J.Zynk Polish Aircraft 1893-1939 (Putnam)

Aquila Monoplane

   In 1909 the brothers Rudolf and Wincenty Schindler of Krakow evolved a study for a multi-seat tractor high-wing monoplane of very advanced concept. At the end of October of that year a flying scale-model of the proposed aircraft, powered by a rubber-cord driven airscrew, was displayed by the brothers in the Technicians' House in Krakow. The model, which aroused considerable interest, made a successful flight inside the exhibition hall, taking-off from the floor under its own power. The Schindler brothers came into contact with Henryk Brzeski, the Polish engine inventor working in Vienna, who agreed to help them with the development of the machine and to design a powerplant for it. Early in 1910 the project, which became known subsequently as the Aquila, was revised by the Schindler brothers and Brzeski working together, the changes introduced including the replacement of the normal control method and tail unit by an unconventional control system which dispensed with the vertical tail surfaces. Construction of the aircraft began in Vienna.
   Henryk Brzeski was the creator of a reaction-free bi-rotary engine, in which the cylinders and crankcase rotated one way and the crankshaft the other. The first of his experimental engines built on this principle appeared in 1907 and soon the rights to a number of his engine patents and designs were purchased by Gnome and Siemens and later also by Daimler. For the Aquila monoplane Brzeski evolved the 50 hp 'Iskra' ('Spark') seven-cylinder bi-rotary engine (believed to be privately built by Brzeski in the Siemens factory), which drove huge contra-rotating two-blade airscrews.
   The Aquila, equipped with the unique Brzeski powerplant and one of the first in the world to employ contra-rotating propellers, was rolled out on Wiener-Neustadt aerodrome for the first time on 18 September, 1910, on the occasion of the Imperial review of Austrian aviation by the Emperor Franz Josef. The machine, provided with three seats and very well built, was described by the contemporary press as one of the most impressive among the 23 aircraft assembled for the review. The Emperor showed particular interest in it and, talking to Brzeski, expressed satisfaction that Poles had begun work in the field of aeronautics and wished them every success. Some days later the Aquila monoplane began its trials. Unfortunately it was destroyed in a crash soon after take-off on its first flight, the complicated and ineffective control system being presumably the cause of this mishap. It is believed that the Schindler brothers and Brzeski evolved further aircraft projects at the time, but details of these are lacking.
   After the war Brzeski continued his work on bi-rotary engines in Poland. During the 'twenties he designed a few experimental power units of this type, and a prototype of his 120-125 hp radial engine, which had five parallel cylinders mounted horizontally and was of exceptionally small overall diameter, was completed by the Pocisk factory in Warsaw in 1926. The engine ran successfully on a test stand for many hours and showed great promise. The Polish Skoda Works contemplated its quantity manufacture, but lack of orders prevented this.

Construction: The Aquila was a three-seat open-frame wire-braced high-wing monoplane of bamboo construction. The wing, of elliptical planform, was a fabric-covered double-surfaced multi-spar structure and incorporated a warping system which controlled lateral stability. The wing was attached to the top of the fuselage frame and heavily braced with wires to cabanes above and below the wing and to the fuselage frame. The triangular-section open bamboo frame constituted the fuselage and carried three seats in tandem, the first seat being equipped with an inclined steering wheel. The positioning of the seats, situated unusually far aft, and of the fuel tank, which was carried under the fuselage frame between the first and second seat, was rather surprising as it was bound to result in a very considerable C.G. movement. An oil tank, with a small pump beneath, was attached to the top frame under the wing. The tail unit consisted of a one-piece horizontal stabilizer, the design and bracing of which was very similar to those of the wing and which also embodied a warping system. The wing- and tail-warping systems were linked together, and various combinations of movements of these surfaces were to provide the means of control in all three planes. The landing gear, reminiscent of that of the Bleriot Type No. XI, consisted of two front wheels and a tailwheel, all wheels being provided with spring shock-absorbers. Overall dimensions included a span of 10 m (32 ft 9 3/4 in) and a length of 10 m (32 ft 9 3/4 in). Estimated emptv and maximum loaded weights were in the region of 300 kg (661 lb) and 550 kg (1,212 lb).