PZL P.24 A-G


To what extent did Pulawski's concept influence the development of airplanes around the world? Although his fighter design was state-of-the-art, its heyday was brief. Advances during the 1930s were so rapid that by 1936 cantilevered mid-wing designs with retractable landing gear were the design of the future. Pulawski's arrangement was used in only 730 high wing fighter planes, but close to 4,000 biplane fighters and almost 1,500 flying boats were built with gull wings. It can be safely stated that Pulawski influenced the construction of at least 6,000 airplanes and 2,000 gliders.

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Pulawski's fighter planes with in-line engines
As a result of an initiative in 1928 from the head of the Department of Aeronautics in the Ministry of Army Affairs, Col. Ludomil Rayski, the newly opened PZL factory cut its teeth on a production license for the French Wibault 7 fighter plane. (Designer and engineer Michel Wibault would, 30 years later, outline a concept for vectoring thrust by means of nozzles, which evolved into the Pegasus engine powering the first successful VTOL plane, the Harrier). The Wibault 7's construction was innovative with a 0.4-0.5 mm duralumin skin strengthened with corrugations placed at regular intervals. In addition to this, Wibault, came up with the idea of using over-sized flat ribs in the wings with "shelves" for the skin to be riveted to the ribs instead of riveting the skin to the folded edge of each wing rib (which made for difficult riveting). This made it possible to rivet from the outside with easy access to the rivets. Pulawski used the idea in his own design with some improvements. He increased the number of corrugations in the plates and eliminated the raised ribs on the wing upper surfaces and control surfaces without compromising ease of riveting.
Pulawski incorporated the following ideas into his first fighter design: gull wings, Wibault's wing and control surface ribbing, a "scissors" undercarriage and a 600hp in-line engine that allowed for an aerodynamically refined fuselage design and better visibility than a radial equivalent. The PZL design office was so busy in the first half of 1928 getting the Wibault 7 ready for production that the documentation for the PZL P.1 was drawn up in the second half of the year. Together with the start of production of the Wibault 7, at the beginning of 1929 the workshop began construction on the first prototype of the PZL P.1. The tempo was fast, with the first machine being ready for test flying in August 1929. The first test flight was made by Boleslaw Orlinski, a well-known aerobatics pilot (225 loops during one flight) and experienced in long distance flying (22,600 km [14,043mi.] Warsaw – Tokyo – Warsaw in 1926). That first flight was dramatic and would decide the further fate of Pulawski's fighter plane. In order to reduce the weight of the plane the decision was made to use a new material, magnesium alloy, on all the wing and aileron leading edges. The alloy is lighter than duralumin but more brittle. When Orlinski had reached a sufficient altitude to test the plane's dive speed a section of the leading edge on the starboard wing crumpled, forming a flat surface much wider than the wing's thickness, which acted as a brake. As a result the wing lost a lot of lift and the damage-induced drag caused the aircraft to tilt and turn to starboard. The plane became very difficult to control and Orlinski would have been justified in using his parachute, but he was aware that such a catastrophe with the prototype would end all chances of further development on the plane. Fighting for control, Orlinski carefully nursed the plane back to Mokotow airfield and thus saved the prototype. The leading edges were replaced with duralumin and on September 25 Orlinski made a successful test flight. He climbed to an altitude of 2,620 m (8,595 ft.) in 3 minutes and 40 seconds for a climb rate of 11.9 m/sec. (2,340 ft/min) and attained a maximum speed of 295 km/h (183 mph) which at the time were excellent results for a fighter plane. A competing plane made at the time, the PWS-10, had a climb rate of 6 m/sec. (1,176 ft./min.) and a top speed of 241 km/h (149 mph). The first trials, however, indicated a need for some improvements. A second prototype was built in 1930 with modified vertical stabilizers and an elevator without aerodynamic compensation. Orlinski test flew the PZL P.1/II at the end of March, 1930, and in June Col. Jerzy Kossowski took the PZL P.1/II to the International Fighter Competition held in Bucharest, Romania. Although his bid was successful, Romania later abandoned its intention to purchase a fighter as a result of the country's weak economy. The competition in Bucharest was Pulawski's first international show, and his first success, but didn't insure the production of his fighter. The Polish authorities had decided that their air force would not utilize in-line engines, and that such engines would not be built in Poland.

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