Learning Center Library Contents

Down Arrow
Welcome Guest
Aviation Learning Center Document Radio Communications Phraseology and Techniques - P-8740-47
Author: Federal Aviation Administration Date: revised April 2006
used for alignment
used for alignment
Viewing Options: View Document as Chapters Chaptersused for alignment View Full Document Full Documentused for alignment View Print-Friendly Document Printer Friendlyused for alignment Search Inside this Document Search Insideused for alignment

< Previous Chapter used for alignment Next Chapter > used for alignment

Emergency Locator Transmitter (ELT)
used for alignment


Emergency Locator Transmitters (ELTs) are required for most general aviation airplanes (14 CFR 91.52). ELTs of various types have been developed as a means of locating downed aircraft. These electronic, battery-operated transmitters emit a distinctive downward sweep audio tone on 121.5 MHz and 243.0 MHz. If "armed" and subjected to crash forces, they are designed to automatically activate and continuously emit these signals. The transmitters will operate continuously for at least 48 hours over a wide temperature range. A properly installed and maintained ELT can expedite search and rescue operations and save lives.


ELTs should be tested in accordance with the manufacturer's instructions, preferably in a shielded or screened room to prevent the broadcast of signals which could trigger a false alert. When this kind of testing cannot be done, aircraft operational testing is authorized on 121.5 MHz and 243.0 MHz as follows.

  • Tests should be conducted only during the first five minutes after any hour. If operational tests must be made outside of this timeframe, they should be coordinated with the nearest FAA Control Tower or FSS.
  • Tests should be no longer than three audible sweeps.
  • If the antenna is removable, a dummy load should be substituted during test procedures.
  • Airborne tests of the ELT are not authorized.

False Alarms

Use caution should to prevent the inadvertent activation of your ELT in the air or while it is handled on the ground. Accidental or unauthorized activation will generate an emergency signal that cannot be distinguished from the real thing, which could lead to expensive and frustrating searches. A false ELT signal could also interfere with genuine emergency transmissions and hinder or prevent the timely location of crash sites. Frequent false alarms could also result in complacency and decrease the vigorous reaction that must be attached to all ELT signals.

Numerous cases of inadvertent activation have occurred as a result of aerobatics, hard landings, movement by ground crews, and aircraft maintenance. These false alarms can be minimized by monitoring 121.5 MHz and/or 243.0 MHz as follows.

  • Prior to engine shut down at the end of each flight.
  • When the ELT is handled during installation or maintenance.
  • When maintenance is being performed in the vicinity of the ELT.
  • When the aircraft is moved by a ground crew.

If you hear an ELT signal, turn off the ELT to determine if it is transmitting. If it has been activated, maintenance might be required before the unit is returned to the "ARMED" position.

Inflight Monitoring

While you are flying, you might want to use your second radio (if installed) to monitor 121.5 MHz and/or 243.0 MHz to assist in identifying possible emergency ELT transmissions. If you hear an ELT signal, report the following information to the nearest air traffic facility.

  • Your position at the time the signal was first heard.
  • Your position at the time the signal was last heard.
  • Your position at maximum signal strength.
  • Your flight altitudes and frequency on which the emergency signal was heard - 121.5 MHz or 243.0 MHz.

If possible, give these positions relative to a navigation aid. If the aircraft has homing equipment, provide the bearing to the emergency signal with each reported position.

Search and Rescue Satellite (SARSAT)

Search and rescue is a lifesaving service provided through the combined efforts of the federal agencies signatory to the national search and rescue plan, and the agencies responsible for search and rescue in each state. Operational resources are provided by the US Coast Guard, Department of Defense components, the Civil Air Patrol, the Coast Guard Auxiliary, state, county, and local law enforcement and other public safety agencies.

The introduction of the SARSAT system enhances the effectiveness of search and rescue. SARSAT also amplifies the importance of ensuring that your ELT remains silent, except for authorized testing or in an actual emergency. Search and rescue missions launched because of a false ELT signal are costly and unnecessary. Search and rescue services include search for missing aircraft, survival aid, rescue, and emergency medical help for the occupants after an accident site is located.

used for alignment