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AIM 

6/17/21 

discretionary. The decision will depend on the 
circumstances of the individual incident. 

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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 Commis-

sion (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

gen-

erated 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 MHz ELT alerts. 
Compared to the almost instantaneous detection of a 
406 MHz ELT, SAR forces’ normal practice is to wait 
for confirmation of an overdue aircraft or similar 
notification. In some cases, this confirmation process 

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Emergency Services Available to Pilots