Flow guidance device for cooling the low pressure turbine casing of a gas turbine engine

The gas turbine jet engine has a housing structure (22) radially surrounding the main flow channel (20), in which a housing gas flow flows in a same direction as a main flow in the main flow channel. The housing structure has an adjustable flow conducting assembly (25), which adjusts the flow of the housing gas flow to or along the main flow channel. The flow conducting assembly has flow conducting sheet (26) dividing the housing gas flow into two partial flows, one partial flow running near the main flow channel and another partial flow running at a distance from the main flow channel.