GAS TURBINE ENGINE WITH THIRD STREAM

A gas turbine engine defining a centerline and a circumferential direction, the gas turbine engine including: a turbomachine comprising a compressor section, a combustion section, and a turbine section arranged in serial flow order, the turbomachine defining a working gas flowpath and a fan duct flowpath; a primary fan driven by the turbomachine defining a primary fan tip radius R1 and a primary fan hub radius R2; a secondary fan located downstream of the primary fan and driven by the turbomachine, at least a portion of an airflow from the primary fan configured to bypass the secondary fan, the secondary fan defining a secondary fan tip radius R3 and a secondary fan hub radius R4, wherein the secondary fan is configured to provide a fan duct airflow through the fan duct flowpath during operation to generate a fan duct thrust, wherein the fan duct thrust is equal to %Fn3S of a total engine thrust during operation of the gas turbine engine at a rated speed during standard day operating conditions; wherein a ratio of R1 to R3 equals EFP1−RqRSec.−Fan21−RqRPrim.−Fan21%Fn3s−1; wherein EFP is between 1.5 and 11, wherein RqRPrim.-Fan is a ratio of R1 to R2, and wherein RqRSec.-Fan is a ratio of R3 to R4.