CNIAR / IAR Lark IS-29 / 31
ICA-Brasov IS-29 / IS-31
The IS-29, designed by a team under Dipl Ing losif Silimon, is an attempt to create a multi-role high performance single-seater suited to a variety of requirements and soaring conditions, and is offered in Standard Class (IS-29B and IS-29D) versions with 15m span wings, in Open Class form as the IS-29E with increased span wings and the IS-29G for club use with 16.5m span wings.
All versions have an identical fuselage and tail unit, differing mainly in the wing fitted, and are basically similar to the IS-28B2 with the same all-metal construction and a similar T-tail. The IS-29B Standard Class version with 15m span all-wooden wings was the first to fly, in April 1970, and was certificated in September that year; the prototype has a three-piece wing with constant chord centre section and tapered outer panels, and 'salmon' fairings on the wing tips.
The IS-29B was succeeded by the Standard Class IS-29D which had all-metal wings of the same span and first flew in November 1970. About 30 had been built by 1974 and from 1976 the production version was the IS-29D2, which features an improved cockpit and controls, Hutter air brakes, a separate tailplane and elevator instead of the earlier all-moving tailplane, and an improved rigging system.
More than 60 of this variant had been sold in Australia and the USA and the IS-29D4, which appeared in 1977, had provision for water ballast.
The Open Class IS-29E first flew in August 1971 with wings increased in span to 17.60m (57ft 9in), and fitted with flaps and Schempp-Hirth- air brakes as well as integral water ballast tanks.
The production version of the E is the IS-29E3, also known as the IS-31,with 20m (65ft 7.5in) span wings, and a 19m span (62ft 4in) version, the IS-29E2, was under development in 1977, while the IS-29E4 is a 24m span version. The club version is the IS-29G, also known as the IS-29D3, which has all metal 16.5m span (54ft 1.5 in) wings; this first flew in 1972, and the E2 and E3 variants have slightly different Wortmann wing sections to those of the IS-29D2.
All versions except the IS-29B have all metal shoulder wings with a main spar, false rear spar and riveted dural skin. The full-span flaps and ailerons are coupled to operate in unison but the flaps can be disconnected for separate operation during landing. The D2's Hutter air brakes are in the upper surface of the wings only, those of the other models being in the upper and lower surfaces. The all-metal semi-monocoque fuselage is the same for all versions except for local variations at the wing attachment points, and there is a detachable glassfibre nosecap. The retractable monowheel has a brake and there is a fixed tailwheel. The cockpit canopy hinges side-ways to starboard and can bejettisoned in flight. The IS-29D3 Club version has a fixed undercarriage and unpainted (all-chrome) finish. The IS-29D4 15m Class version has a maximum flap setting of 80° and air brakes, and will later be offered with 26.4 Imp gallons of water ballast.
The IS-29E2 19m span version has interconnected flaps and ailerons, and will be offered with 22 Imp gallons of water ballast. The IS-29E4 has a wing of 24m span made in four sections, with interconnected flaps and ailerons, and carries water ballast.
The IS-29DM and IS-29EM are motorised versions of the IS-29D2 and IS-29E3 respectively. The IS-29DM and IS-29EM each have a 39hp Rectimo 4AR-1200 engine driving a Hoffman HOV42 propeller; the fuel capacity is 6 Imp gallons. A retractable tubular-sprung Tost monowheel is fitted to these versions, plus a Tost tailwheel. Production IS-29DMs and IS-29EMs were due to become available from mid-1980.
The IS-33 racing version has interconnected flaps and ailerons on its 15m span wings, and was to be offered with 33 Imp gallons of water ballast.
The IS-31(E3) is a version of the IS-29 with 20m span wings and interconnected flaps and ailerons; it was to be offered with 33 Imp gallons of water ballast. The prototype has flown but had not been certificated by mid-1979.
To 6/30/81, 300 had been built. 1982 Standard price US$17,500.
Span: 49 ft 2.5 in
Length: 24 ft 2.5 in
Height: 5 ft 6.25 in
Wing area: 111.9 sq ft
Max wt: 795 lb.
Standard empty wt: 509 lb.
Max useful load: 286 lb.
Min sinking speed: 1.41 ft/sec at 50 mph / 114 fpm at 42 kts
Max speed: 120 kts.
Wing aspect ratio: 21.5.
Stalling speed: 37 kts.
Glide ratio (L/D): 37:1 at 50 kts.
Best glide ratio: 48:1 at 58 mph
Stalling speed: 37 kts.
Rough-air airspeed: 120 kts.
Max speed: 155 mph (in smooth air)
Wing loading: 6 lbs/sq.ft.