The study of structural strength on aircraft wings is important because it involves flight safety. The Spar is the main component of an airplane wing which transmits most of the lift to the fuselage, so this research is focused on the strength of the spar. The research conducted is a study of the wing spar of Medium Altitude Long Endurance Unmanned Aircraft (MALE UAV) with a total mass of 1,300 kg, with a wingspan that is 16 m long, and must be able to withstand loads with a load factor of 4G. Alternative uses of material dimensions to make them lighter and stronger so that aircraft performance can be improved. The analysis was carried out by estimating the distribution of wing lifts using the Schrenk Approximation method. Mathematical calculations were carried out to determine the mechanical strength. The effect of the taper ratio not only applies to lift distribution, but also to its strength, and the taper ratio ≤0.4 is the value that meets the strengths in this study.