IIL IS-12

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IS-12 and IS-13
Role Experimental two seat
trainer glider
National origin Romania
Manufacturer Întreprinderea de industrie Locală (IIL)
Designer Iosif Șilimon
First flight 23 December 1960
Number built 1 IS-12 and 1 IS-13

The IIL IS-12 was a two-seat glider, designed and built in Romania in 1960. It had a wooden wing but a metal fuselage and was constructed in parallel with the all-wood IS-13 for comparative tests. It was later followed by the IS-13a, a version with an all-metal wing.

Design and development

From about 1950 to his death in February 1981, Iosif Silimon was Romania's most prominent glider designer, his aircraft distinguished by his initials.

sailplane with a wooden wing and metal fuselage. The IS-13 a variant had a wooden fuselage of slightly changed shape, otherwise differing only in its empennage.[2]

The

chord just inboard of the ailerons. The wing tips carried the small, streamlined bodies known as salmons, common at the time.[3]

The fuselages of both the IS-12 and the IS-13 had oval cross sections, though the IS-12's was narrower by about 20% and correspondingly smaller in area. The IS-12's forward fuselage was a metal

perspex canopy in two parts, stretching from a little behind the nose into the wing leading edge. The forward part opened sideways and the aft section was rear hinged. The underside of the IS-13's fuselage curved smoothly, gradually decreasing the diameter towards the tail but that of the IS-12 narrowed more abruptly under the wing. Both models had a short landing skid under the forward fuselage and a semi-recessed, fixed and unsprung monowheel under the wing and fitted with a brake.[2][3]

Both aircraft had similar but not identical conventional

elevators was not needed. Both models had a trim tab on the starboard elevator and a tail bumper under the rudder Overall the S-13 was 400 mm (15.7 in) longer.[3]

Despite the different construction and the empennage alterations, the fuselage weights of the two aircraft were very similar with the IS-13 heavier by 5%, so their overall empty weights were the same to within under 2%.[3]

The IS-12 was first flown on 23 December 1960 and the IS-13 flew four days later. The intention was to compare the two in flight testing and select one for production[2] but there is no record of the latter. The performance figures of the two aircraft were almost identical, though the IS-13 had a marginally (2%) lower minimum sink rate.[3]

Five years later a version known as the IS-13a was flown. This had a metal wing of greater (16 m (52 ft 5.9 in)) span, giving it a much improved gliding angle of 35:1. It had a shorter fuselage than either the IS-12 or IS-13, but its method of construction is unknown.[4]

Variants

IS-12
Metal fuselage, wooden wings and empennage. Flown December 1960.
IS-13
Wooden fuselage, wings and empennage. Small changes to tail and a smoother fuselage underside line. Flown December 1960.
IS-13a
Longer span, all-metal wing only 7.10 m (23 ft 3.5 in) long. Best gliding angle of 35:1. Flown 1965.

Specifications (IS-12)

Data from Sailplanes of the World, pp. 206–7[3]

General characteristics

  • Crew: Two
  • Length: 7.60 m (24 ft 11 in)
  • Wingspan: 15.0 m (49 ft 3 in)
  • Wing area: 18.0 m2 (194 sq ft)
  • Aspect ratio: 12.5
  • Airfoil: NACA 43015 root, 43012A tip
  • Empty weight: 290 kg (639 lb)
  • Gross weight: 480 kg (1,058 lb)

Performance

  • Stall speed: 58 km/h (36 mph, 31 kn)
  • Never exceed speed: 200 km/h (120 mph, 110 kn) placard, in smooth air
  • Rough air speed max: 150 km/h (93 mph; 81 kn)
  • Aerotow speed: 130 km/h (81 mph; 70 kn)
  • Winch launch speed: 90 km/h (56 mph; 49 kn)
  • g limits: +5/-3
  • Maximum glide ratio: best 24 at 81 km/h (50 mph; 44 kn)
  • Rate of sink: 0.92 m/s (181 ft/min) minimum, at 65 km/h (40 mph; 35 kn)
  • Wing loading: 26.6 kg/m2 (5.4 lb/sq ft)


References

  1. ISBN 0710607059
    .
  2. ^ a b c Taylor, John W R (1964). Jane's All the World's Aircraft 1964-65. London: Sampson Low, Marston & Co. Ltd. p. 372.
  3. ^ a b c d e f Shenstone, B.S.; Wilkinson, K.G. (1963). The World's Sailplanes. Vol. II. Organisation Scientifique et Technique Internationale du Vol à Voile (OSTIV) and Schweizer Aero-Revue. pp. 206–9.
  4. ISBN 0 354 00067 5
    .
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