AIM 

4/20/23 

reaching a safe airport, or decide not to divert to the nearest safe airport, the escort aircraft is not obligated to 

continue and further escort is discretionary. The decision will depend on the circumstances of the individual 

incident. 

6

−

2

−

4.  Emergency Locator Transmitter (ELT) 

a.  General. 

1. 

ELTs are required for most General Aviation airplanes. 

REFERENCE

−

 

14 CFR SECTION 91.207. 

2. 

ELTs of various types were developed as a means of locating downed aircraft. These electronic, battery 

operated transmitters operate on one of three frequencies. These operating frequencies are 121.5 MHz, 243.0 

MHz, and the newer 406 MHz. ELTs operating on 121.5 MHz and 243.0 MHz are analog devices. The newer 

406 MHz ELT is a digital transmitter that can be encoded with the owner’s contact information or aircraft data. 

The latest 406 MHz ELT models can also be encoded with the aircraft’s position data which can help SAR forces 

locate the aircraft much more quickly after a crash. The 406 MHz ELTs also transmits a stronger signal when 

activated than the older 121.5 MHz ELTs. 

(a) 

The Federal Communications Commission (FCC) requires 406 MHz ELTs be registered with the 

National Oceanic and Atmospheric Administration (NOAA) as outlined in the ELTs documentation. The FAA’s 

406 MHz ELT Technical Standard Order (TSO) TSO

−

C126 also requires that each 406 MHz ELT be registered 

with NOAA. The reason is NOAA maintains the owner registration database for U.S. registered 406 MHz 

alerting devices, which includes ELTs. NOAA also operates the United States’ portion of the Cospas

−

Sarsat 

satellite distress alerting system designed to detect activated 406 MHz ELTs and other distress alerting devices. 

(b) 

As of 2009, the Cospas

−

Sarsat system terminated monitoring and reception of the 121.5 MHz and 

243.0 MHz frequencies.  What this means for pilots is that those aircraft with only 121.5 MHz or 243.0 MHz 

ELTs onboard will have to depend upon either a nearby air traffic control facility receiving the alert signal or an 

overflying aircraft monitoring 121.5 MHz or 243.0 MHz detecting the alert and advising ATC. 

(c) 

In the event that a properly registered 406 MHz ELT activates, the Cospas

−

Sarsat satellite system can 

decode the owner’s information and provide that data to the appropriate search and rescue (SAR) center. In the 

United States, NOAA provides the alert data to the appropriate U.S. Air Force Rescue Coordination Center 

(RCC) or U.S. Coast Guard Rescue Coordination Center. That RCC can then telephone or contact the owner to 

verify the status of the aircraft. If the aircraft is safely secured in a hangar, a costly ground or airborne search is 

avoided. In the case of an inadvertent 406 MHz ELT activation, the owner can deactivate the 406 MHz ELT. If 

the 406 MHz ELT equipped aircraft is being flown, the RCC can quickly activate a search. 406 MHz ELTs permit 

the Cospas

−

Sarsat satellite system to narrow the search area to a more confined area compared to that of a 121.5 

MHz or 243.0 MHz ELT. 406 MHz ELTs also include a low

−

power 121.5 MHz homing transmitter to aid 

searchers in finding the aircraft in the terminal search phase. 

(d) 

Each analog ELT emits a distinctive downward swept audio tone on 121.5 MHz and 243.0 MHz. 

(e) 

If “armed” and when subject to crash

−

generated forces, ELTs are designed to automatically activate 

and continuously emit their respective signals, analog or digital. The transmitters will operate continuously for 

at least 48 hours over a wide temperature range. A properly installed, maintained, and functioning ELT can 

expedite search and rescue operations and save lives if it survives the crash and is activated. 

(f) 

Pilots and their passengers should know how to activate the aircraft’s ELT if manual activation is 

required. They should also be able to verify the aircraft’s ELT is functioning and transmitting an alert after a crash 

or manual activation. 

(g) 

Because of the large number of 121.5 MHz ELT false alerts and the lack of a quick means of verifying 

the actual status of an activated 121.5 MHz or 243.0 MHz analog ELT through an owner registration database, 

U.S. SAR forces do not respond as quickly to initial 121.5/243.0 MHz ELT alerts as the SAR forces do to 406 

6

−

2

−

2 

Emergency Services Available to Pilots