A control device includes a fuel equivalent value calculation unit for determining the flow rate of fuel supplied to a gas turbine in accordance with a target value deviation between an actual rotation speed and a target rotation speed, an upper limit deviation calculation unit for obtaining an upper limit deviation which is a deviation between a set upper limit output and an actual output, a lower limit deviation calculation unit for obtaining a lower limit deviation which is a deviation between a set lower limit output and the actual output, and a parameter-changing unit for changing any one parameter among the target rotation speed, the actual rotation speed, and the target value deviation so that the target value deviation decreases when the actual rotation speed decreases and the upper limit deviation is small, and so that the target value deviation increases when the actual rotation speed increases and the lower limit deviation is small.

A fuel system for a gas turbine engine configured to combust hydrogen fuel. The fuel system includes a main fuel conduit, a fuel pump configured to operate on hydrogen within fuel conduit to provide pressurised fuel to core combustor of gas turbine engine, an auxiliary combustor downstream in fuel flow of fuel pump, and configured to combust a portion of fuel diverted from main fuel conduit and to heat remainder of fuel in main fuel conduit, and a fuel turbine downstream in fuel flow of the auxiliary combustor. The fuel turbine is configured to be driven by heated fuel from auxiliary combustor and configured to power the fuel pump. The fuel system comprises a turbine inlet valve provided upstream in hydrogen fuel flow of the fuel turbine and configured to control mass flow rate and/or pressure of fuel flowing into fuel turbine. 1. A method of operation is also described.

An assembly for an aircraft includes a fluid source, a first heat exchanger, a partial-admission turbine, a mechanical load, and a control assembly. The partial-admission turbine includes a rotational assembly and a plurality of partial-admission turbine stages. The rotational assembly includes a bladed turbine rotor. The bladed turbine rotor includes a plurality of rotor blade stages. Each of the plurality of partial-admission turbine stages includes a respective rotor blade stage of the plurality of rotor blade stages. The fluid source, the first heat exchanger, and the partial-admission turbine sequentially form a portion of a fluid flow path through the assembly. The mechanical load is coupled to the rotational assembly. The control assembly including a controller configured to determine a corrected turbine inlet flow and a corrected rotation speed for the partial-admission turbine, maintain the corrected turbine inlet flow within an inlet corrected flow threshold range, and maintain the corrected rotation speed within a corrected rotation speed threshold range.