A fuel system includes a fuel metering unit having a fuel inlet and a fuel outlet defining a flow path therebetween. The fuel system includes a bleed valve in fluid communication with the flow path of the fuel metering unit. The fuel system includes a controller in communication with the fuel metering unit and the bleed valve to send data thereto and/or receive data therefrom. The bleed valve is configured and adapted to open or close depending on a command from the controller. The flow path is configured and adapted to be in selective fluid communication with a fuel system interstage through the bleed valve.

A fuel system includes a fuel metering unit having a fuel inlet and a fuel outlet defining a flow path therebetween. The fuel system includes a bleed valve in fluid communication with the flow path of the fuel metering unit. The fuel system includes a controller in communication with the fuel metering unit and the bleed valve to send data thereto and/or receive data therefrom. The bleed valve is configured and adapted to open or close depending on a command from the controller. The flow path is configured and adapted to be in selective fluid communication with a fuel system interstage through the bleed valve.

A method for controlling a gas turbine assembly includes: a compressor in which compression of the outside air occurs for producing a flow of compressed air; a sequential combustor including a first combustor, in which combustion of a mixture of fuel and compressed air arriving from the compressor occurs for producing a flow of hot gasses, and a second combustor which is located downstream of the first combustor and in which combustion of a mixture of fuel and hot gasses arriving from the first combustor occurs; an intermediate turbine in which a partial expansion of the hot gasses arriving from the first combustor occurs; and a second combustor in which combustion of a mixture of fuel and hot gasses arriving from the intermediate turbine occurs; the method further includes, on a start-up transient operating phase of the gas turbine assembly, the step of controlling the fuel mass flow-rate supplied to the first and/or the second combustor on the basis of the flame temperature inside the first combustor.

A method for controlling a gas turbine assembly includes: a compressor in which compression of the outside air occurs for producing a flow of compressed air; a sequential combustor including a first combustor, in which combustion of a mixture of fuel and compressed air arriving from the compressor occurs for producing a flow of hot gasses, and a second combustor which is located downstream of the first combustor and in which combustion of a mixture of fuel and hot gasses arriving from the first combustor occurs; an intermediate turbine in which a partial expansion of the hot gasses arriving from the first combustor occurs; and a second combustor in which combustion of a mixture of fuel and hot gasses arriving from the intermediate turbine occurs; the method further includes, on a start-up transient operating phase of the gas turbine assembly, the step of controlling the fuel mass flow-rate supplied to the first and/or the second combustor on the basis of the flame temperature inside the first combustor.

A system for operating a gas turbine engine to mitigate the risk of ice formation within the engine, the system including a controller arranged to control at least one operational parameter of the engine such that the engine operates in a safe zone; and, a processor configured to function as a determining module to make a comparison between values and determine whether the engine is operating within a safe zone based on at least a core pressure parameter relating to the pressure within the engine and a core temperature parameter relating to the temperature within the engine, wherein the safe zone is defined by the product (multiplied) of the core pressure parameter and core temperature parameter being above a safe threshold.

A system for operating a gas turbine engine to mitigate the risk of ice formation within the engine, the system including a controller arranged to control at least one operational parameter of the engine such that the engine operates in a safe zone; and, a processor configured to function as a determining module to make a comparison between values and determine whether the engine is operating within a safe zone based on at least a core pressure parameter relating to the pressure within the engine and a core temperature parameter relating to the temperature within the engine, wherein the safe zone is defined by the product (multiplied) of the core pressure parameter and core temperature parameter being above a safe threshold.

A turbine arrangement for a gas turbine engine comprising a turbine shaft. An axial array of turbine rotors, having a first axial end and a second axial end. A drive arm coupled between the turbine shaft and the first axial end. A measurement system arranged to measure a parameter of the turbine arrangement, the measurement system positioned at the second axial end. The parameter may be rotational speed.

A turbine arrangement for a gas turbine engine comprising a turbine shaft. An axial array of turbine rotors, having a first axial end and a second axial end. A drive arm coupled between the turbine shaft and the first axial end. A measurement system arranged to measure a parameter of the turbine arrangement, the measurement system positioned at the second axial end. The parameter may be rotational speed.

A pressure balanced thermal actuator includes a flow housing having an inlet and an outlet, with the flow housing being affixed at opposing ends to two bellows housings, each of which contains a bellows. An actuation rod is operably coupled to each bellows and contains a fluid passage therewithin. When the temperature of the area surrounding the actuator increases, the pressure inside the bellows housings increases, and exerts a force on the bellows therein, compressing it. As a result, the actuation rod moves from a first position to a second position to align the fluid passage with the inlet and the outlet, enabling the controlled passage of a first fluid from the inlet, and through the fluid passage, to the outlet, to reduce the temperature of the area surrounding the valve assembly. The actuator is unaffected by changes in the ambient pressure, by working equally on two opposing bellows areas.

The present application discloses a method of determining one or more fuel characteristics of an aviation fuel used for powering a gas turbine engine of an aircraft. The method comprises: determining one or more performance parameters of the gas turbine engine during a first time period of operation of the gas turbine engine; and determining one or more fuel characteristics of the fuel based on the one or more performance parameters. A method of operating an aircraft, a fuel characteristic determination system, and an aircraft are also disclosed.