or variable is a minimum area in the exhaust nozzle 68 a mechanically fixed throat area a8 provides weight and cost savings and benefits due to the fewer mechanical parts used and a lesser amount of mechanical complexity required of such a design a more particular embodiment of the present invention is illustrated in fig4 which shows the fan sections of the engine 10 and the gas generator 3 which is a core engine 18 the core engine 18 includes a high pressure compressor 20 the rich fuel burning combustor 22 and a high pressure turbine hpt 23 having a row of high pressure turbine hpt blades 24 all arranged in a serial axial flow relationship high pressure compressor blades 64 of the high pressure compressor 20 are fixedly interconnected in driving engagement to the high pressure turbine blades 24 by a larger diameter annular core engine shaft 26 which is disposed coaxially about the centerline 12 of the engine 10 forming a high pressure spool the core engine 18 together with the fuel rich burning combustor 22 is effective for generating relatively cool fuel rich combustion gases as explained above pressurized air from the high pressure compressor 20 is.