outer surface of the propeller blade and a plurality of stitches of yam extending through two parts of the shell adjacent the trailing edge, wherein the yarns do not extend through the trailing edge insert.

A propeller blade assembly includes an airfoil having a base, a tip and a leading edge and a root extending from the base of the airfoil for attaching the airfoil to a hub. The assembly further comprises an electrically conductive sheath for electrically grounding the airfoil. The electrically conductive sheath is attached to the leading edge of the airfoil and extends from the base to the tip of the airfoil. The assembly further comprises an electrically conductive element for electrically connecting the electrically conductive sheath to the root or hub. Also disclosed is an electrically conductive sheath for grounding an airfoil and a method for assembling a propeller blade assembly.

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 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.

A proprotor blade for a ducted aircraft including a duct includes a main body having a distal end and a sacrificial blade tip coupled to the distal end of the main body. The sacrificial blade tip includes a deformable core material and a shell layer at least partially covering the deformable core material. The sacrificial blade tip deforms upon contact with the duct, thereby reducing damage to the ducted aircraft.

A tip gap control system for a ducted aircraft includes a flight control computer including a blade length control module configured to generate a blade tip actuator command and a proprotor system in data communication with the flight control computer. The proprotor system includes a duct and proprotor blades surrounded by the duct. Each of the proprotor blades includes an active blade tip movable into various positions including a retracted position and an extended position. The tip gap control system also includes one or more actuators coupled to the active blade tips. The one or more actuators move the active blade tips between the various positions based on the blade tip actuator command, thereby controlling a tip gap between the proprotor blades and the duct.

A proprotor system for a ducted aircraft includes a duct and proprotor blades surrounded by the duct. Each proprotor blade is rotatable about a respective pitch change axis. The proprotor blades are configured to change collective pitch about the pitch change axes. The proprotor blades are extendable along the pitch change axes into various positions including a retracted position and an extended position. The proprotor blades change between the retracted position and the extended position based on the collective pitch of the proprotor blades, thereby controlling a tip gap between the proprotor blades and the duct.