Patent ID: 7887287

Claim:
A turbofan jet engine, comprising: a core engine that generates a propulsive force by ejecting exhaust gas rearward; and a fan that generates a propulsive force by pushing an air flow rearward, and suppresses a noise of an exhaust jet of the core engine, wherein the fan comprises a front fan disposed in the vicinity or upstream of a compressor of the core engine, a front fan duct accommodating the front fan, an aft fan disposed in the vicinity or downstream of a turbine thereof, and an aft fan duct accommodating the aft fan, at least either one of the front fan duct and the aft fan duct is rotatable, and an area of overlap between an outlet of the front fan duct and an inlet of the aft fan duct changes in accordance with the rotation of the front fan duct or the aft fan duct, whereby a bypass ratio of the engine changes.