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The Lublin R-XIII was the Polish army cooperation plane (observation and liaison plane), designed in the early-1930s in the Plage i Laśkiewicz factory in Lublin. It was the main army cooperation plane in the Invasion of Poland. Its variant Lublin R-XIV was a military trainer aircraft. ==Design and development== In 1927, the Polish aviation authorities announced a contest for an army-cooperation plane (in Polish: ''samolot towarzyszący'', literally: "accompanying plane"). In Polish doctrine it was a close reconnaissance, observation and liaison aircraft, operating from casual airfields, providing big Army land units with information about the enemy. The PZL state factory proposed the PZL Ł-2, built in a series of 25 aircraft, while private factory Plage i Laśkiewicz in Lublin proposed the Lublin R-X, designed by Jerzy Rudlicki. It was flown on February 1, 1929. Five aircraft were built for the Air Force as R-Xa, and one was built as a long-distance sports plane. The third competitor was the PWS-5t2. The contest was won by the R-Xa, having the shortest take-off and landing, and good performance, but the factory was ordered to develop design further. At that time, Rudlicki was working upon an unarmed trainer aircraft R-XIV and an observation aircraft R-XV. Both were new designs, basing upon the R-X construction. Number XIII was initially omitted in designations as "unlucky". In February 1930, the Polish Air Force ordered 15 of R-XIV. The first serial plane was built in June 1930, without an earlier prototype, and all were delivered by July 1931. The R-XIV was a two-seater, parasol wing aircraft, with a 220 hp radial engine and fixed landing gear. The crewman sat in open cabs in tandem. The R-XV was not ordered, but the Air Force demanded instead, that two R-XIV should be armed with an observer's machine gun, for testing. Thus armed, the R-XIV, fitted also with other minor modifications, most notably a changed shape of a tail fin, became the first prototype of the army-cooperation plane, that received a designation Lublin R-XIII. On July 21, 1931, 50 aircraft R-XIII were ordered. The first series of 30 were designated R-XIIIA, the next 20 were R-XIIIB. Both variants differed mostly in a type of a machine gun ring mounting. The first serial R-XIII was built on June 7, 1932. By March 11, 1933, all were given to the Air Force. In 1932, next 170 aircraft were ordered. 48 were built in R-XIIIC variant with minor modifications, then 95 were built in a most numerous R-XIIID variant. It introduced visible changes, like a Townend ring on a radial engine, and a new engine cowling. It also had new type of a machine gun ring mounting. The first R-XIIID was tested in February, 1933. All aircraft were given to the Air Force by March 2, 1935. During repairs, older models A, B and C were modified to R-XIIID standard as well. In 1933, Jerzy Rudlicki proposed a new design R-XXI, for a new contest for R-XIII successor, but it was not accepted (the contest was won by the RWD-14 Czapla). However, some of R-XXI features, like higher and rounded in cross-section fuselage and changed shape of a tail fin, were found in latest R-XIII variants. Single prototype of the R-XIIIE was built in 1934, fitted with a stronger 360 hp engine Gnome-Rhone 7K Titan, but it was not produced. Another variant R-XIIIF introduced new, Polish-designed 340 hp engine Skoda G-1620A Mors-I. It had no Townend ring on cylinders of the radial engine. After one prototype (no. 56.101), a series of 50 R-XIIIF were ordered in 1934. After seven aircraft had been delivered, the Polish aviation authorities refused to buy nearly-completed further 18 aircraft, planning to nationalize all aviation industry in Poland. As a result, Plage i Laśkiewicz factory went bankrupt in late 1935, and it was next nationalized under a name LWS (''Lubelska Wytwórnia Samolotów'' - Lublin Aircraft Works). Then, 18 R-XIIIF, bought by scrap price, were completed, and next series of 32 was built. All R-XIIIF were delivered to the Air Force by 1938. However, only 26 of them were completed with Mors engines (and mostly used for training or staff liaison), while 32 had standard 220 hp Wright engines, lowering their performance to R-XIIID level. In 1931, one R-XIV was tested on floats, as a seaplane. Since tests came out well, the Polish Navy designated it R-XIII bis/hydro and ordered the next three (nos. 700-703). In 1933, the Navy ordered 10 R-XIII ter/hydro, which was a seaplane variant of R-XIIID (nos. 704-713). Finally, in 1934 the Navy bought 6 R-XIIIG seaplanes, differing in details from a previous variant - among others, a metal propeller (nos. 714-720). They were delivered by April 1935. All variants could also be easily converted to wheeled landing gear. In 1933, one R-XIIIB was converted to a long-distance sport plane R-XIIIDr, named ''Błękitny Ptak'' (the ''Blue Bird''), meant for a flight to Australia, however it was crashed in 1935 in Siam by Stanisław Karpiński. Several aircraft were converted to civilian sport ones, used in Polish Aero Clubs. 12 R-XIII's were converted to blind flying trainers R-XIIIt in 1934, with higher closed trainee cab. Some were converted to simple liaison aircraft, removig armament and mounting a windscreen in the second cab. Several R-XIII were used to tow gliders, using a special frame with a hook, attached to a fuselage. The R-XIII prototype was converted in 1932 to an experimental variant R-XIX, with V-tail of Rudlicki's design, but it was not accepted by the authorities, despite it had better field of machine gun fire. In total, 15 R-XIV and 273 R-XIII were built, including 20 seaplanes. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lublin R-XIII」の詳細全文を読む スポンサード リンク
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