IS-3 ABC

The IS-3 ABC (Instytut Szybownictwa – Gliding Institute) was a single-seat training glider designed and built in Poland from 1947.

IS-3 ABC
IS-3 ABC-A in the Polish Aviation Museum
Role Glider
National origin Poland
Manufacturer Instytut Szybownictwa
First flight 31 December 1947
Introduction 1948
Retired 1961
Number built 256[1]

Development

From 1946 the IS (Gliding Institute) started work on designing gliders to rebuild the shattered by the war Polish gliding movement. Four types were required:

  • 1. School (IS-3 ABC)
  • 2. Transition (IS-A Salamandra)
  • 3. Training and intermediate performance (IS-2 Mucha)
  • 4. High performance / advanced (IS-1 Sęp)

To fulfil the 'School' requirement the IS-3 ABC primary glider was designed by Rudolf Matz and Roman Zatwarnicki, and built at the workshops in Bielsko.

Using the sole remaining W.W.S.1 Salamandra as a starting point, the IS-3 ABC emerged looking similar to most primary gliders, with a high set rectangular low aspect ratio wing, wire-braced to an open structure wire-braced fuselage, which did nothing more than connect the seat, skid and tail unit to the wings.

The IS-3 ABC prototype first flew on New Year's Eve of 1948 by Peter Mynarski and after successful trials, a production commenced as the IS-3 ABC-bis. Further improvements resulted in the IS-3 ABC-ter, with a cabin and windscreen for the pilot. Last and most numerous variant was ABC-A of 1955, produced in 1956-57. 256 of all variants were manufactured in workshops in Bielsko (of IS, later SZD), Krosno and Lubawka[1] (according to other publications, 280, including 74 bis, 30 ter and 176 A[2]).

Polish instructors were also instrumental in boosting the gliding movement in the People's Republic of China, providing instruction and advice with the 50 IS-3 ABC A's exported there. This variant was modified with less dihedral (1°),[3] to allow the generally shorter Chinese students to hold the wings level for take-off. After flight trials in Poland it was confirmed that the it did not appreciably affect the handling. The Chinese also manufactured these gliders on the licence.

The IS-3 ABC series was in use at Polish state gliding clubs up to 1961, when the dual training syllabus was finally introduced. Many of the IS-3 primary gliders were dispersed to schools and clubs for use as training aids, some of which survive as exhibits in museums today.


Variants
  • IS-3 ABC – The sole prototype aircraft without folding wings.
  • IS-3 ABC bis – production aircraft with reduced wing incidence, increased aileron movement and with folding wings and tail-unit (24 made in IS and 50 in Lubawka[2][3]).
  • IS-3 ABC ter – version equipped with a removable cockpit nacelle and windscreen as well as fixed wings and tail-unit (30 made in Lubawka[2][3])
  • IS-3 ABC-A – last production version, with less wing dihedral, produced in 1956-57 (most in Krosno).


Specifications (IS-3 ABC-A)

Data from http://www.piotrp.de/SZYBOWCE/pis3.htm

General characteristics

  • Crew: 1
  • Length: 6.27 m (20 ft 7 in)
  • Wingspan: 9.0 m (29 ft 6 in)
  • Height: 1.72 m (5 ft 7 in)
  • Wing area: 13.5 m2 (145.3 sq ft)
  • Aspect ratio: 6:1
  • Airfoil: Peyret 16%
  • Empty weight: 105 kg (231.5 lb)
  • Gross weight: 185 kg (408 lb)

Performance

  • Maximum speed: 135 km/h (84 mph, 73 kn)
  • Stall speed: 45 km/h (28 mph, 24 kn)
  • Maximum glide ratio: 9.2 @ 53 km/h (29 kts / 33 mph)
  • Rate of sink: 1.5 m/s (295 ft/min)
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See also

References
  1. (in Polish) Krzyżan, Marian, Samoloty w muzeach polskich (Aircraft in the Polish museums), Warsaw: Wydawnictwa Komunikacji i Łączności, 1983, ISBN 978-83-206-0432-0, p. 132-133
  2. Babiejczuk, Janusz and Grzegorzewski, Jerzy. Polski Przemysł Lotniczy 1945-1973 (in Polish). Warsaw: Wydawnictwo MON, 1974. No ISBN, p. 118
  3. IS-3 ABC
  • Taylor, J. H. (ed) (1989) Jane's Encyclopedia of Aviation. Studio Editions: London. p. 29
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