Rotary assembly

A gas turbine engine assembly, the assembly comprising:

• a gas turbine engine having a spool;
• and
• a rotary assembly of a pressurized air system for an aircraft, the rotary assembly comprising:
• a rotor mechanically coupled to the spool of the gas turbine engine,
• a flow modifier comprising a first section, defining a plurality of first flow channels configured to receive flow from the rotor, and a second section, defining a plurality of second flow channels configured to direct flow towards the rotor;
• wherein the rotary assembly is configured to permit relative movement between the rotor and the flow modifier to move between:
• a turbine configuration in which the rotor is configured to receive air from an external air source via the second flow channels to drive the spool to rotate;
• and
• a compressor configuration in which the rotor is configured to be driven to rotate by the spool and to receive and compress air from the gas turbine engine, and discharge the compressed air for supply via the first flow channels to an airframe system,
• wherein the second flow channels are angled and/or shaped such that a flow through at least part of the second flow channels is in a direction with a component in an axial direction of the rotor.