Electric enhanced transmission for multi-spool load-sharing turbofan engine

A method of proportioning a load between spools of a turbofan engine comprising:

• coupling an intermediate gear of a superposition gearbox to a first spool including a first turbine, wherein the superposition gearbox comprises a sun gear, a plurality of intermediate gears engaged to the sun gear and supported within a carrier fixed to a static structure and a ring gear circumscribing the plurality of the intermediate gears;
• coupling a first portion of an integrated motor/generator to a second spool including a second turbine, the integrated motor/generator comprising an inner motor/generator and an outer motor/generator;
• coupling a second portion of the integrated motor generator to the superposition gearbox;
• coupling the sun gear to an electric motor;
• controlling a speed of the sun gear with the electric motor;
• and
• controlling a stator field of the integrated motor generator to proportion a load between the first spool and the second spool;
• wherein a first tower shaft is engaged to the first spool and a second tower shaft is engaged to the second spool;
• wherein one of the first tower shaft or the second tower shaft drives one of the intermediate gears and wherein the first tower shaft is concentric with the sun gear;
• wherein the inner motor/generator comprises an inner armature and a stator disposed radially outside of the inner armature, wherein the ring gear is coupled to drive the inner armature;
• and
• wherein the outer motor/generator comprises an outer armature disposed radially outside the stator, wherein a first load on the first spool and a second load on the second spool is adjusted by operation of at least one of the inner motor/generator and the outer motor/generator.