Rubik R-23 Gébics

In 1954 the Central Workshop of the Hungarian Aeronautical Association, Dunakeszi (MRSzE) was required to design and build a single seat training glider with pleasant handling characteristics but the performance to take a novice pilot to their C-certificate. The design team was headed by Ernő Rubik.[1] During its design and construction the management of the Dunakeszi workshops changed along with its name, becoming the Alagi Központi Kisérleti Üzem (AKKÜ) (Central Experimental Plant, Alag) in 1955.[2] The R-23 Gébics first flew on 13 June 1957.[1]

Structurally, the Gébics was all-metal, largely built from light-alloy members anodized against corrosion though steel tubes were used in highly stressed parts. The two-part wing was rectangular in plan apart from quadrantal tips and was mounted with 3° of dihedral. Each half-wing was built around a single dural spar at 30% chord, forward of which the wing was dural-covered, with chord-wise corrugations at a pitch of 150 mm (5.91 in), producing a torsion-resistant D-box. Behind the spar the wing was fabric-covered. The Gébics had broad-chord Frise-type ailerons occupying about half the span, their gaps increasing outwards.[1][3]

The fuselage of the Gébics was a largely dural pod-and-boom structure, though the rear fuselage or boom was quite deep and wide. The central structure was a vertical, trapezoidal, U-section frame, its upper part reinforced with welded steel tubes that included attachment points for the wing spar. From its base a box-keel reached forward to the nose, braced by an arched frame which leaned backwards and joined to the vertical frame under the wing. The Gébics' unusual fan-like airbrakes, sometimes described as bat wing type, were pivoted within the vertical frame and opened into a quadrant from fuselage to the wing underside, with a radius of about 750 mm (30 in). The pilot's seat was mounted on the keel between the vertical and leaning frames under a one-piece, side opening canopy. The underside of the keel carried a landing skid over its full length, with an unsprung, fixed monowheel placed behind the c.g.. The boom was a tapering, circular-section, riveted monocoque structure carryimg the Gébics' V-tail, which had parallel chord, forward-swept, metal-covered tailplanes set at 90° to each other. The control surfaces were fabric-covered. After development flights, these surfaces were extended in length, their forward sweep removed, separations increased to 108° and the control surfaces givene large aerodynamic balances. Below, there was a small tailskid.[1][3]

The R-24 Bibic (Lapwing) was identical to the Gébics apart from its wing. This had a 15 m (49 ft 3 in) span to enable it to compete as a Standard Class glider, an area of 12.30 m² (132.4 sq ft) and aspect ratio of 18.3. It used the laminar flow NACA 64₃618 airfoil, though the wing structure was unchanged. When a government decision closed the AKKU, repurposing its factory, it left the unfinished Bibic abandoned.[1][2][4]

The Gébics before modification.

After its first flight in June 1957 the Gébics was put through a series of comparative tests with the Cinke (Titmouse), a Hungarian post-war revision of the pre-war DFS Olympia Meise. Below about 90 km/h (56 mph; 49 kn) performances were similar but as speeds rose the superior sinking speed of the Gébics became increasingly significant.[1]

It was then taken to a base in the Mátra mountains chosen for wave lift. Tests showed it to be a stable aircraft with good handling, even in rough air, and difficult to spin. Having demonstrated its suitability for wave lift flights, it stayed in the mountains for a time, investigating techniques for the optimal use of this lift source.[1]

R-23 Gébics

As described.

R-24 Bibic

As R-23 but Standard Class, with a 15 m (49 ft 3 in) span, laminar flow wing. Not completed.[1][2][4]

Data from Gabor, F[1]

General characteristics

• Crew: One
• Length: 7.5 m (24 ft 7 in)
• Wingspan: 13.0 m (42 ft 8 in)
• Wing area: 13.0 m² (140 sq ft)
• Aspect ratio: 13.0
• Airfoil: Modified Göttingen Gö-549
• Empty weight: 168 kg (370 lb)
• Gross weight: 264 kg (582 lb)

Performance

• Maximum speed: 190 km/h (120 mph, 100 kn) with airbrakes open
• Stall speed: 52 km/h (32 mph, 28 kn)
• Maximum glide ratio: 21.1 at 74 km/h (46 mph; 40 kn)
• Rate of sink: 0.85 m/s (167 ft/min) minimum at 65 km/h (40 mph; 35 kn)