Emergency Locator Transmitter


Radar Service for VFR Aircraft in Difficulty:

  • Radar equipped ATC facilities can provide radar assistance and navigation service (vectors) to VFR aircraft in difficulty when the pilot can talk with the controller, and the aircraft is within radar coverage. Pilots should clearly understand that authorization to proceed in accordance with such radar navigational assistance does not constitute authorization for the pilot to violate CFRs. In effect, assistance is provided on the basis that navigational guidance information is advisory in nature, and the responsibility for flying the aircraft safely remains with the pilot
  • Experience has shown that many pilots who are not qualified for instrument flight cannot maintain control of their aircraft when they encounter clouds or other reduced visibility conditions. In many cases, the controller will not know whether flight into instrument conditions will result from ATC instructions. To avoid possible hazards resulting from being vectored into IFR conditions, a pilot in difficulty should keep the controller advised of the current weather conditions being encountered and the weather along the course ahead and observe the following:
    • If a course of action is available which will permit flight and a safe landing in VFR weather conditions, non-instrument rated pilots should choose the VFR condition rather than requesting a vector or approach that will take them into IFR weather conditions; or
    • If continued flight in VFR conditions is not possible, the non-instrument rated pilot should so advise the controller and indicating the lack of an instrument rating, declare a distress condition; or
    • If the pilot is instrument rated and current, and the aircraft is instrument equipped, the pilot should so indicate by requesting an IFR flight clearance. Assistance will then be provided on the basis that the aircraft can operate safely in IFR weather conditions

Transponder Emergency Operation:

  • When a distress or urgency condition is encountered, the pilot of an aircraft with a coded radar beacon transponder, who desires to alert a ground radar facility, should squawk Mode 3/A, Code 7700/Emergency and Mode C altitude reporting and then immediately establish communications with the ATC facility
  • Radar facilities are equipped so that Code 7700 normally triggers an alarm or special indicator at all control positions. Pilots should understand that they might not be within a radar coverage area. Therefore, they should continue squawking Code 7700 and establish radio communications as soon as possible

  • Battery operated transponders react to forces (detecting a crash) and should operate for 48 hours continuously
  • Transmit on 121.5 and 243 MHz (guard) and the newer 406 MHz
    • 121.5/243 MHz are analog devices while 406 MHz is a digital transmitter encoded with owners contact and aircraft data; can transmit aircraft position and transmits a much stronger signal
    • 406 transmitters must be registered with NOAA
  • Pilots should be able to activate and deactivate the ELT manually for testing or in the event of an emergency when they have failed to activate autonomously


  • ELTs are required to be tested every year
  • ELTs should be tested in accordance with the manufacturer's instructions, preferably in a shielded or screened room or specially designed test container to prevent the broadcast of signals which could trigger a false alert
  • When this cannot be done, aircraft operational testing is authorized as follows:
    • Analog 121.5/243 MHz ELTs should only be tested during the first 5 minutes after any hour. If operational tests must be made outside of this period, 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 are not authorized

Emergency Locator Transmitter Testing Instructions Example
Figure 1: Emergency Locator Transmitter Testing Instructions Example

False Signals:

  • Caution should be exercised to prevent the inadvertent activation of ELTs in the air or while they are being handled on the ground. Accidental or unauthorized activation will generate an emergency signal that cannot be distinguished from the real thing, leading 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
  • A false ELT signal could be confusing and interfere with a real emergency, usually the result of aerobatics, hard landings, movement, and maintenance
  • Can be minimized by monitoring guard:
    • In-flight, when able
    • Before engine shutdown
    • When the ELT is handled during installation or maintenance
    • When maintenance is being performed near the ELT
    • When the aircraft is moved
    • When a signal is heard:
      • Turn off the ELT and determine the problem
      • If it has been activated, notify ATC of the inadvertent activation
      • Maintenance may be required before the switch is moved back to armed

Inflight Monitoring and Reporting

  • Pilots are encouraged to monitor 121.5 MHz and/or 243.0 MHz while inflight to assist in identifying possible emergency ELT transmissions
  • If a signal is detected, report to the nearest facility:
    • Location the signal was first and last heard
    • Position of maximum strength
    • Flight altitudes and frequency on which the emergency signal was heard: 121.5 MHz or 243.0 MHz. If possible, positions should be given relative to a navigation aid. If the aircraft has homing equipment, provide the bearing to the emergency signal with each reported position

No person may operate a U.S. Registered civil airplane unless:

  • There is attached to the airplane, an approved automatic type ELT in operable condition
  • Except after June 21, 1995, an ELT that meets the requirements of TSO-C91 may not be used for new installations (see FAR 91.207 for more)
  • Must be attached in such a way that the transmitter is not likely to be damaged in a crash, as far aft as possible
  • Batteries must be replaced if the ELT has run more than an hour (cumulative) or 50% of its useful life
  • The ELT itself must be inspected within 12 calendar months after the last inspection (see FAR for inspection items)


  • Ferry a newly acquired airplane from the place where possession of it was taken to a place where the ELT transmitter is to be installed
  • Ferry an airplane with an inoperative ELT from a place where repairs cannot be made to a place where they can
  • No other people than the required crew may be carrier aboard a ferried airplane
  • Does not apply to turbo-jets before January 1, 2004
  • Aircraft engaged in schedule flights by scheduled air carriers
  • Aircraft while engaged in training operations conducted within 50 NM radius of the airport
  • Aircraft engaged in flight operations incident to design and testing
  • Aircraft certified by the Administrator for research and development purposes
  • Aircraft while used for showing compliance with regulations, crew training, exhibition, air racing, or market surveys
  • Aircraft equipped to carry not more than 1 person
  • Any aircraft with the ELT removed must be placarded with the date of removal, make, model, serial number, and reason for removal
  • No person may operate more than 90 days after the ELT is initially removed
  • On and after January 1, 2004, aircraft with a maximum payload capacity of more than 18,000lbs when not used for air transportation


  • ELTs are required for most General Aviation aircraft
  • Manufacturers of ELTs are required to mark the expiration date of the battery, based on 50 percent of the useful life (or for rechargeable batteries at 50 percent of their useful life of charge) on the outside of the transmitter
    • Batteries are required to be changed on that date or when the transmitter has been in use for more than 1 cumulative hour