URMV-3 IS-4

The IS-4 was a high performance glider designed by Iosif Şilimon and built in Romania in the late 1950s at the URMV-3 (Rom: Uzinele de Reparatii Material Volant-3 - Glider repair and manufacture factory) factory at Braşov.[1]

IS-4
Role Sailplane
National origin Romania
Manufacturer URMV-3[1]
Designer Iosif Şilimon[1]
First flight 5 June 1959
Developed from URMV-3 IS-3d

Design and development

The IS-4 high-performance glider followed the layout of the earlier IS-3d, constructed largely of wood with plywood and fabric skinning. The high-set cantilever wings with moderate dihedral (2º 30') were built with a single main spar with a plywood covered leading egdge torsion box. The ovoid section fuselage was of monocoque construction with plywood skin with a streamlined full-length cockpit canopyforward of the wings. The undercarriage consisted of a balloon main-wheel with nose and tail skids. Flying controls were largely conventional with plywood skinned fixed portions and fabric covered wooden built up movable surfaces. Pitch trim was achieved by a trim tab on the elevators and adverse yaw was alleviated through the use of differential ailerons.[1]

Very little is known of the IS-4s development or operational history.

Specifications (IS-4)

Data from The World's Sailplanes:Die Segelflugzeuge der Welt:Les Planeurs du Monde Volume II[2]

General characteristics

  • Crew: 1
  • Length: 7.1 m (23 ft 4 in)
  • Wingspan: 15 m (49 ft 3 in)
  • Height: 0.9 m (2 ft 11 in) at cockpit
  • Wing area: 14 m2 (150 sq ft)
  • Aspect ratio: 16
  • Airfoil: Root:Göttingen 549, Mid Göttingen 549, Tip Göttingen 693
  • Empty weight: 210 kg (463 lb)
  • Gross weight: 320 kg (705 lb)

Performance

  • Stall speed: 60 km/h (37 mph, 32 kn)
  • Never exceed speed: 200 km/h (120 mph, 110 kn) *Rough air speed max: 150 km/h (93 mph; 81 kn)
  • Aerotow speed: 120 km/h (75 mph; 65 kn)
  • Winch launch speed: 90 km/h (56 mph; 49 kn)
  • Terminal velocity: with full air-brakes at max all-up weight 185 km/h (115 mph; 100 kn)
  • g limits: +5 -3 at 250 km/h (135.0 kn)
  • Maximum glide ratio: 30 at 80 km/h (50 mph; 43 kn)
  • Rate of sink: 0.64 m/s (126 ft/min) at 41.6 mph; 36.2 kn (67 km/h)
  • Wing loading: 22.9 kg/m2 (4.7 lb/sq ft)

See also

Aircraft of comparable role, configuration, and era Grunau Baby Related lists List of gliders

Notes
  1. Gudju, Ion; Gheorghe Iacobescu; Ovidiu Ionescu (1974). Romanian Aeronautical Constructions 1905-1974. Bucharest. pp. 318–319.
  2. Shenstone, B.S.; K.G. Wilkinson (1963). The World's Sailplanes:Die Segelflugzeuge der Welt:Les Planeurs du Monde Volume II (in English, French, and German) (1st ed.). Zurich: Organisation Scientifique et Technique Internationale du Vol a Voile (OSTIV) and Schweizer Aero-Revue. pp. 192–193.

References
  • Shenstone, B.S.; K.G. Wilkinson (1963). The World's Sailplanes:Die Segelflugzeuge der Welt:Les Planeurs du Monde Volume II (in English, French, and German) (1st ed.). Zurich: Organisation Scientifique et Technique Internationale du Vol a Voile (OSTIV) and Schweizer Aero-Revue. pp. 192–193.
  • Gudju, Ion; Gheorghe Iacobescu; Ovidiu Ionescu (1974). Romanian Aeronautical Constructions 1905-1974. Bucharest. pp. 318–319.
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