Abstract: A method of controlling blade pitch angle, including comparing demanded and measured blade pitch angle and calculating any difference therebetween, in a primary electrical control system, where there is a difference, applying torque to a blade pitch regulator to reduce the magnitude of the difference to zero, and in a secondary electrical control system, where the difference is greater than a pre-determined threshold, applying torque to a blade pitch regulator to reduce the magnitude of the difference to the threshold. Also an electrical system of blade pitch angle control for a set of blades including primary and secondary electrical control systems, means for comparing demanded and measured blade pitch angle and calculating any difference therebetween, a look-up function having the difference as its input and outputting a required torque, and a torque regulator to apply the required torque to the set of blades.

Abstract: An engine having at least one stage of propeller rotor blades, and a load, the at least one stage being associated with electrical generation means to generate electricity for the load. The load is switchable into a high load state in the event of an overspeed signal from the rotor blades. Also a method of controlling rotor overspeed of an engine, characterized by the steps of: i. detecting an overspeed signal from the at least one stage, and ii. switching the load into a high load state to apply torque to the at least one stage to counteract the overspeed.

Abstract: A determination of bleed valve activation in a gas turbine engine can be difficult unless the engine is maintained at a steady idle state for comparison between that state and effects of activation of the bleed valve. Furthermore, specific test activation of bleed valves increases wear and tear on those valves. By sensing a flow pressure response signal and then through appropriate averaging and processing through a non-linear filter, it is possible to identify bleed valve activation by a target signal response exceeding a threshold indicative of such bleed valve activation.

Abstract: A method of controlling blade pitch angle, comprising the steps of: comparing demanded and measured blade pitch angle and calculating any difference therebetween, in a primary electrical control system, where there is a difference, applying torque to a blade pitch regulator to reduce the magnitude of the difference to zero, and in a secondary electrical control system, where the difference is greater than a pre-determined threshold, applying torque to a blade pitch regulator to reduce the magnitude of the difference to the threshold. Also an electrical system of blade pitch angle control for a set of blades comprising: primary and secondary electrical control systems, means for comparing demanded and measured blade pitch angle and calculating any difference therebetween, a look-up function having the difference as its input and outputting a required torque, and a torque regulator to apply the required torque to the set of blades.

Abstract: An engine having at least one stage of propeller rotor blades, and a load, the at least one stage being associated with electrical generation means to generate electricity for the load. The load is switchable into a high load state in the event of an overspeed signal from the rotor blades. Also a method of controlling rotor overspeed of an engine, characterised by the steps of: i. detecting an overspeed signal from the at least one stage, and ii. switching the load into a high load state to apply torque to the at least one stage to counteract the overspeed.