PZL.4

The PZL.4 was a Polish three-engine passenger aircraft for 10 passengers, built in PZL factory in 1932, which remained a prototype. It was the first Polish-designed and produced multi-engine plane.

==Development== Despite purchasing a number of three-engine Fokker F.VIIb/3m aircraft, LOT Polish Airlines soon started looking for a more modern design and organized a design contest in 1928. The contest was won by the Polish engineer Zygmunt Bruner, working in the French Bernard works, with his design T-600. It was an all-metal high-wing three-engine monoplane, similar to Ford Trimotor. State Aviation Works PZL decided to take over its development, and a group of engineers was sent to Paris and worked the design in 1929, under direction of Zygmunt Bruner. There were also carried out aerodynamic trials of a plane model. Detailed technical drawings were worked in PZL in Warsaw in 1930, under direction of Stanisław Prauss, and a prototype was built, designated PZL.4 (this designation was used before for a single-engine design worked out for a passenger plane contest in 1928, won by PWS-20).