Sonobuoy History from a UK Perspective
RAE Farnborough's Role in Airborne Anti-Submarine Warfare

A sonobuoy is a sophisticated underwater device capable of detecting and locating the source of underwater sounds. Sonobuoys -short for sonar-buoy- are relatively small expendable sonar systems that are dropped from military aircraft performing anti-submarine warfare.

The buoys are ejected from aircraft/helicopters in canisters and deploy upon water impact. An inflatable surface float with a radio transmitter rises to the surface for communication with the aircraft, while hydrophone(s) sensors and stabilizing equipment descend below the surface to a depth that is variable depending on the environmental conditions.

The buoy relays acoustic information from its hydrophone(s) via radio to operators on board the aircraft. Sonobuoys were developed in World War 2 with the aim of providing allied ASW aircraft with the ability to detect submerged U- boats who were trying to attack Allied convoys.