Abstract: A propeller control system (1) includes a propeller controller (6) the gain of which is set by a look up table (2) in response to airspeed data supplied by an airspeed detector (4). By varying the gain of the propeller controller (6) an overall system gain can be maintained as the gain of a propeller (7) varies with airspeed.

Abstract: A propeller control system comprises a phase controller (11) having a phase control gain to control a propeller phase relationship, free air turbulence detection means (7, 9) and a gain controller (8) for varying the phase control gain in response to detected free air turbulence such that in the presence of turbulence a low gain is selected and in the absence of turbulence a high gain is selected. By varying the gain in this way the sensitivity of the phase controller (11) is reduced during turbulent conditions preventing excessive phase changes by the controller (11) striving to follow a turbulent master propeller. Similarly a speed controller (14) has its gain set by a gain controller (17) according to the degree of turbulence detected.

Abstract: A bladed rotor assembly comprising:a bladed rotor;an actuator for effecting a change of blade pitch;a first valve member connected to, and movable with, the actuator and having first and second passageways;anda second valve member co-operable with the first valve member and having first and second passageway systems formed therein for communication with the first and second passageways of the first valve member.The first passageway system of the second valve member includes first and second independent passageways, and is provided with a valve, and a bypass incorporating a non return valve. The valve is positioned so that when in a closed position fluid is prevented from entering the first independent passageway.