The low-powered Samolot Sp.I, designed in

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populous ...

in the mid-1920s, was intended to explore the characteristics of a proposed single seat fighter. The project did not receive government support and only one Sp.1 was built.

Design and development

The designer of the Samolot Sp.1 was Piotr Tulacz, the technical director of Samolot. A private venture, it was intended to be a research development vehicle for a more powerful

fighter aircraft Fighter aircraft are fixed-wing military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air superiority of the battlespace. Domination of the airspace above a battlefield ...

and, in addition, to demonstrate to the Government that high performance aircraft could be built with Polish materials. The Samolot Sp.1 was a braced

parasol wing A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple planes. A monoplane has inherently the highest efficiency and lowest drag of any wing confi ...

monoplane A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple planes. A monoplane has inherently the highest efficiency and lowest drag of any wing confi ...

. Its two-part wing, rectangular in plan apart from blunted tips, was moderately thick. Each half-wing was built around a pair of wooden

spars The United States Coast Guard (USCG) Women's Reserve, also known as the SPARS (SPARS was the acronym for "Semper Paratus—Always Ready"), was the women's branch of the United States Coast Guard Reserve. It was established by the United States ...

and was covered with

plywood Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. It is an engineered wood from the family of manufactured ...

, then joined centrally and supported just above the fuselage on

cabane strut In aeronautics, bracing comprises additional structural members which stiffen the functional airframe to give it rigidity and strength under load. Bracing may be applied both internally and externally, and may take the form of strut, which act in ...

s. Primary wing bracing was provided on each side by a parallel pair of steel struts, enclosed in wooden streamlined cladding, from the lower fuselage to the wing spars. It had been designed to accept

radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ca ...

s in the power range and when the Sp.I was completed in the mid-1926 the only available engine was an elderly six-cylinder Anzani 6A-4 which gave . This was housed under a circular cross-section metal

cowling A cowling is the removable covering of a vehicle's engine, most often found on automobiles, motorcycles, airplanes, and on outboard boat motors. On airplanes, cowlings are used to reduce drag and to cool the engine. On boats, cowlings are a cove ...

with its cylinder heads protruding for cooling. The cowling blended smoothly into the rest of the fuselage which was a thick ply-skinned

semi-monocoque The term semi-monocoque or semimonocoque refers to a stressed shell structure that is similar to a true monocoque, but which derives at least some of its strength from conventional reinforcement. Semi-monocoque construction is used for, among ot ...

, tapering to the rear. The pilot's open

cockpit A cockpit or flight deck is the area, usually near the front of an aircraft or spacecraft, from which a Pilot in command, pilot controls the aircraft. The cockpit of an aircraft contains flight instruments on an instrument panel, and the ...

was just behind the

trailing edge The trailing edge of an aerodynamic surface such as a wing is its rear edge, where the airflow separated by the leading edge meets.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 521. Aviation Supplies & Academics, 1997. ...

of the wing, where there was a small cut-out to improve his field of view. The Sp.1's

tailplane A tailplane, also known as a horizontal stabiliser, is a small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplane ...

and

fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fin ...

were integral parts of the fuselage and also ply covered, as were the control surfaces; the

elevator An elevator or lift is a wire rope, cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or deck (building), decks of a building, watercraft, ...

s were divided. The Sp.I had a conventional, fixed

undercarriage Undercarriage is the part of a moving vehicle that is underneath the main body of the vehicle. The term originally applied to this part of a horse-drawn carriage, and usage has since broadened to include: *The landing gear of an aircraft. *The ch ...

with a track of . The mainwheels were on a single axle with rubber-cord shock absorbers, mounted on steel V struts from the fuselage at the base of the wing struts. These struts, like the wing bracing, were clad in wood streamlining. The first flight, flown by Samolot's chief test-pilot Edmond Holodynski at Poznan-Lawica, was in July 1926. Further flight-testing showed a lack of power but also some handling problems and instabilities. The latter were soon corrected by a reduction in fuselage length and some

rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally aircraft, air or watercraft, water). On an aircraft the rudder is used primarily to ...

modifications and the aircraft was re-engined with a

Salmson 9Ac Between 1920 and 1951 the Société des Moteurs Salmson in France developed and built a series of widely used air-cooled aircraft engines.Gunston 1986, p. 158. Design and development After their successful water-cooled radial engines, develop ...

, a nine-cylinder modern radial. As a result, the Sp.I handled well and bettered its calculated performance. Despite its good performance, Samolot failed to get Government funding and Sp.I development was abandoned. It did leave a legacy, in that some of the engineers who had worked on its design subsequently joined the design team of the successful

PWS-10 The PWS-10 was a Polish fighter aircraft, constructed in the PWS (''Podlaska Wytwórnia Samolotów'' - Podlasie Aircraft Factory). It was the first Polish-designed fighter to enter serial production. Design and development First work on a domes ...

, another braced parasol wing aircraft.

Specifications (Salmson engine)

References

{{reflist, refs= {{cite book, title=Polish Aircraft 1893-1939, last=Cynk, first=Jerzy, year=1971, publisher=Putnam Publishing, location=London, isbn=0 370 00085 4, page
352–4
url-access=registration, url=https://archive.org/details/polishaircraft1800cynk/page/352 Parasol-wing aircraft 1920s Polish experimental aircraft SP1 Single-engined tractor aircraft