The pilot project of new light civil turboprop aircraft, called the KhAI-90, featuring a cruising speed of 350km/h, payload of 600 kg at 500 km range, and equipped with two turboprop Rolls-Royce 250-B17F engines each with power of 420 hp (alternatively, two AI-450C engines each with power of 450 hp may be installed) is presented herein. Based on the developed technical task, the concept for creating the KhAI-90 new competitive light civil aircraft, and the analysis of prototypes’ aircraft parameters and characteristics, the main tactical and technical requirements are assigned. The take-off weight of the new aircraft is determined in three approximations at the preliminary design stage of light civil turboprop aircraft, using the iterative software “CLA-TOW”, studying the influence of the wing geometric parameters and lift devices on aerodynamic performance, the power-to-weight ratio and the airplane weight parameters. The following parameters are calculated for the design: minimum take-off weight