A gas turbine engine having an engine core defining a core flow path delimited by an engine casing, a washing device having a spraying member defining a conduit in fluid communication with a source of washing fluid, the spraying member having a spraying section for outputting the washing fluid from the conduit, the spraying member movable relative to the engine casing from a retracted position in which the spraying section is flush with a surface of the engine casing defining said core flow path, and an expanded position in which the spraying section protrudes beyond the surface of the engine casing into the core flow path