Underwater Locator Beacons

An underwater locator beacon (ULB), also known as an underwater locating device or underwater acoustic beacon, is a device affixed to aviation flight recorders such as the cockpit voice recorder, flight data recorder, and aircraft fuselage. The device activates by being immersed in water, at which point it is designed to emit an ultrasonic pulse of 37.5 kHz every second for a minimum of 30 days. ULBs attached to the airframe are called low frequency ULBs and transmit the pulse at 8.8 kHz. These devices are not only designed to survive accidents, but to remain fully functioning after impact. Research from 2011 determined that ULBs had a 90% survival rate over nearly thirty above-sea air accidents.

As of January 1, 2020, new European aviation safety regulations on air operations dictate that the transmission time of the ULBs attached to the flight recorders must be extended from 30 to 90 days. The same ruling dictates that large aircraft flying routes more than 180 nautical miles from a shore must be equipped with an additional low frequency ULB on the airframe. Low-frequency ULBs must comply with ETSO-C200 regulations or equivalent, and cannot be installed in the wings or empennage.

Low frequency ULBs have a very long detection range allowing them to provide effective assistance in reducing the time and cost of locating wreckage. They transmit an 8.8 kHz acoustic signal (ping) for at least 90 days and the low frequency provides an increased detection of 7-12 nautical miles, four times greater than the standard ULBs installed on flight data recorders and cockpit voice recorders. The maximum operational depth of a low frequency ULB is 20,000 feet and they can be activated by immersion in both salt and freshwater. The battery is a lithium single cell type with a service life of at least six years. The ULB assembly itself comprises the ULB DK180 Beacon, a mounting kit, and an adapter plate.

An aircraft maintenance program is needed to guarantee that procedures for testing the ULB, which is conducted concurrently with battery replacement, provide functional testing of the ULB before replacing the old battery to ensure that the device is still functioning properly. The maintenance program should consist of standard periodic maintenance, such as regular checking of the device operation as it pertains to manufacturer requirements, life limits on the battery of the ULB, and the cleaning of the switch contacts. When installing the ULB on the flight recorder, it is critical to make sure that the switch contacts are arranged such that they are not likely to contribute to the build-up of debris that could cause the contacts to inadvertently short. To do this, the contacts should be vertical or downward-facing.

The ULB is a crucial device in emergency situations. As such, it is best practice to ensure you are getting yours from a trusted source. For underwater locator beacons and much more, look no further than ASAP NSN Hub. Owned and operated by ASAP Semiconductor, we can help you find all types of parts for the aerospace, civil aviation, defense, electronics, industrial, and IT hardware markets. Our account managers are always available and ready to help you find all the parts and equipment you need, 24/7-365. For a competitive quote, email us at sales@asapnsnhub.com or call us at 1-920-785-6790. Let us show you why we consider ourselves the future of purchasing.


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April 30, 2021

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