Flight testing is necessary in the process of showing compliance of the airplane with specific design requirements. Utva Aviation Industry performed numerous flight tests of Sova airplane in order to prove its safety. Along with airplane design, structure, performance and equipment, it was necessary to show compliance of the powerplant. In this paper there is the analysis of the flight tests of the powerplant cooling in the most critical climbing case with maximum ambient atmospheric temperature for which approval is requested. Flight test report results are presented with defined minimum speed for these conditions proving our four-seater meets all requirements in its category.