The turbo-fan engine of this invention is typical of high bypass ratio turbo-fan engines in that it is constructed with a circumferential bypass duct defined by outer and inner shrouded frames to which the core engine is fixed. Incoming air is pressurized by a fan mounted at the engine inlet. Downstream of the fan, the pressurized air is divided between a transition passage which supplies air to the compressor section of the core and the bypass duct which provides air for propulsive thrust. Compressed air from the compressor passes through a diffuser and is supplied to a combustor. Fuel is added in the combustor and the pressurized gas drives a high pressure turbine. The high pressure turbine powers the compressor.