Abstract: Cylindrical arrays are widely used in omnidirectional or very wide sector sonars. These arrays utilise horizontal phasing for compensation of geometrical phase-delays, which form a narrow beam. The cylindrical symmetry of the array provides beam rotation around the array. The ahead looking sonar using the above method needs an array with a large number of staves and a larger number of receiver channels. This paper presents the design approach to ahead looking sonars with a cylindrical arc array using delay of the staves signals for equalising of the array and a beamforming processor for beam steering. This sonar performance is determined by array parameters and a processing method used to form the beams. There is no simple closed form of mathematical expression for a delayed signals and steered beam of such arrays so the array and method of beamforming have to be analysed by considering the elements spacing, weighting and directivity. The angular aperture and radius of array curvature are analysed. The results of a computer simulation of beam patterns for such sonars are presented. The indication for design of ahead looking sonars with cylindrical arc array using equalising and beam steering processing are presented.