of those components and their operation is incorporated by reference here the axial compressor 122 is mounted between the core airflow passage 26 and the inducer sections 66 the axial compressor 122 includes an axial compressor rotor 146 from which a plurality of compressor blades 152 extend radially outwardly and a fixed compressor case 150 a plurality of compressor vanes 154 extend radially inwardly from the compressor case 150 between stages of the compressor blades 152 the compressor blades 152 and compressor vanes 154 are arranged circumferentially about the axial compressor rotor 146 in stages two stages of compressor blades 152 and compressor vanes 154 are shown in this example the axial compressor rotor 146 may be driven by the fan turbine rotor assembly 24 either directly or via a gearbox assembly 190 as shown the gearbox assembly 190 shown provides a speed increase between the fan turbine rotor assembly 24 and the axial compressor 122 at a ratio of 3 34 to 1 for example the gearbox assembly 190 may include a planetary gearset including a sun gear 192 coupled to the axial compressor rotor 146 and a planet carrier 194 coupled to the fan turbine rotor assembly 24 to provide a speed differential therebetween a plurality of planet gears 193 one shown are mounted to the planet carrier 194 the planet gears 193 engage the sun gear 192 and a ring gear 195 rotating the axial compressor rotor 146 at a rate higher than that of the fan turbine rotor assembly 24 increases the compression provided by the axial compressor 122 the gearbox assembly 190 could alternatively provide a speed decrease between the fan turbine rotor assembly 24 and the axial compressor rotor 146.