This paper investigates the bending oscillation perpendicular to the plane of rotation of the unarticulated helicopter blade. The motion is comparable to the flapping of the hinged rotor blade. Two differential equations of motion are written in terms of two of the natural modes of the blades. The solutions of the equations are a pair of infinite Fourier series in terms of the position of the blade in azimuth. The series are approximated by their constant and first harmonic terms. Six simultaneous linear algebraic equations written in terms of flight and blade parameters give the six Fourier coefficients. A sample problem is carried through, beginning with thephysical characteristics of a blade and yielding the bending motion at a specific flight condition. The method can be expanded both to include a larger number of natural modes and to achieve a closer approximation to the infinite series solutions. There are included a sufficient number of variables to describe blades of current design.