Fuel management system

A method of operating a gas turbine engine, the gas turbine engine comprising:

• an engine core comprising a combustor configured to burn a fuel;
• a turbine, the turbine comprising a plurality of turbine blades;
• a compressor configured to be used as a source of cooling air for the turbine blades;
• and an inducer configured to accelerate and direct the cooling air onto the turbine blades, the inducer comprising a plurality of airflow passageways and a modulating valve configured to control cooling air flow into a subset of the passageways;
• and
• a fuel management system comprising two fuel-oil heat exchangers through which oil and the fuel flow, the fuel-oil heat exchangers configured to transfer heat between the oil and the fuel and comprising a primary fuel-oil heat exchanger and a secondary fuel-oil heat exchanger;
• wherein the method comprises:
• using the fuel management system to provide a fuel with a sulphur content of less than 30 ppm to the combustor;
• and
• controlling the modulating valve to adjust the cooling air flow based on turbine inlet temperature, wherein
• for fuel that passes through both fuel-oil heat exchangers, a ratio of heat transfer from the oil to the fuel for the primary and secondary fuel-oil heat exchangers is between 70:30 and 90:10, and
• the fuel comprises sustainable aviation fuel, and the fuel is up to and including 100% sustainable aviation fuel.