A method of mitigating contrails produced by an aircraft having a set of gas turbine engines, comprises the steps of (i) for each engine in a first subset of the engines, reducing the operating efficiency of the engine to produce a reduction in thrust provided by that engine and (ii) for each engine in a second subset, increasing the fuel flow to the engine to increase the thrust provided by that engine, the set of at least two gas turbine engines consisting of the first and second subsets. The method provides for contrail mitigation action by means of engine operating efficiency reduction to be directed to a first subset of engines for which contrail mitigation per unit engine operating efficiency reduction is greatest, the resulting reduction in thrust provided by such engines being at least partially compensated by increasing fuel flow to engines of the second subset.

A method of mitigating contrails produced by an aircraft having a set of gas turbine engines, comprises the steps of (i) for each engine in a first subset of the engines, reducing the operating efficiency of the engine to produce a reduction in thrust provided by that engine and (ii) for each engine in a second subset, increasing the fuel flow to the engine to increase the thrust provided by that engine, the set of at least two gas turbine engines consisting of the first and second subsets. The method provides for contrail mitigation action by means of engine operating efficiency reduction to be directed to a first subset of engines for which contrail mitigation per unit engine operating efficiency reduction is greatest, the resulting reduction in thrust provided by such engines being at least partially compensated by increasing fuel flow to engines of the second subset.

A gas turbine engine fuel supply system can include a fuel delivery system, a thermal management system, a fuel manifold, and one or more sensors that identify one or more fuel parameters. A fuel control system adjusts parameters of the fuel based on data received from the sensors.

A gas turbine engine fuel supply system can include a fuel delivery system, a thermal management system, a fuel manifold, and one or more sensors that identify one or more fuel parameters. A fuel control system adjusts parameters of the fuel based on data received from the sensors.

An engine system of an aircraft includes a gas turbine engine comprising at least one spool and at least one electric machine operably coupled with the at least one spool. A controller is configured to detect if the at least one spool of the gas turbine engine is in or is approaching an overspeed condition and apply a load to the at least one spool via the at least one electric machine.

An engine system of an aircraft includes a gas turbine engine comprising at least one spool and at least one electric machine operably coupled with the at least one spool. A controller is configured to detect if the at least one spool of the gas turbine engine is in or is approaching an overspeed condition and apply a load to the at least one spool via the at least one electric machine.

A gas turbine engine for an aircraft. The gas turbine comprises a combustor, a fuel injection system connected with a source of fuel and configured to inject fuel into the combustor, a water injection system connected with a source of water and which is configured to inject water into the combustor, and a control system. The control system is configured to identify an atmospheric condition; determine a water-fuel ratio for injection into the combustor of the gas turbine engine in response to the atmospheric condition; and control injection of fuel and water by the fuel injection system and the water injection system according to said water-fuel ratio to control an soot emissions caused by combustion of fuel therein.

A gas turbine engine for an aircraft. The gas turbine comprises a combustor, a fuel injection system connected with a source of fuel and configured to inject fuel into the combustor, a water injection system connected with a source of water and which is configured to inject water into the combustor, and a control system. The control system is configured to identify an atmospheric condition; determine a water-fuel ratio for injection into the combustor of the gas turbine engine in response to the atmospheric condition; and control injection of fuel and water by the fuel injection system and the water injection system according to said water-fuel ratio to control an soot emissions caused by combustion of fuel therein.

An operation management device includes a state acquiring unit that acquires a measurement value of a first state amount indicating an operation state of a power generation plant, a state updating unit that updates an estimation value of a second state amount, which indicates the operation state of the power generation plant and is a state amount different from the first state amount, based on the measurement value of the first state amount, and a managing unit that manages the operation state of the power generation plant based on the estimation value of the second state amount.

An operation management device includes a state acquiring unit that acquires a measurement value of a first state amount indicating an operation state of a power generation plant, a state updating unit that updates an estimation value of a second state amount, which indicates the operation state of the power generation plant and is a state amount different from the first state amount, based on the measurement value of the first state amount, and a managing unit that manages the operation state of the power generation plant based on the estimation value of the second state amount.