IS-4 Jastrząb

The IS-4 Jastrząb (Instytut Szybownictwa – gliding institute) was a single-seat aerobatic glider designed and built in Poland from 1949.

IS-4 Jastrząb
Role Glider
National origin Poland
Manufacturer Instytut Szybownictwa
Designer J Niespał
First flight 21 Dec 1949[1]
Introduction 1950
Number built 37[1]

Development

The IS-4 was built for aerobatics with a high structural strength and a very high maximum speed which could not be achieved in a vertical dive. Due to the pilot's sitting position and the arrangements of the controls, it was difficult for pilots to exceed the 8g loading limit. During high speed flight it was possible for the air-brakes to be sucked out violently, so most pilots ensured that they remained closed by holding the airbrake control.[1]

Variants
  • IS-4 Jastrząb – two prototypes built in 1949.[1]
  • IS-4 Jastrząb bis – Thirty-five production aircraft, three of which were exported.[1]

Specifications (IS-4 Jastrząb bis)

Data from The World's Sailplanes:Die Segelflugzeuge der Welt:Les Planeurs du Monde Volume II[1][2]

General characteristics

  • Crew: 1
  • Length: 6.25 m (20 ft 6 in)
  • Wingspan: 12 m (39 ft 4 in)
  • Height: 1.3 m (4 ft 3 in) at cockpit
  • Wing area: 12 m2 (130 sq ft)
  • Aspect ratio: 12
  • Airfoil: Root – NACA 2418, Tip – NACA 2412, Mid – NACA 0012
  • Empty weight: 240 kg (529 lb)
  • Gross weight: 357 kg (787 lb)

Performance

  • Stall speed: 67 km/h (42 mph, 36 kn)
  • Never exceed speed: 450 km/h (280 mph, 240 kn)
  • Rough air speed max: 200 km/h (124.3 mph; 108.0 kn)
  • Aerotow speed: 200 km/h (124.3 mph; 108.0 kn)
  • Winch launch speed: 150 km/h (93.2 mph; 81.0 kn)
  • g limits: +7 -4 at 200 km/h (124.3 mph; 108.0 kn)
  • Maximum glide ratio: 20.2 at 87 km/h (54.1 mph; 47.0 kn)
  • Rate of sink: 1.04 m/s (205 ft/min) at 70 km/h (43.5 mph; 37.8 kn)
  • Wing loading: 29.7 kg/m2 (6.1 lb/sq ft)

See also

Aircraft of comparable role, configuration, and era

References
  1. Piechowski, Piotr. "IS-4 Jastrząb". Piotr & Renate Piechowski. Retrieved 19 April 2013.
  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. 172–173.
  • Piechowski, Piotr. "IS-4 Jastrząb". Piotr & Renate Piechowski. Retrieved 19 April 2013.
  • 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. 172–173.

Further reading
  • Taylor, J. H. (ed) (1989) Jane's Encyclopedia of Aviation. Studio Editions: London. p. 29
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