The Federal Aviation Administration (FAA) establishes the requirements for Emergency Locator Transmitters (ELTs) in aircraft registered in the United States. ELTs transmit on frequencies of either 121.5 MHz or 406.0 MHz. The purpose of the transmitters is to aid in the location of downed aircraft. Transmitters begin broadcasting upon impact.
The FAA requirements for ELTs are detailed in Federal Aviation Regulations (FARs) Part 91, sub-part 207. An ELT is required for any aircraft having more than one seat, with minor exception. Regulatory requirements for an ELT can be met with either a 121.5 MHz or 406.0 MHz transmitter.
Most aircraft in the United States are equipped with an ELT which broadcasts on a frequency of 121.5 MHz. The International Civil Aviation Organization (ICAO) has adopted an ELT standard of 406.0 MHz. Satellite monitoring of 121.5 MHz has ceased, so satellite location of downed aircraft is only possible for aircraft equipped with a 406.0 MHz ELT.
Pilots operating United States aircraft on international flights need to be aware of ELT requirements for the country they are flying into. Mexico and Canada, for example, both require aircraft operating in their airspace to be equipped with a 406.0 MHz ELT.
ELT Replacement Considerations
Aircraft owners should consider the type of flying they do to determine if the expense of upgrading to a 406.0 MHz ELT is warranted. Those operating in remote areas or planning international travel should consider upgrading to a 406.0 MHz ELT. Additionally, should an aircraft's ELT need replacement it would be wise to replace with a 406.0 MHz ELT for the additional safety and operational flexibility provided by the 406.0 MHz ELTs.