The Trener is a modified version of the LIBIS-18 single-seater Standard Class sailplane which first flew on 20 October 1964 and was designed by the Letalski Institut Branko Ivanus, Slovenija - LIBIS. Of wooden construction with cantilever shoulder mounted wings with tapered outer panels, the LIBIS-18 did not go into production.
The VTC Trener differs from it chiefly in having the all-moving tailplane mounted slightly higher on the sweptback fin and rudder, and an improved cockpit layout, the pilot sitting under a flush-fitting one-piece cockpit canopy. The Trener is also of all-wood construction, using beech and Swedish plywood, and has Wortmann wing sections giving a thickness/chord ratio of 18% at the root. The fuselage is a wooden monocoque with a non-retractable monowheel with a brake, andatailskid. An initial batch of 50 Treners is believed to have been ordered by the Yugoslav Aero Club, these being built by VTC at Vrsac.
Span: 49 ft 2.5 in
Length: 22 ft 7.75 in
Wing area: 139.6 sqft
Aspect ratio: 17.35
Max speed: 136.5 mph (in smooth air)
Max aero-tow speed: 93 mph
Min sinking speed: 2.36 ft/sec at 48.5 mph
Best glide ratio: 31:1 at 53 mph