US Patent 6868664 Main propulsion engine system integrated with secondary power unit

A main engine mounted auxiliary power unit comprises an auxiliary power unit integrated with a primary gas turbine engine into a single power plant suited for aircraft applications. The auxiliary power unit can be mounted within an engine core compartment of the main engine or at the main engine aft center body. The integration of the auxiliary power unit provides for installation and certification cost savings to the airframer by eliminating the need for mounting an auxiliary power unit to the tail section of the aircraft.