Available thrust

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

• a rich burn, quick quench, lean burn (RQL) combustor having a number of fuel spray nozzles in the range of 14-22 or a number of fuel spray nozzles per unit engine core size in the range 2 to 6;
• and
• wherein:
• a thrust nvPM emissions index ratio is defined as:
• EI
• maxTO
• /
• F
• maxTO
• EI
• idle
• /
• F
• idle
• where:
• EIidle is the nvPM emissions index in mg/kg of the gas turbine engine if operating at around 7% available thrust for given operating conditions;
• EImaxTO is the nvPM emissions index in mg/kg of the gas turbine engine if operating at around 100% available thrust for the given operating conditions;
• FmaxTO is the thrust of the gas turbine engine at around 100% available thrust in kN,
• Fidle is the thrust of the gas turbine engine at around 7% available thrust in kN;
• the thrust nvPM emissions index ratio is greater than 0.09;
• and
• the gas turbine engine is configured to provide fuel comprising a sustainable aviation fuel (SAF) to the fuel spray nozzles;
• wherein the method comprises providing fuel comprising a sustainable aviation fuel to the fuel spray nozzles.