GAS TURBINE ENGINE SYSTEM

A gas turbine engine system 100 comprises a hydrogen-burning gas turbine engine and a fuel system comprising (i) a fuel line 114 arranged to receive gaseous hydrogen at an input 115 thereof and provide the gaseous hydrogen to combustion apparatus 106 of the hydrogen-burning gas turbine engine and (ii) a vent line 116 including a vent valve 104 and having a first end coupled to the fuel line and a second end disposed remotely from the hydrogen-burning gas turbine engine. A controller 112 is arranged to switch the vent valve from a closed state to an open state upon detection of an engine shaft-break or similar condition, thus providing rapid evacuation of gaseous hydrogen from the fuel line and hence rapid shut-down of the engine. The engine may be shut down more rapidly than is possible by means of a shut-off valve within the fuel line.