| Skraba S.T.3 | |
|---|---|
 | |
| Role | Two-seat sport and touring aircraft |
| National origin | Poland |
| Manufacturer | C.W.L. (Centralne Warsztaty Lotnicze - central aviation workshops) |
| Designer | Boleslaw Skraba |
| First flight | July 1927 |
| Number built | 1 |
The Skraba S.T.3 was a two-seat Polish biplane built in 1928. It was the first all-metal aircraft designed in Poland; only one was completed.
Bolesław Skraba (born 1894), a former Austro-Hungarian pilot during the First World War, was one of the most experienced Polish flight instructors in early interwar period, and also the test pilot in C.W.L. (central aviation workshops) in Warsaw. One of his greatest ambitions at that time was to establish an aircraft range record on a Polish-made plane. Building of Skraba S.T.3 was his private initiative, as it was mainly designed to achieve the mentioned goal.
The S.T.3 had a duralumin structure and was a sesquiplane; though the lower wing had a span only slightly less than the upper, its chord was reduced to 60%. The lower wing was also aerodynamically thinner than the upper. Both wings were in two parts and had blunted rectangular plans. They were built around two girder spars, with dural skin around the leading edges and fabric covered elsewhere, including the full-span ailerons which were mounted on the upper wing only. The S.T.3 was a single bay biplane with extreme stagger, braced on each side by a single streamlined, forward-leaning interplane strut with wide extremities connecting to both forward and aft spars. The upper wing was held over the fuselage with a cabane of two transverse inverted V-struts from the spars at the central wing joint to the upper fuselage longerons. The lower wings were attached to the lower longerons. [1] [2]
The underlying fuselage structure was a rectangular section girder frame of dural tubes. This tapered in the nose into mountings for the 30 kW (40 hp) nine-cylinder Salmson 9AD radial, though this engine was slow to arrive and the first flights were made with a 34 kW (45 hp), six-cylinder Anzani 6 radial. The S.T.3 was designed to make long distance, possibly record-setting, flights and a large fuel tank was fitted within a bulbous underside. Well behind the engine there was a long, open cockpit with two seats in tandem, the forward one over the lower wing and with a cut-out in the upper wing trailing edge to improve the field of view. The S.T.3 was flown solo from the rear seat, which had a headrest in a fairing stretching back to the tail, but dual control was fitted. The forward fuselage from the engine to the rear of the cockpit was given a rounded section with dural plating but aft that form was continued by fabric covering over duralumin stringers. [1] [2]
The S.T.3 had conventional tail, with an elliptical plan, wire braced tailplane and elevators mounted on top of the fuselage. Its fin was triangular, carrying a rudder which ran down to the keel and worked in a small elevator cut-out. [1] [2]
The landing gear was fixed and conventional, with large wheels on a single axle with a track of 1.40 m (55 in). The axle was mounted via rubber cords to a V-strut on each side. Its tall wooden tailskid was also rubber cord sprung. [1] [2]
The uncovered fuselage of the S.T..3 was exhibited in May 1927 at the Warsaw Aviation Exhibition and the aircraft first flew in July. The Salmson engine was fitted by October when it flew in the National Lightplane Contest. By then it had a revised windscreen and faired-in undercarriage legs. Flown by Skraba, it was placed fifth of six. [2]
It underwent a major rebuild at the start of 1928 in which the span was increased by 800 mm (31.5 in) and the length by 200 mm (7.9 in). The changes to the wing dimensions increased the wing area by 7.6%. The tail surfaces were also enlarged, the belly tank removed, upper decking lowered and the structure generally refined to decrease weight. The modified machine was complete by 12 May 1928. That September it took part in the 2nd National Lightplane Contest. It failed to improve its previous rating, coming tenth out of twelve, but it did get an official award for its short (70 m (230 ft)) landing run. [2]
Even after the 1928 revisions the innovative S.T.3's performance was unimpressive and only one was built. Cynk claims it inspired the design of the DUS III Ptapta, another all-metal staggered biplane sports and touring aircraft. [2]
After personal tragedy (a sudden and unexpected death of his only son) Bolesław Skraba left the aircraft industry. He died in Warsaw in 1943.
Data from Les Ailes, February 1928 [1]
General characteristics
Performance
The Latécoère 6 was a French four-engined biplane bomber of the early 1920s. It was of advanced all-metal construction and probably the first aircraft to use geodetic construction. Only one was built.
The Hanriot H.31 was a single engine, single seat French biplane fighter aircraft built in 1925 to compete in a government programme. It was not successful and only one prototype was completed.
The Caudron C.140 was a French tandem cockpit sesquiplane designed in 1928 as a combination of liaison aircraft and observer and gunnery trainer.
The Les Mureaux 3 C.2 and Les Mureaux 4 C.2 were French two seat, parasol winged fighters, flown in 1927-8, which differed only in their engines. They were developed into near identical army co-operation types, the ANF Les Mureaux 130 A.2 and ANF Les Mureaux 131 A.2, in 1929–31.
The Peitz 101, aka Peitz Avionette, was a French amateur-built, all-metal light aircraft, first flown during the winter of 1931–32.
The Hanriot H.34 was a basic trainer designed in France in 1924 which did not reach production. It was a parasol wing aircraft, seating two in tandem.
The Hanriot H.46 Styx was a French, single-engined, parasol wing aircraft which could equally be configured for training, liaison or ambulance roles; in the latter form it was able to accept a patient on a stretcher. Several different engines were fitted and flown but the type did not reach production.
The Raab-Katzenstein RK.9 Grasmücke (Hedge-sparrow) was a 1920s German two-seat touring, advertising and training biplane. It was one of many designs from several countries aiming to provide low cost flying and was quite successful, with about twenty built.
The Morane-Saulnier MS.152 was a French multi-purpose aircraft built in 1928. It did not go into production.
The Medwecki HL 2 was a Polish two seat lightplane flown in 1927. Handicapped by a low power, unreliable engine, its flying life lasted little more than a month.
The Offierski O.2 was a one-off, two seat, low powered lightplane built in Poland on the late 1920s. It flew in 1928 but an old and unreliable engine prevented its development.
The Medwecki and Nowakowski M.N.3 or just M.N.3 was a low-powered, four seat, Polish aircraft flown in 1928. The sole example was modified into a more powerful two-seater which served aeroclubs until World War II.
The Rogalski and Wigura R.W.1 was designed and built by a pair of students at Warsaw Technical University in 1927. The single example was a two-seat parasol-wing monoplane which entered two national competitions, served the Warsaw Academic Aeroclub and also towed an advertising banner.
The D.K.D.3 was a Polish, single seat, parasol-wing sports aircraft first flown in 1927. Only one was built but flew in demonstrations and in national competitions into the early 1930s.
The Działowski D.K.D.4 was a Polish, parasol-wing, sports two-seater built in 1928. One won the Second National Lightplane Contest, with another coming fifth.
The Zalewski W.Z.XI Kogutek I was a basic, single seat sport aircraft designed and built in Poland in the 1920s. Its engine was also designed and built by Zalewski, making it the first all-Polish aircraft to fly.
The Grzmilas Orkan II was a Polish one-off, single-seat sports aircraft. It came second in the second National Lightplane Contest held soon after its first flight, with outstanding take-off and climb characteristics. Its designer and builder continued to use it until 1939.
The D.U.S. III Ptapta was a two-seat sports and touring biplane and only the second Polish aircraft using aluminium alloy construction.
The LKL IV and LKL V were a pair of very similar Polish parasol wing two-seaters, built in the early 1930s. They differed primarily in their engines.
The Sido S.1 was a Polish two seat, parasol wing trainer aircraft, first flown in 1930.
