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New technology will help locate aircraft underwater

Jan 9, 2015

This post is also available in: עברית (Hebrew)

Almost every passenger aircraft carries emergency locator transmitters (ELT). All aircrafts are required to carry a minimum of one ELT. Larger passenger jets, carry one or more additional ELTs.

In case the aircraft sinks in the ocean like in the recent AirAsia accident, these are not efficient.

ELTs emit two radio signals: 121.5 megahertz and 406 megahertz. The 121.5 megahertz is currently being phased out. The newer 406 megahertz signal is used so the planes can be found more quickly

According to Government Security News, one problem with AirAsia Flight 8501 (and Malaysia Flight 370 presumably), is that they landed in the water. Neither aircraft had a breakaway ELT that has the ability to float once an aircraft impacts water.

If an aircraft submerges quickly, its ELT signal is seriously impacted by water, especially salt water. Like ELTs, transponders, which emit an identifying signal in response to an interrogating received signal, are also on board each aircraft.

The transponders display the plane’s altitude, direction of flight, ground speed, and any altitude change. Still, planes such as Flight 370 continue to go un-located.

A new air traffic surveillance system is being implemented in many countries to help find lost aircraft, however. By the year 2020, all U.S. based planes will be required to have Automatic Dependent Surveillance – Broadcast (ADS-B) on board. ADS-B would allow each aircraft to broadcast its GPS position along with other information like heading, ground track, ground speed, and altitude. Receivers on the ground then receive this information and send it to air traffic control displays.

The ADS-B information can be used to augment existing primary and secondary (transponder-based) radar or used in lieu of those radar technologies. It could locate planes whether they are in traditional flight paths or not, and also possibly pinpoint where the aircraft struck the water. The EU is requiring that all planes implement this technology by 2017; it is mandatory in Australia now.