Lublin R-X  The Lublin R-X was a Polish single-engined, two seat liaison aircraft, built in 1929 in the Plage i Laśkiewicz factory in Lublin. Seven were completed, two of them prototypes. Four served with Polish air regiments and another made several notable long flights and tours. In 1927, the Polish War Ministry opened a contest for a military liaison and observation plane for use by Army land units operating from casual airfields. The private factory Plage i Laśkiewicz in Lublin proposed the Lublin R-X, designed in 1928 by Jerzy Rudlicki. Fitted with skis, the prototype was first flown, off snow, on 8 February 1929, followed by a second prototype in the spring. They were extensively tested and handled very well. During these tests, both prototypes became the first Polish aircraft to be fitted with Townend rings around their normally uncowled radial engines. Five pre-series aircraft followed 1929, the first four differing from the prototypes in having a detachable ring mounting for a Lewis gun in the rear cockpit. The fifth, designated the R-Xa, was built as a strengthened, unarmed, long-distance tourer with a modified exhaust system and a fuel capacity of that gave it an endurance of 18 hours. The R-X was a braced parasol wing design of mixed construction (steel and wood) and conventional in layout. Its wing was built in two parts based on two wooden spars, with plywood around the leading edge and fabric covered elsewhere. In plan the wing was rectangular centrally, with semi-elliptical tips. It was braced by a pair of parallel steel struts to the lower fuselage and held over the fuselage by an inverted-V cabane. Structurally its fuselage was a rectangular section frame formed with welded steel tubes. The forward part was covered with duralumin sheet and the rest with fabric. It was powered by a Wright Whirlwind J-5Ab, an air-cooled, nine-cylinder radial engine licence built in Poland by Skoda. This was usually uncowled, though Townend rings were fitted to some examples from time to time. Both wood and metal propellers of diameter were used. There was a droppable fuel tank in the forward fuselage. The R-X had two open cockpits in tandem, fitted with dual controls; the rear cockpit had a gun-mounting ring. Its empennage was conventional and structurally similar to the fuselage, with steel tube frames and fabric covering.