LWS-6 Żubr

LWS-6 Żubr
PZL.30 Żubr
Role	Medium bomber
Manufacturer	LWS
First flight	March 1936
Introduction	1938
Retired	1940s
Primary user	Polish Air Force
Produced	1938
Number built	17

The LWS-6 Żubr (PZL.30 Żubr, wisent) was a Polish twin-engined medium bomber, produced by the LWS factory before World War II. A short series was used for training only, because it was inferior to the PZL.37 Łoś design.

It was designed by PZL in the early 1930s, initially as a passenger aircraft (the main designer was Zbysław Ciołkosz). Since the Polish Airlines LOT bought Douglas DC-2 planes instead, the project was converted to a bomber aircraft, with a projected bomb load of 1,200 kg. It was developed as an alternative less-advanced design, in case the modern bomber design, PZL.37 Łoś would fail. The first prototype, designated PZL.30 (or PZL.30BI) was flown in March 1936 by Bolesław Orliński (only three months before the PZL.37 prototype).

The prototype, initially powered with two 420 hp Pratt & Whitney Wasp Junior engines, was next refitted with much stronger 700 hp Bristol Pegasus VIII (it was known then as PZL.30BII). The plane was accepted for a limited production by the LWS state factory in Lublin, of which Ciołkosz became the main designer. It was planned to produce 16 aircraft for the Polish Air Force, under a designation LWS-6 Żubr. The serial aircraft incorporated further changes, among others a landing gear folding into a fuselage sides was changed to more conventional one folding into engine nacelles. After a prototype crash on November 7, 1936, caused by a weak construction of a wing, the design had to be strengthened. Due to this increased weight it had a smaller bomb load than expected. An improved prototype was made with a double tail fin, and flown at the end of 1937. The serial variant, however, returned to a single tail fin configuration, but it was enlarged in a course of production. A series of 15 aircraft were built in 1938. The factory continued work on Żubr development, and in 1939 developed a lighter wing of steel construction and a refined fuselage, but these were not built due to the outbreak of World War II.

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