In the mid-tandem fan concept, a high specific flow single stage fan is located between the high pressure (HP) and low pressure (LP) compressors of a turbojet core. Only bypass air passes through the fan. The LP compressor exit flow passes through passages within the fan disc, directly underneath the fan blades. Some bypass air enters the engine via an auxiliary intake. During take-off and approach the engine behaves much like a conventional turbofan, with an acceptable jet noise level (i.e., low specific thrust). However, for supersonic cruise, the fan variable inlet guide vanes and auxiliary intake close to minimize bypass flow and increase specific thrust. In this mode the engine acts more like a 'leaky' turbojet (e.g. the F404).