International aviation technology indicates that conventional aircrafts employing liftbody configuration achieved excellent results in lift enhancement. However, no canard-configuration fighters employed the liftbody design. This is not because no one recognized the advantage of the liftbody configuration but the result of canard placement on canard-configuration aircrafts. Canard-configuration fighter designs generally place the canards above the wings to allow the downwash generated by the canards to interact with the wings. This allows the aircraft to use the interaction of the vortices to produce beneficial couplings that will enhance the lift coefficient. It is difficult for liftbody configurations to satisfy this condition (liftbody design requires the canards to be level with the wings).
Pursuit for supersonic cruise drag characteristics forced the CAC to tinker with the canard liftbody configuration to open a new path in its pursuit for a Fifth gen. design.
CAC discovered during experiments that although adopting the lift body canard configuration reduces the lift contributions from the canards, its overall lift performance is better than that of a non lift body canard aircraft as long as the canards, LERX, and wings were placed at proper distances and angles with respect to one another. The designers were thrilled by this discovery
Further studies indicate that canard configuration aircrafts employing liftbody and LERX derive lift not only from the longitudinal coupling between the canards and forward portion of the LERX with the wings’ shed vortices but also the benign interferences between left and right shed vortices. The latter adds significant lift to the aircraft and greatly contributes to the improvement of lift characteristics.
Even more encouragingly, aircrafts employing the liftbody LERX canard configuration could select smaller aspect ratios. This will, without a doubt, reduce pressure on engine performance. The CAC discovered after numerous experiments that candard configuration planes employing liftbody LERX could, under high AOA conditions, concentrate the lift on the plane's body and inner portions of the wings. After properly reducing the wings’ aspect ratio the highest lift coefficient actually increased instead of decreasing as predicted. This is an amazing phenomenon.
Under conventional aerodynamic configuration, supersonic drag, maximum lift under low speed, and transonic lift to drag ratio suffer from contradictory design requirements. Aircraft wing designs have the most significant effect on supersonic drag. Wings with mall aspect ratio and large sweep angles offer lower drag at supersonic speeds but are detrimental to the other two requirements. The Mig-21 is a good example of this since its wings, with a sweep angle of 57 degrees and an aspect ratio of 2.22, offers very good supersonic performance but worse performances at lower speed.
Under a lift body LERX canard configuration, however, these two traditional contradictions of aerodynamic design became, to a certain degree, reconcilable! The new discover of using liftbody LERX canard configuration allows the aircraft to select smaller aspect ratios than its conventional counterpart (very beneficial for raising the design threshold for low speed characteristics) while maintaining better low speed characteristics than conventional configuration aircrafts. This major discovery allow nations that are comparatively backwards in engine technology to use their available technology to build low cost Fifth gen. aircrafts while maintaining the said aircrafts’ supersonic and low speed high AOA capabilities.
The discovery CAC made in flight aerodynamics resulted not only in a firm technical base on which China's Fifth generation fighter project can build upon but also greatly contributed to the world wide aeronautic industry. This marks the first time that the Chinese aerospace industry moved from being a imitator of aerospace technology to an innovator and pioneer.