The aircraft was developed for a contest for an airliner for LOT Polish Airlines, announced by the Polish Ministry of Communication in 1927. The bestdesign was PWS-20, developed by Zbysław Ciołkosz. A prototype was built and flown on 12 March 1929 in Biała Podlaska. It was next bought by the Ministry of Communication for evaluation. In 1930 the plane was modified, with wider landing gear base and improved engine's cooling and exhaust systems and passenger cabin. After modifications it was designated PWS-20bis and received markings SP-AAZ. In 1930 the second prototype of PWS-20bis was built for the same user. Both aircraft were tested in 1929-1931 in domestic lines of LOT, mostly for goods' transport. In a meantime however, LOT bought a party of single-engine Fokker F.VIIa/1m aircraft abroad. Performance and flight characteristics of PWS-20 were evaluated as similar to Fokker, but it was worse comparing economy of service and maintenance needs. Therefore, in 1933 one aircraft was withdrawn from use in Poznań, while the second was written off in Warsaw. There started a construction of the third aircraft, but it was not completed. There were some plans to complete it for a flight around the world, but they were abandoned due to financial problems. Also the designer planned a floatplane variant PWS-20ter for communication with Denmark and Sweden, but it was not realized.
Description (PWS-20bis)
High-wing braced monoplane of mixed construction, with closed cab and single engine. A fuselage made of duralumin and steel frame, covered with canvas and duralumin in engine section. Wooden wing, with rounded endings, two-spar, plywood covered. Wooden tailfins, canvas covered. Crew of two, in a cab before the wing, with twin controls. Next and slightly below in a fuselage, under the wing, there was a cabin for 6 passengers, with wide rectangular windows and door on the left side. Two more passengers could be carried on folding seats. The cabin had a toilet and places for 170+50 kg baggage. W12 engine Lorraine-Dietrich LD 12Eb in the fuselage front. Radiator Lamblin under a fuselage. Two-blade metal propeller of a fixed pitch. Conventional fixed landing gear, with a rear skid. Fuel tanks 600 l in central wing section.
