The Bü 133 was a development of the Bücker Bü 131 Jungmann two-seat basic trainer. First flown in 1935 (by Luise Hoffmann, the first female works pilot in Germany),[1] it was slightly smaller than the Bü 131. The prototype, D-EVEO, was powered by a 140 hp (104 kW) Hirth HM506 inverted, air-cooled inline-6 engine.[1]