IS-3 ABC

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.

• 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).

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 at 53 km/h (29 kts/33 mph)
• Rate of sink: 1.5 m/s (295 ft/min) at 48 km/h (26 kts/30 mph)

• W.W.S.1 Salamandra
• Slingsby Primary
• Lippisch Zögling

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

Wikimedia Commons has media related to IS-3 ABC.

• http://www.piotrp.de/SZYBOWCE/pis3.htm