Should We Keep 121.5 Alive?


Photo: CC BY-SA 3.0

Pilots are trained to use the radio frequency 121.5 in the event of an emergency. Emergency locator transmitters (ELTs) broadcast over 121.5 to notify search and rescue of a downed aircraft. FAA radio facilities, Civil Air Patrol, and often pilots monitor 121.5 as a way to receive distress signals. So why does the FCC, and subsequently the FAA and NTSB, want to ban something simple that could potentially save lives?

The answer lies in the advancement of modern technology – the increased use of the more accurate satellite-based 406 MHz ELT, and the decision of major search and rescue company COSPAS-SARSAT to cease monitoring 121.5 in 2009. But does the introduction of a more reliable system mean that everyone should be required to use it? And should we go so far as to ban the use of an emergency frequency so commonly known to help pilots?

Since 1973, the FAA has required almost all aircraft to have an emergency locator transmitter (ELT) on board. ELTs are small transmitters that emit a signal and provide a way for search and rescue (SAR) to locate a downed airplane, increasing the survival odds for a pilot and passengers. They can transmit on either 121. MHz or 406.025 MHz. It’s commonly known that the 406 MHz ELTs are much more accurate, but a good portion of the general aviation fleet still uses 121.5 MHz ELTs.

121.5 ELTs
Many ELTs commonly used in aviation are designed to transmit an analog signal over the frequency 121.5 when activated, allowing anyone that is monitoring the frequency to hear the distress signal and notify appropriate search and rescue teams. These 121.5 ELTs are inexpensive and simple to use, but they aren’t without their problems.

If an ELT is in the ‘armed’ mode, it will become activated during a crash and transmit a noisy alarm over the frequency 121.5. But sometimes a hard landing will set it off, or it can be accidentally activated during ground operations. More often than not, ELTs are activated in non-emergency situations, and ATC and operators spend a lot of time tracking down false ELT signals. In addition, finding the signal requires homing in to the strength of the signal – a difficult and inaccurate task when the signal accuracy is only limited to about 10 miles.

406 MHz
A 406 MHz ELT transmit a digital signal, which allows for a code to be transmitted along with the distress signal. This code has details about the aircraft, including its registration number and a point of contact.

406 MHz ELTs are more accurate, pinpointing the location of a downed aircraft to within one to three miles, decreasing the potential search area drastically from the of a 121.5 transmitter. And false alerts are less of a problem with 406 MHz ELTs, too, meaning authorities can act immediately upon receipt of a distress signal, instead of spending their time trying to determine if it’s a fake signal or not.

Why Ban 121.5?
It’s easy to see why the 406 MHz ELT is better. What’s less obvious is why we should ban the use of 121.5

The NTSB thinks that the use or 406 MHz ELTs should be mandated. In a 2007 Safety Recommendation letter, the NTSB described the downfall of 121.5 emergency locator transmitters and recommended that the FAA mandate the installation and use of 406 MHz transmitters in all aircraft before major search and rescue organizations COSPAS-SARSAT ceased its monitoring. They NTSB believes that without a mandate, pilots will refuse to upgrade to the 406 MHz units, making it more difficult on search and rescue and possibly creating undue risk.

The FAA agrees, but finds it more difficult to mandate. The Aircraft Owners and Pilots Association has stood strong against the 121.5 ban, saying that it’s too costly for the approximately 200,000 general aviation pilots to upgrade, and that the decision regarding which ELT to use should rest with the pilots themselves.

In the meantime, the FCC is also considering a ban on 121.5 ELTs. In 2013, they opened up a comment period regarding the banning of 121.5 ELTs, and again AOPA opposed in this letter, stating that the FCC needs to leave aviation safety matters to the FAA. It remains to be known if the ban will come into play, but pilots should expect it to happen eventually, and more importantly, for their own safety, pilots should probably just upgrade to the 406 MHz ELT of they haven’t already.

Could - or should - the ban of 121.5 ELTs mean the death of the 121.5 frequency altogether? After all, the frequency is used for more than just ELTs. It’s an emergency frequency in which a pilot can declare an emergency, and it’s still monitiored by FAA facilities, Flight service stations and the civil air patrol. And many pilots still monitor it, which can be helpful to other pilots and ATC if they do hear something on that frequency. And pilots are taught to switch to 121.5 if they’re intercepted for some reason, such as inadvertent flight through a prohibited area.

What do you think? Should we just accept that new technology is better than the old and move on? Or should we fight to keep 121.5 alive?