Evaluation of a new jet flap propulsive-lift system for turbofan-powered STOL transports

A large-scale STOL transport model with a new jet flap propulsive-lift system was subject to wind-tunnel testing. Aerodynamically, this IBF system combines the benefits of the jet flap and the mechanical flap with boundary layer control. Structurally, it creates its own spanwise air duct with the deflection of the mechanical flap. An additional short-chord control flap, located at the jet-flap exit, provides a powerful means for flight path and lateral controls. The results show that the overall effectiveness of this flap system compares well with other jet flap propulsive-lift systems. A preliminary study based on the wind-tunnel data was made on a medium-size IBF STOL jet transport configuration for a typical-military mission. This study showed that the IBF results in a configuration with a relatively low T/W ratio, making the system an attractive candidate for future designs.