Effect Of Helicopter Drag Reduction On Rotor Dynamic Loads And Blade Life

Helicopter drag as reflected in rotor propulsive force requirements has a significant effect on dynamic blade loads which can affect blade life. These loads also generate excitation for airframe vibrations. A detailed analysis has been made to assess the impact of helicopter drag on blade and rotor hub loads. Predicted dynamic loads are presented for a 16,000 pound helicopter with a four-bladed stiff-inpiane hingeless rotor flying at 150 knots with airframe (including hub and pyloii) parasite drag levels between 0 and 30 square feet of equivalent flat-plate drag area. The analysis used is described briefly and correlation with flight data shown. The significance of dynamic loads on blade life and airframe vibration are discussed. Reduction of airframe drag level decreases vibration excitation and blade loads significantly, which can result in opportunity for weight reduction and a secondary impact on extension of blade life.