Designers Pavel Benes and Miroslav Hajn made their debut with the BH-1 Experimental monoplane. In 1920. it was awarded at the aviation exhibition in Prague. The further development of this design led to the creation of the BH-1bis aircraft, and later the Avia BH-3 fighter. The first flight of the prototype took place in 1921. It showed good flight properties and after introducing a few corrections on June 16, 1921. was presented to representatives of military aviation. The wing structure was damaged during the flight. The flying pilot Munzar was killed. The army, however, did not give up on the purchase of the plane, especially since the presentation of the second prototype went smoothly. Of the 10 serial Avii ordered, the first went to the squadrons in August 1923. This type of aircraft had a disastrous reputation for flight instability and a tendency to spin. As a result, they quickly disappeared from linear units. For some time they were used for training at the flight school in Cheb. The Avia BH-4 was a further development of this design. Construction: completely wooden, single-engine, single-seat, low-wing low wing. Classic, two-wheeled, fixed undercarriage. The drive was a BMW III in-line engine with 136 kW (185 hp). Armament: 2 synchronized 7.7mm Vickers MGs located above the engine. Other technical data: Maximum speed: 240 km / h, speed of climb: 7.9 m / s, maximum ceiling 7800 m, maximum range: 500 km.