Samolot Sp.I was a type of aircraft designed in

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

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

Design and development

The designer of the Samolot Sp.I 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 (early on also ''pursuit aircraft'') are military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air supremacy, air superiority of the battlespace. Domina ...

and, in addition, to demonstrate to the Government that high performance aircraft could be built with Polish materials. The Samolot Sp.I 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 wings. 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 wings. A monoplane has inherently the highest efficiency and lowest drag of any wing con ...

. 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 SPARS was the authorized nickname for the United States Coast Guard (USCG) Women's Reserve. The nickname was derived from the USCG's motto, "—"Always Ready" (''SPAR''). The Women's Reserve was established by law in November 1942 during Wor ...

and was covered with

plywood Plywood is a composite material manufactured from thin layers, or "plies", of wood veneer that have been stacked and glued together. It is an engineered wood from the family of manufactured boards, which include plywood, medium-density fibreboa ...

, 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 struts, 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 engine, reciprocating type internal combustion engine, internal combustion engine configuration in which the cylinder (engine), cylinders "radiate" outward from a central crankcase like the spokes of a wheel. ...

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 (or cowl) 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 ...

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 o ...

, tapering to the rear. The pilot's open

cockpit A cockpit or flight deck is the area, on the front part of an aircraft, spacecraft, or submersible, from which a pilot controls the vehicle. The cockpit of an aircraft contains flight instruments on an instrument panel, and the controls th ...

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.I's

tailplane A tailplane, also known as a horizontal stabilizer, is a small lift (force), 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

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. F ...

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

elevator An elevator (American English) or lift (Commonwealth English) is a machine that vertically transports people or freight between levels. They are typically powered by electric motors that drive traction cables and counterweight systems suc ...

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

Poznań Poznań ( ) is a city on the Warta, River Warta in west Poland, within the Greater Poland region. The city is an important cultural and business center and one of Poland's most populous regions with many regional customs such as Saint John's ...

-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, airship, or other vehicle that moves through a fluid medium (usually air or water). On an airplane, the rudder is used primarily to counter adverse yaw ...

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, develope ...

, 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 dome ...

, 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