Fuel supply system

A fuel supply system for fuel injectors of a multi-stage combustor of a gas turbine engine, the fuel supply system including:

• a metering and splitting arrangement which receives a total fuel flow and controllably meters and splits the received total fuel flow into metered pilot and mains flows for injecting respectively at pilot and mains fuel discharge orifices of the injectors to perform staging control of the combustor;
• and
• pilot and mains fuel distribution pipeworks respectively distributing fuel from the metering and splitting arrangement to the pilot and mains discharge orifices;
• wherein the metering and splitting arrangement is operable to select the pilot distribution pipework and deselect the mains distribution pipework for pilot-only operation in which there is a pilot supply to the combustor but no mains supply to the combustor from the injectors, and is operable to select both the pilot and mains distribution pipeworks for pilot and mains operation in which there are pilot and mains supplies to the combustor from the injectors;
• wherein fuel supply system further includes a de-priming sub-system, one or more fuel lines of the mains fuel distribution pipework being fluidly connected to the mains fuel discharge orifices and extending to the de-priming sub-system, and the de-priming sub-system being configured to remove the mains fuel from the injectors through the one or more fuel lines when the mains distribution pipework is deselected for pilot-only operation;
• wherein the fuel supply system further includes a re-priming sub-system, the one or more fuel lines of the mains fuel distribution pipework also extending to the re-priming sub-system, and the re-priming sub-system being configured to refill the injectors with mains fuel through the one or more fuel lines when the mains distribution pipework is selected for pilot and mains operation;
• and
• wherein the de-priming sub-system includes one or more sinks in which the removed fuel is stored, the re-priming sub-system emptying the sink(s) to perform refilling using the stored fuel.