Abstract: The article presents the practical aspects of a modernisation effort involving two on-board systems in Navy helicopters used for detecting and anti-submarine warfare, i.e. a sonobuoy-based system and an on-board sonar. The advantages of using digital signal processing in both systems are discussed as well as the advantages of advanced methods for visual representation of the noise picked up and the results of sounding. A description is given of the display systems before and after the modernisation.