The P.W.S.12 was a Polish intermediate trainer that entered production in 1931, but that was completed as the improved P.W.S.14.
The original version of the P.W.S.12 was related to the P.W.S.11 parasol wing trainer of 1927, which was designed to go with the P.W.S.10 parasol wing fighter. The P.W.S.11 never entered production, as the P.W.S.10 was only ever seen as an intermediate design, and after a brief period of front line service was replaced by the P.Z.L. P.7 and was used as a trainer itself.
The first design of the P.W.S.12, produced late in 1927, used the fuselage, undercarriage and wing from the P.W.S.11, with a shorter lower wing added to turn it into a biplane, and was to be powered by a 240hp Gnome-Rhone Titan five-cylinder radial engine. The fuselage was built with a wooden structure. In 1928 the design was altered to use a 220hp Skoda built Wright J.5 Whirlwind radial engine, and the wingspan was reduced.
In 1929 the design was changed again. It was now given staggered wings, the original rectangular cross section of the fuselage was covered with fairings to give it an oval cross-section and the engine was given a Townend ring. P.W.S. was given an official contract to produce a prototype and a structural test airframe in the spring of 1929, followed later in the year by a contract for a second prototype.
The static tests were carried out on 22-23 October 1929, and the first prototype made its maiden flight in November 1929. The first prototype was then modified to take into account the results of its manufacturer’s trials, and was given rounded wingtips, a smaller Townend ring and a number of minor changes. Trials with the modified prototype began in the spring of 1930. It was then given new N shaped interwing struts, before going for its official trials.
The second prototype (the P.W.S.12bis) was modified to take into account recommendations from the official trials. The wing area was increased, the wingtips were made more rounded and it was given a Ratier two-blade adjustable pitch metal airscrew. The wingspan and length both slightly increased, as did its weight. During official trials over the winter of 1930-31 it was recorded as having slightly better performance than the original prototype.
The P.W.S.12bis made a public appearance in March 1931, flying to Riga and Tallinn to mark the formation of the Estonian Air League.
In 1930 P.W.S. began work on an improved version of the design, which replaced the wooden fuselage structure with welded steel tubes. This became the P.W.S.14. Early in 1931 the Polish Department of Aeronautics ordered twenty P.W.S.12 trainers, made an advanced payment for this first batch and indicated that they would probably order more. However later in the year they changed their mind, and decided to replace the order for the P.W.S.12 with an order for the P.W.S.14. By this point work had already begun on the first twenty aircraft, so they had to be modified to use the new fuselage, as well as introducing other changes that were also seen on the SP-AKE civil aircraft of 1933.
This change delayed their delivery until 1932. At first they actually carried the P.W.S.12 designation on their tails but this was changed once all of the contracts were modified. This batch of twenty aircraft were the only ones to be completed as the P.W.S.14 before further orders were changed to be for the more advanced P.W.S.16.
In 1933 a modified version of the P.W.S.12bis appeared. This was probably produced by modifying the second prototype, and had the P.W.S. serial number 358 and the civil registration SP-AKE. This version was designed for aerobatics and inverted flying. It had new a rounded rudder and elevator, an extended Townend ring, used a Ratier airscrew and has a streamlined gravity fuel tank carried between the undercarriage legs to provide fuel when inverted. In April 1933 this aircraft appeared at the Bulgarian Air Display in Sofia, where it provided a impressive 55 minute display of aerobatics. SP-AKE had similar dimensions to the P.W.S.14.
First Prototype during Official Trials of 1930
Engine: Polish Skoda Works (Wright) J.5 Whirlwind nine-cylinder radial air-cooled engine
Span: 28ft 2.75ft
Length: 21ft 9.75ft
Height: 9ft 2.25in
Loaded Weight: 2,337lb
Maximum Speed: 110mph at sea level, 101.9mph at 6,561ft
Climb rate: 3,280ft in 4min 15sec