The four engined Upper Surface Blowing (USB) STOL research aircraft ASKA was developed by National Aerospace Laboratory of Japan and has been in the flight test phase to provide various kinds of flight data.The position error in airspeed and angle of attack is discussed, and the low speed performance demonstrated in the flight test is provided by the figures of lift/drag coefficient curves and V-Gamma plot. Several indications of powered lift and dynamic stability derivatives obtained from the V-Gamma plot are discussed. The flight measured pitching moment shows the distinctive features such as pitch up tendency. The wing-body pitching moment and the downwash angle are analyzed from the flight load measurments of the horizontal tail. The ground effect of the ASKA is also presented quantitatively in this paper.THE QUIET SHORT TAKE-OFF AND LANDING (STOL) capability is very beneficial for the Japanese domestic aviation, since airports have short runways in the vicinity of the residential area in Japan.The National Aerospace Laboratory (NAL) developed the experimental aircraft ASKA to make a flight research on the quiet upper surface blowing (USB) STOL technology (1)*. The ASKA is a conversion of the Kawasaki C-1 tactical transport installed with four newly developed FJR710/600S turbofan jet engines.The ASKA made the first flight in October 1985, and the flight verifications on the basic aircraft systems and performance had been made first in a step by step manner from shallower to deeper flap angle. The basic airworthiness flight test including the Stability and Control Augmentation system (SCAS) was finalized by the actual STOL configuration landing, and the intensive evaluation of the STOL landing configuration follows that.Various kinds of the flight test have been made (2), (3) and (4), however, the key issues of the USB STOL technology are low speed capability. In this paper, the position error in airspeed and angle of attack is discussed first and the low speed and powered lift characteristics of the landing configuration of the ASKA were presented. The lift and drag performance was surveyed and the airspeed and flight path angle plot, namely V-Gamma plot, was derived from the lift and drag curves. Several indications for the powered lift and dynamic stability derivatives were obtained from the V-Gamma plot.The distinctive pitching moment performance was analyzed by decomposing the wing-body and horizontal tail components with using the tail load measurement system.The ground effect was also analyzed to give quantitative information to achieve the precision point touchdown of the aircraft.The discussions in this paper are based on the newest flight data until the fall of 1988, and are the current status report of the flight test of the ASKA.