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Emergency Locator Transmitters (ELTs)Emergency Locator Transmitters (ELTs)


On February 1, 2009, the international COSPAS-SARSAT satellite system discontinued satellite-based monitoring of the 121.5/243-MHz frequencies, in part because of a high number of false signals attributed with these frequencies. While there's no requirement in the United States to replace the first- and second-generation 121.5-MHz ELTs, since that date, 121.5/243-MHz distress signals transmitted from ELTs operating on the lower frequency are only detected by ground-based receivers such as local airport facilities and air traffic control facilities or by overflying aircraft. It is important to note that existing 121.5-MHz ELTs, although still legal from the FAA's perspective, provide very limited assistance if an aircraft crashes, especially in a remote location.

AOPA opposes any attempt to mandate or otherwise require the replacement of existing 121.5/243-MHz ELTs with 406-MHz units. AOPA recognizes the benefits that can be derived from the advanced ELTs available today. However, the benefits of advanced ELTs must be balanced against cost and the needs of the individual aircraft owner. AOPA supports the installation of these more advanced ELTs on a voluntary basis.

As always, feel free to call AOPA's Pilot Information Center at 800/USA-AOPA with questions.


ELTs are emergency transmitters that are carried aboard most general aviation aircraft in the U.S. In the event of an aircraft accident, these devices are designed to transmit a distress signal on 121.5, 243.0-megahertz frequencies (and for newer ELTs, on 406 MHz). Currently, ELTs are required to be installed in almost all U.S.-registered civil aircraft, including general aviation aircraft, as a result of a congressional mandate. The ELT hibernates in the tailcone of most general aviation aircraft. The danger of its "out-of-sight, out-of-mind" location is the possibility of missing an inspection that may alert the pilot of a potential malfunction.

Although most general aviation aircraft must have an attached operable emergency ELT, aircraft engaged in training operations conducted entirely within 50 nm of the departure airport are a notable exceptions. Other exceptions applicable to Part 91 operations are single-seat aircraft, flight testing, aerial applications, and ferrying flights.  FAR Part 91.207 lists all exceptions.

ELTs must be inspected once every 12 calendar months for:

  • Proper installation;
  • Battery corrosion;
  • Operation of the controls and crash sensor; and
  • The presence of a sufficient signal radiated from its antenna.

Technical Information


The batteries must be replaced or recharged:

  • When the transmitter has been in use for more than 1 cumulative hour; or
  • When 50 percent of their useful life (or for rechargeable batteries, 50 percent of their useful life or charge) has expired, as established by the transmitter manufacturer under its approval.

Removing the ELT

Pilots generally realize that an aircraft can be operated for up to 90 days with the ELT removed if a placard is displayed. We still see some violations in this area because of the following:

  • Although the operator/pilot can change an ELT battery under FAR Part 43, Preventive Maintenance (more on this later), to remove the ELT or to leave the battery out requires an A&P logbook endorsement (weight and balance considerations), including the date of initial removal, make and model and serial number of the unit, the reason for ELT removal, and the placard in view of the pilot.
  • A ferry flight to a location where a repair could be made is allowed, but only if a repair could not be made at the departure location. Pilots have gotten into trouble on this when they flew either without having their mechanic complete the above process or flew after the 90 days.

ELT maintenance

Concerning ELT maintenance endorsements, battery life, and pilot-in-command responsibility:

  • A 1994 regulation change, 91.207(d), requires a separate sign-off or annual inspection for the ELT. The mechanic actually makes a separate log entry about the ELT. This usually will occur at the same time of the aircraft's annual inspection, but it doesn't have to. The unwary pilot in command could miss the timing on this inspection and find himself in the same trouble as if he had flown with an airworthiness directive compliance time missed. As we know, the mechanic's signature at an annual is a statement of condition at that time and does not guarantee that everything will remain airworthy until the next annual.
  • Following directly from the above discussion, the unwary pilot can also miss the ELT battery replacement date. This is the "half-life" or FAR-prescribed replacement date, but very often this does not correspond with the timing of the annual inspection. It is the pilot in command's responsibility to know the replacement date; some owners will replace the battery early to coordinate it with the annual inspection. As mentioned, the pilot/operator can replace an ELT battery under preventive maintenance, FAR 43. This only holds true, however, for a battery with plug-in or snap-on connector replacement, one where no soldering is required. The pilot performing this work has the same responsibility as a mechanic to make a log entry for the work and the new battery date, as well as perform a simple function test after the new battery is installed. This test should constitute simply turning on the unit with the toggle switch and listening on a com radio on 121.5 MHz for three sweeps of tone. For obvious reasons, regulations prescribe this to be done only at five minutes after the hour and only after coordination with any FAA control tower within line-of-site distance. Note: This simple pilot function test does not meet the G-switch/signal-strength test that a mechanic must perform and endorse annually.