  We consider electromagnetic radiation of a charged particle bunch moving
uniformly along a corrugated planar metallic surface. It is assumed that the
wavelengths under consideration are much larger than the period and the depth
of corrugation. Using the method of the equivalent boundary conditions we
obtain the Fourier-transform of the Hertz vector. It is demonstrated that the
ultra-relativistic bunch excites the surface waves, whereas the volume
radiation is absent. Fourier-transforms of the surface wave components and
spectral density of energy losses are obtained and analyzed.
