| CPC F02C 9/40 (2013.01) [F02C 6/08 (2013.01); F02C 7/22 (2013.01); F02C 9/18 (2013.01); F02C 9/26 (2013.01); B64D 2013/0603 (2013.01); F05D 2260/606 (2013.01); F05D 2270/64 (2013.01)] | 19 Claims |

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1. A gas turbine engine for an aircraft comprising:
an engine core comprising a turbine, a combustor, a compressor, and a core shaft connecting the turbine to the compressor;
a fan located upstream of the engine core and arranged to be driven by the core shaft, the fan comprising a plurality of fan blades;
a nacelle surrounding the fan and the engine core and defining a bypass duct located radially outside of the engine core, where a bypass ratio, defined as the ratio of the mass flow rate of the flow through the bypass duct to the mass flow rate of the flow through the engine core at cruise conditions, is at least 4;
a plurality of actuators;
a fuel supply system, wherein the fuel supply system is arranged to supply fuel for combustion in the combustor, and to supply fuel to fueldraulically drive at least one actuator of the plurality of actuators; and
a processor programmed to:
make a determination of sustainable aviation fuel—SAF—content of the fuel, and
based on the determination, control the fuel supply system to select between:
causing the fuel to actuate the at least one actuator; and
causing the fuel to bypass the at least one actuator,
wherein the fuel supply system is arranged to cause the fuel to actuate the at least one actuator when the SAF content is above a threshold, and to cause the fuel to bypass the at least one actuator when the SAF content is below the threshold.
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