Why Airplane Black Boxes Don’t Use GPS in the Ocean

When a commercial airliner crashes into the ocean, how do rescuers find it? Standard radio frequencies and GPS simply do not work underwater.

Instead, flight data recorders rely on a brilliant piece of aerospace engineering: the Underwater Locator Beacon (ULB). Known in aviation as a "Pinger," this highly durable metal cylinder activates only when its sensor touches water and completes an electrical circuit. Once triggered, it doesn't emit radio waves; it emits a powerful acoustic pulse at exactly 37.5 kilohertz.

This specific ultrasonic frequency was chosen so sonar systems can hear it over the natural noise of the ocean. Built to survive the crushing pressure of the abyss at 20,000 feet, modern aviation standards now require these beacons to pulse continuously for 90 days, echoing through the darkness to guide recovery teams.

Did you know black boxes used sound instead of radio waves? Let us know below!