Reliability Study of ULB Devices Used in Aircrafts

FDR (Flight Data Recorder) and CVR (Cockpit Voice Recorder) devices, which are known as black boxes by the public, are very important for aviation. ULB(Underwater Locator Beacon) is an underwater sound projector which is activated by water immersion and it is attached to FDR and CVR in aviation use. If an aircraft is submerged in water after an air accident, ULB signal can be detected by hydrophones held by SAR teams and then underwater locations of the recorder devices will be calculated. Thus, wreckage and recorders can be found and investigations can be carried out to find out root causes of the accident. ULB devices could not be detected during search operations of some accidents occurred over the ocean in recent years. Authorities have been making some changes to ULB regulations which become a matter of debate in aviation community very often. In this study, possible causes of the unexpected low performance of ULB devices besides the effects originated by natural characteristics of the underwater acoustic environment, potential improvements of changes made by authorities, and existing other factors which may contribute to the problem were examined