Fatigue life of the main rotor blade of a helicopter is investigated under random loading. The blade is comprised of many different parts such as spar, skin, abrasive strip, doublers, box beam doublers, etc. and it supports complex random load spectra. A finite element analysis is carried out to extract the stress distribution in the blade parts. Small thickness of blade parts and the longitudinal twist of the blade make its modeling very complicated. At the next step, all the forces applied to the blade were calculated in hover situation and applied to the blade to obtain the stresses. Then, stress analysis was made and stress spectrum was derived for each main part of the blade using standard load spectrum, Felix. Then, using the Miner’s rule the fatigue life of the blade is estimated following different life estimation methods. Comparing the results, some conclusive results are drawn. The fatigue life of the blade was obtained to be 6165 hours, which is consistent with the minimum required life for helicopter dynamic parts.
