Letov Š-20J is a modernized variant of the Š-20 aircraft from 1927 equipped with a star engine Walter Jupiter IV. The prototype had a better climb and speed compared to the serial aircraft Š-20, but the design of the fuselage of the Š-20 did not suit the new engine and the aircraft suffered from strong vibrations. Findings from prototype tests were later used in the construction of the Letov Š-31 aircraft.
Source:
www.wiki.modelforum.cz
Source:
www.wiki.modelforum.cz