HELRAS
HELRAS or the Helicopter Long Range Active Sonar is a naval helicopter undersea sensor, a dipping sonar, deployed by helicopters of many naval air forces around the world to detect submarines; it is a form of geophysical MASINT.
History
HELRAS was first developed in the 1970s by Bendix, FIAR and British Aerospace. Another rival system was called FLASH. In the 1980s, the system was supplied by Bendix.A competitor of HELRAS is the Low Frequency Active Sonar.