science

Underwater locator beacon

Underwater locator beacon is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Underwater locator beacon rather than just read about it. In short: An underwater locator beacon (ULB), underwater locating device (ULD), or underwater acoustic beacon is a device that emits an acoustic pulse intended to guide searchers equipped with a suitable receiver to the location of the beacon underwater. Application An underwater locator beacon is fitted to aviation flight recorders such as the cockpit voice recorder (CVR) and flight data recorder (FDR).

Key takeaways

Underwater locator beacon belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Underwater locator beacon to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Underwater locator beacon from memory before moving on to harder problems.

Reference excerpt

An underwater locator beacon (ULB), underwater locating device (ULD), or underwater acoustic beacon is a device that emits an acoustic pulse intended to guide searchers equipped with a suitable receiver to the location of the beacon underwater.

Application An underwater locator beacon is fitted to aviation flight recorders such as the cockpit voice recorder (CVR) and flight data recorder (FDR). ULBs are also sometimes required to be attached directly to an aircraft fuselage. These ULBs are triggered by water immersion; most emit an ultrasonic 10 ms pulse once per second at 37.5 kHz ± 1 kHz. Research by the French Bureau d'Enquêtes et d'Analyses pour la Sécurité de l'Aviation Civile (BEA) has shown that it has had a 90% survival rate spanning 27 air accidents over the sea. The ULBs fitted in Air France Flight 447, which crashed on 1 June 2009, were certified to transmit at 37.5 kHz for a minimum of 30 days at a temperature of 4 °C. After investigating the crash, the BEA recommended that FDR ULBs' transmission period be increased to 90 days and for "airplanes performing public transport flights over maritime areas to be equipped with an additional ULB capable of transmitting on a frequency (for example between 8.5 kHz and 9.5 kHz) and for a duration adapted to the pre-localisation of wreckage" (i.e. with increased range). On ships built on or after 1 July 2014, underwater locating devices must ensure a regulatory transmission time of at least 90 days. The European Union Aviation Safety Agency requires since 1 January 2019 for most large aeroplanes operated over routes that go farther than 180 nautical miles (330 km; 210 mi) from a shore to be equipped with an additional ULB emitting at 8.8 KHz. It also requires since 1 January 2020 that the transmission time be increased to 90 days.

Power source and activation A beacon is typically supplied with electrical power by a lithium battery, which needs to be replaced after several years. Once the beacon becomes immersed in water, a built-in "water switch" activates it via the water's presence completing an electrical circuit, and the beacon starts emitting its "pings"; the battery power should be sufficient for 30 to 40 days after the activation. The minimum battery voltage is 2.97 volts and the maximum is 3.5 volts.

The National Transportation Safety Board reported a case in 1988, involving an Aerospatiale AS-355F-1 helicopter, when the water switch had accidentally activated during the aircraft's normal operation; as a result, the battery power had been exhausted by the time the accident happened, and the beacon was not emitting the acoustic signal when it needed to do so.

Maximum detection range A 37.5 kHz (SPL of 160.5 dB re 1 μPa) pinger can be detectable from the surface from a distance of 1–2 kilometres (0.62–1.24 mi) in normal conditions and 4–5 kilometres (2.5–3.1 mi) under ideal conditions. A 8.8 KHz pinger can be detectable from a distance of 13–22 kilometres (8.1–13.7 mi) or four times the distance of standard ULBs.

See also SOFAR bomb Towed pinger locator Underwater acoustics Sonar Emergency locator beacon

References

External links

DK120 Underwater Acoustic Beacon Underwater Locator Beacon detection ranges for fuselage encapsulated recorders (FAA 1968 study)

Illustrations

Worked examples

Example 1 — a first encounter with Underwater locator beacon

Start with the simplest possible case. Write down what Underwater locator beacon claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Underwater locator beacon before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Underwater locator beacon ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Underwater locator beacon

In research: Underwater locator beacon appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Underwater locator beacon in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Underwater locator beacon is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aircraft emergency systems, Beacons, so understanding it makes those chapters shorter.
In everyday life: Look for Underwater locator beacon outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Underwater locator beacon in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Underwater locator beacon means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Underwater locator beacon out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Underwater locator beacon in simple terms?

Why does Underwater locator beacon matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Underwater locator beacon?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Underwater locator beacon.