| R-31 Dupla | |
|---|---|
 | |
| Role | Two-seat training glider |
| National origin | Hungary |
| Manufacturer | Begun by the designer, completed in the workshop of the National Civil Defence Association (MHSz), Budaörs |
| Designer | Ernő Rubik |
| First flight | 1983 |
| Retired | 1986 |
| Number built | 1 |
The Rubik R-31 Dupla (Double) was a Hungarian side-by-side seat training glider first flown in 1983. Disappointing performance and vibration problems prevented it going into production.
Ernő Rubik had designed many gliders but by the 1980s had been retired a long time. His Dupla was intended as a light, low cost basic trainer to replace his widely used R-26 Góbé, which was coming to the end of its useful life having entered service in 1963. He began its construction in his own garage but later the Hungarian Defence League (Magyar Honvédelmi Szövetség or MHSz) offered help in their Budaörs workshops. It was first flown in 1983. [1]
The Rubik R-26 Góbé is a family of Hungarian shoulder-wing, two-seat training gliders that was designed by Ernő Rubik Sr., and produced by Auto-Aero. After its introduction the R-26 Góbé became the de facto training glider type in Hungary and is still used by many clubs for basic instruction.
Budaörs is a town in Pest county, Budapest metropolitan area, Hungary.
The Dupla had a mid-mounted wing of rectangular plan out to rounded tips. The half-wings were built around single dural spars with Rubik's characteristic corrugated skin, first used some twenty-five years earlier on the R-23 Gébics, ahead of it around the leading edge forming a torsion resistant D-box. Diagonal, internal drag struts took loads from spar to fuselage. Behind the spar the wing was fabric covered. Small underwing skids protected the tips. Slotted ailerons, occupying about 40% of the trailing edge, projected a little beyond the tips, where they were upswept. Immediately inboard of the ailerons there were trailing edge mounted split-flap-type airbrakes with extreme deflections of ±90° The inboard third of the trailing edge had conventional slotted flaps. [1]
In a fixed-wing aircraft, the spar is often the main structural member of the wing, running spanwise at right angles to the fuselage. The spar carries flight loads and the weight of the wings while on the ground. Other structural and forming members such as ribs may be attached to the spar or spars, with stressed skin construction also sharing the loads where it is used. There may be more than one spar in a wing or none at all. However, where a single spar carries the majority of the forces on it, it is known as the main spar.
The Rubik R-23 Gébics (Shrike) was a Hungarian advanced training glider, the first of a series of metal-framed gliders designed by Ernő Rubik, though only one Gébics was built.
The leading edge is the part of the wing that first contacts the air; alternatively it is the foremost edge of an airfoil section. The first is an aerodynamic definition, the second a structural one. As an example of the distinction, during a tailslide, from an aerodynamic point of view, the trailing edge becomes the leading edge and vice versa but from a structural point of view the leading edge remains unchanged.
The Dupla's forward fuselage was built around a tubular structure and covered in a mixture of light-metal and canvas. Pupil and instructor sat side-by-side, sharing some controls. There was a single, control column, operated by individual levers in front of each seat via a parallelogram linkage and the airbrake lever was on the centreline of the fixed, rear part of the cockpit transparencies. The forward part of the canopy hinged open. Behind the wing the fuselage was a slender cone covered with dural plate and tapering to a conventional tail with a short but broad fin. A triangular tailplane was strut-braced to it, well above the fuselage, and carried essentially rectangular fabric covered elevators. The fin also mounted an angular, balanced rudder which, like the elevators, was fabric covered. [1]
In Euclidean geometry, a parallelogram is a simple (non-self-intersecting) quadrilateral with two pairs of parallel sides. The opposite or facing sides of a parallelogram are of equal length and the opposite angles of a parallelogram are of equal measure. The congruence of opposite sides and opposite angles is a direct consequence of the Euclidean parallel postulate and neither condition can be proven without appealing to the Euclidean parallel postulate or one of its equivalent formulations.
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. Fins are also used to increase surface areas for heat transfer purposes, or simply as ornamentation.
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 gyroplanes. Not all fixed-wing aircraft have tailplanes. Canards, tailless and flying wing aircraft have no separate tailplane, while in V-tail aircraft the vertical stabiliser, rudder, and the tail-plane and elevator are combined to form two diagonal surfaces in a V layout.
The principal landing gear was a fixed monowheel aft of mid-chord. Forward of it, a skid protected the fuselage underside, assisted by a small tailskid on an extension of the fin below the fuselage. [1]
Landing gear is the undercarriage of an aircraft or spacecraft and may be used for either takeoff or landing. For aircraft it is generally both. It was also formerly called alighting gear by some manufacturers, such as the Glenn L. Martin Company.
In aeronautics, a chord is the imaginary straight line joining the leading and trailing edges of an aerofoil. The chord length is the distance between the trailing edge and the point on the leading edge where the chord intersects the leading edge.
Flying under only temporary certification, the Dupla made twenty-six flights, with a total of eight flight hours, between 1983 and 1986. Its performance was poorer than that of the Góbé it was intended to replace, its handling characteristics did not prepare students for gliders like the SZD-30 Pirat and vibration problems persisted at all speeds, so testing was terminated in 1986. [1]
The SZD-30 Pirat is a single-seat multi-purpose glider aircraft from the Polish firm PZL Bielsko, which first flew in 1966 and was produced beginning in 1967.
Budapest is the capital and the most populous city of Hungary, and the tenth-largest city in the European Union by population within city limits. The city had an estimated population of 1,752,704 in 2016 distributed over a land area of about 525 square kilometres. Budapest is both a city and county, and forms the centre of the Budapest metropolitan area, which has an area of 7,626 square kilometres and a population of 3,303,786, comprising 33 percent of the population of Hungary.
Data from Gabor,F (1988) [1]
General characteristics
Performance
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