Abstract: A bearing arrangement, for example, for a variable pitch propeller, has a fluid operated actuator (42, 34, 40) for causing relative movement between bearing surfaces of races (12, 32) so as to preload bearings (30) held there between. Mechanical locking means (34, 36, 38) is provided to maintain the bearings under preload when the fluid pressure is released from the actuator.

Abstract: The sealing ring seals between relatively rotating and vibrating machine parts such as parts of an aircraft propeller, and has several sealing lands. The shape and configuration of the lands are selected so that natural vibration frequencies of the ring or lands are not vibration frequencies to which the ring is subject in use.

Abstract: A sliding contact bearing, especially an aircraft landing gear trunnion beating, comprises two bearing members (1, 3) composed of titanium or titanium alloy with cooperating sliding surfaces (2, 4), a first one of which is chromium plated and the second one of which is coated with nickel and fluorocarbon polymer. Preferably, the nickel coating is applied by an electroless plating process, and the fluorocarbon is infused into pores in the nickel plating. Preferably, the nickel and fluorocarbon coating is 0.025 to 0.041 mm thick, and has a hardness in the range 750-1000 VPN.

Abstract: A propeller comprises a hub (1) rotatable about a propeller axis and formed with a hub barrel (1) with a central hub axis that extends radially of the propeller axis, a blade (9) having a support assembly (3) at its inner end received within the hub barrel (1) and including at least one bearing (11,16) that supports the blade (9) for rotation about the hub axis, a locking recess (7,25,33) formed at least in part in the support assembly (3) and at least in part in the hub barrel (1) and a key element (26) located within the locking recess (7,25,33) to restrain radial outwards movement of the blade (9) along the hub axis. The key element (26) is insertable into and retractable from the locking recess (7,25,33) while the inner end of the blade (9) is assembled in the hub barrel (1). The locking recess (7,25,33) extends circumferentially within the hub barrel (1), and the key element (26) is flexible to follow the recess when inserted.

Abstract: A pressure relief valve includes a fluid flow channel (6, 19, 21) through which an initial flow of fluid passes in use, and a valve opening member (23) responsive at a predetermined fluid pressure to open the valve (13) and allow an increased fluid flow therethrough. The valve opening member (23) is located substantially centrally in the fluid flow channel (6, 19, 21) to ensure it is always exposed to the fluid flow. Part of the flow channel (21) is formed by part of the valve (13). The valve opening member (23) and flow channel (21) are elongated and parallel. A screen (13) on the valve screens the outlet end of the channel (21) from the fluid inlet port (6).

Abstract: A servosystem comprising an adaptive digital controller (1) with an input signal (r.sub.t), an output control signal (u.sub.t) to the system (2) being controlled, and an input feedback signal (y.sub.t) from the system being controlled, the controller (1) incorporating an estimator (3) which operates recursively in response to the output control signal (u.sub.t) and feedback signal (y.sub.t) to estimate the values of parameters of a predetermined mathematical model (4) of the system being controlled and which makes use of a forgetting factor (.lambda.) to weight previous values of said parameters before these values are used in combination with current values of said output control and feedback signals (u.sub.t, y.sub.t) in each recursive estimation cycle, said output control signal (u.sub.

Abstract: A cover provided for covering a bladed rotor during a testing operation. The cover has a face plate of solid sheet like material having a centrally positioned orifice through which air is drawn by the action of part of blade adjacent to orifice. The remaining part of the blades is in a stalled condition and therefore relatively unloaded. The power required to turn the rotor is therefore reduced in comparison to that required if the cover was not present making testing easier. The cover also acts as a safety shroud preventing personnel coming into contact with the blades as they rotate and containing the rotor in the event of its disintegration.