Operating an aircraft

Abstract

A gas turbine engine 10 for an aircraft comprising a rich burn quick quench, lean burn (RQL) combustor 16 having a number of spray nozzles 403, 404, in the range of 14-22 or a number of fuel spray nozzles per unit engine core size in the range of 2-6, with the engine configured to provide fuel comprising sustainable aviation fuel to the spray nozzles. The engine operation is characterised by specific non-volatile particulate emission ratio beign related to the bypass ratio. The fuel spray nozzles may comprise one or more duplex nozzles and one more single flow nozzles and preferably the combustor comprises 10-14 duplex fuel spray nozzles and 4-8 signle flow fuel spray nozzles. The duplex fuel spray nozzles are arranged in groups about the circumference of the combustor and optionally wherein the groups duplex fuel spray nozzles comprise at least two groups arraned dimametrically opposite each other. A corresponding method is also claimed. Fig 6