Ilić Ilindenka

The Ilić Ilindenka was a series of Yugoslavian standard class sailplanes capable of aerobatics.

Ilindenka 1
Role single seat, high performance, standard class sailplane
National origin Yugoslavia
Manufacturer 20 May, Ivo Lola Ribar '43, Skopje
Designer Miloš Ilić
First flight 1953
Number built 3+

Design

The single seat, standard class (15 m (49 ft 3 in)) span) Ilindenka was, like most of its contemporaries, an all-wood sailplane. It had a cantilever, twin spar, shoulder wing with plywood skin around its leading edge ahead of the forward spar. The wing was trapezoidal in plan, with taper on both edges, and set with 2.5° of dihedral.[1] Ailerons occupied about half the trailing edges and Schemp-Hirth type spoilers were mounted at 40% chord.[2] Each wing was braced by a thin strut between rear spar and lower fuselage.[1]

The Ilindenka had an oval section, ply-skinned forward fuselage, becoming more rectangular aft. Its cockpit was at the wing leading edge, under a single piece canopy with a fairing behind it which fell away into the upper rear fuselage. Its tall fin was rounded in profile, with a horn balanced rudder of similar area. Its tailplane was mounted well forward on the fin just above the fuselage and carried elevators of similar area to it.[1][2]

It landed on a skid under the forward fuselage.[1]

Variants
Ilindenka 1
[2]
Ilindenka 1T
[2]
Ilindenka 2
[3][4]

Operational history

The Iindenka first flew in 1953 and was certified to fly loops, rolls and spins.[2] Production numbers are not known but the Airforce Museum in Belgrade holds two examples, though neither was on display in 2009.[5] Photographs show another, earlier example[2] and one with a later registration identified as an Ilindenka 2. Externally, the latter shows little difference from the Ilindenka 1 but there is little information on this variant.[3][4]

One Illindenka, flown by Zvonimir Rain, was Yugoslavia's sole Standard Class contestant at the 1958 World Soaring Championships, held in California. It was placed 12th out of 24.[6]

Specifications (Ilindenka 1)

Data from The World's Sailplanes[2]

General characteristics

  • Crew: one
  • Wingspan: 15.16 m (49 ft 9 in)
  • Wing area: 14.2 m2 (153 sq ft)
  • Aspect ratio: 16.2
  • Airfoil: Göttingen Gö 549-M (root), TsAGI 731-M (tip)
  • Empty weight: 187 kg (412 lb)
197 kg (434 lb) equipped
  • Max takeoff weight: 310 kg (683 lb)

Performance

  • Maximum speed: 230 km/h (140 mph, 120 kn) terminal velocity air brakes open
  • Never exceed speed: 230 km/h (140 mph, 120 kn)
  • g limits:
  • +5.6 at 52.4 km/h (32.6 mph; 28.3 kn)
  • +5.7 at 74 km/h (46.0 mph; 40.0 kn)
  • +1 at 230 km/h (142.9 mph; 124.2 kn) (VNE)
  • -2.85 at 102 km/h (63.4 mph; 55.1 kn)
  • Maximum glide ratio: 27.5 at 75 km/h (47 mph; 40 kn)
  • Rate of sink: 0.70 m/s (138 ft/min) min.at 66.5 km/h (41.3 mph; 35.9 kn)
  • Wing loading: 21.8 kg/m2 (4.5 lb/sq ft) max.

References
  1. Taylor, John W R (1960). Jane's All the World's Aircraft 1960-61. London: Sampson Low, Marston & Co. Ltd. p. 410.
  2. Wilkinson, K.G.; Brooks, Peter; Shenstone, B.S. (1958). The World's Sailplanes - Die Segelflugzeuge der Welt - Les Planeurs de le Monde (in English, German, and French). I. Organisation Scientifique et Technique International de Vol à Voile (OSTIV) & Schweizer Aero-Revue. pp. 196–200.
  3. "Ilindenka 2". Retrieved 15 December 2019.
  4. "Ilindenka 2 original layout". Retrieved 15 December 2019.
  5. Ogden, Bob (2009). Aviation Museums and Collections of Mainland Europe. Air Britain (Historians) Ltd. p. 505Photographs show another. ISBN 978-0-85130-418-2.
  6. "1958 WORLD SOARING CHAMPIONSHIPS" (PDF). Soaring: 14–5. July–August 1958.
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