Flat-turn maneuver, which means turning without banking, is a useful method for ground observations. Former studies suggest fixed-wing small unmanned aerial vehicles equipped with side-force plate (SFP) to improve turning performance. However, the turning performance of flat turn is usually much inferior compared to conventional banked turn. This paper presents an aircraft design suited for flat turn by showing indoor flight test results. In order to turn in a high rate, the aircraft should turn by skidding. In addition, the SFP should be located fore of the center of gravity as a vertical canard. Furthermore, the main wing should be designed not to generate rolling moments when turning. The results of the flight tests reveal that applying both rudder and SFP is very effective in turning the aircraft in a high rate without banking.