IS-4 Jastrząb

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

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

Development

The IS-4 was built for aerobatics with a high structure strength and a very high maximum speed which could not be achieved in a vertical dive. Due to the pilots 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.

Variants

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

Specifications (IS-4 Jastrząb bis)

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

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; 243 kn)
  
• Rough air speed max: 2,300 km/h (1,429.2 mph; 1,241.9 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 500 km/h (310.7 mph; 270.0 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

• Vogt Lo 100

References

• 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 Primarily English with 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

External links

• http://www.piotrp.de/SZYBOWCE/pis4.htm
• http://kionastore.com/plan-1530.html
• http://www.vintagesailplanes.de/szd__4.htm