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How it works: Underwater Locator Beacon (ULB)


The functioning of an underwater locator beacon (ULB) revolves around the utilization of acoustic signals. Let’s delve into the mechanics:

The activation of the Underwater Locator Beacon (ULB) occurs automatically when an aircraft equipped with a flight recorder (CVR or FDR) crashes into water.

The ULB generates a high-frequency sound wave, known as an ultrasonic pulse, at approximately 37.5 kHz ± 1 kHz. This pulse is transmitted through water and can be detected by individuals equipped with receivers designed for this purpose.

The process of search and locate involves utilizing vessels or aircraft that are equipped with underwater acoustic receivers to listen for the signal emitted by the ULB. Through the technique of triangulation, the exact location of the beacon can be determined.

The minimum transmission duration for ULBs is 90 days, ensuring that search and rescue teams have sufficient time to locate the wreckage. It is important to emphasize the crucial role these beacons play in enhancing survival rates in air accidents that occur over bodies of water.

The underwater locator beacon (ULB), which is alternatively referred to as an underwater locating device (ULD) or underwater acoustic beacon, consists of various essential components.

Transducer: The electrical signals are transformed into acoustic pulses by the transducer. To enable the transmission of the acoustic pulse, the battery provides power to the ULB.

Hydrophone: The hydrophone, an underwater microphone with exceptional sensitivity, is capable of detecting and converting the ultrasonic signals emitted by the beacon into electrical signals.

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