Underwater locator beacon signal propagation on tropical waters

Abstract

In the last 12 years, about 16 crashes involving commercial aircraft have ended in sea-crashes and dozens of maritime accidents resulting in sunken vessels occur every year. At the instant the aircraft Flight Data Recorder (FDR), or the ship Voyage Data Recorder (VDR), comes in contact with water, a locating device called ULB (Underwater Locator Beacon) starts a continuous emission of acoustic signals, or pings, for a minimum period of 30 days. After the crash of the Air France 447, in 2009, a discussion began about the effectiveness of the pingers in assisting in the location of “black boxes” and whether they should undergo some kind of modification to improve its capabilities. In order to understand the propagation of the pulses emitted by the ULBs in regions of past accidents, two fundamental aspects of the irradiated signal quality are analyzed: the components and specifications of pingers used in “black boxes” – as for example the acoustic intensity and the emitted waveform shape – and the physical characteristics of the medium and in what form it influences in the transmission of the pulses during its propagation by the ocean. This work has as main objective to contribute to the quantification of the detection capability of ULBs emitted pings in different scenarios /configurations and hopefully being able to clarify major issues regarding ULBs signal propagation assisting in the improvement of search and rescue (SAR) operational methodologies and in the development of “black box” acoustic signals detection instruments.