Mayday, Mayday! All About Aircraft Emergency Radio Frequencies

Mayday calls are made by pilots in life-threatening situations to alert nearby air traffic controllers that they may need assistance using aircraft emergency radio frequencies broadcast across the world.

Have you ever wanted to learn more about the technology behind these calls? I’m the expert here.

I’ll discuss the main aircraft emergency radio frequencies and how they’re used, including monitoring. I’ll also explain the mayday call as used in aircraft emergency communications.

Understanding Aircraft Emergency Radio Frequencies

Radio control tower for hearing mayday calls against a dramatic dark blue sky
Aircrafts use guard frequencies to communicate distress.

An aircraft emergency frequency, also known as a guard frequency, is an aircraft radio frequency reserved for emergency communications when in distress.

The use of the name “guard,” as you might have guessed, means these frequencies are guarded and reserved within the aircraft operations band exclusively for making distress calls and other emergency communications.

Misusing them can lead to punishment. The Federal Aviation Administration prohibits superfluous communications and false distress calls.

Those who misuse these rules are subject to fines of up to $144,344. It’s quite a hefty punishment!

Pilots who want to communicate air-to-air are encouraged to use 122.750 MHz to avoid interrupting the guarded aircraft emergency radio frequencies.

Emergency Radio Frequencies Used in Aviation

There are three main aircraft emergency radio frequencies in use today.

Very High Frequency (VHF) 121.5 MHz

Very high frequencies are within the range of 30 and 300 MHz.

Besides being used in aircraft emergencies based on the specific bands, VHFs are also used in DAB radios.

VHF 121.5 MHz, also known as the international air distress (IAD), is a guarded emergency radio frequency used in aeronautical space. It’s reserved for civilian aircraft, and pilots refer to it as guard.

VHF 121.5 MHz is monitored by Air Traffic Control (ATC) towers all over the world. In the US, the frequency is further monitored by the FSS service and national air traffic control centers.

The frequency is monitored in the UK by the Royal Air Force Distress and Division Cells (D&D).

VHF 121.5 MHz is primarily used in aircraft for distress signaling in emergencies. These emergencies include engine failures, equipment malfunctions, or other scenarios where there is a risk to life or property.

According to the FAA, air traffic facilities are required to have both transmit and receive capabilities for this emergency frequency.

For an air traffic controller to communicate with an aircraft equipped with VHF 121.5 MHz frequency, the pilot must have initiated the call and monitored the frequency.

On the other hand, if an aircraft wants to alert an ATC or another aircraft of an emergency, the ATC or the other aircraft must be monitoring the 121.5 MHz frequency.

Here is a video to help you visualize how the 121.5 MHz frequency is used during aircraft emergencies:

[Plane Crash Emergency Relay – ALWAYS Monitor 121.5]

Ultra High-Frequency (UHF) 243.0MHz

Also known as military air distress (MAD) or UHF guard, the ultra-high frequency band is used exclusively by military aircraft for making emergency calls.

This frequency operates slightly differently compared to its VHF 121.5 MHz counterpart.

When an aircraft or an ATC transmits on UHF 243.0MHz, the transmission overrides other UHF frequencies. All UHF radios around the transmission region will hear that one transmission.

406 MHz – COSPAS-SARSAT Distress Frequency

Besides the guard frequencies, 406 MHz is a third aircraft emergency radio frequency, used mostly by the latest emergency locator transmitters (ELTs).

ELTs are self-contained radio transmitters found on most general aviation aircraft. They’re activated by substantial impacts along the aircraft’s longitudinal axis.

ELTs came into use in 1973 after being mandated by Congress. This was after a small chartered aircraft carrying Nick Begich and US Representative Hale Boggs got lost, never to be found to date.

A satellite constellation (COSPAS-SARSAT ) was deployed in 1985 to determine whether an aircraft is down or not. This is used in locating aircraft.

A distress beacon signal transmitted on 406 MHz is received by the COSPAS-SARSAT system and processed for further action.

406 MHz ELTs have digital transmitters encoded with crucial contact information and aircraft data like position coordinates. This information is used by search and rescue (SAR) teams to locate and assist the aircraft in distress.

Moreover, 406 MHz ELTs transmit a stronger signal with a much higher accuracy when activated to locate the aircraft quickly after a crash.

Mayday Calls

Plane wing in a fixed position flying over the clouds against an orange sunset
Mayday calls use the VHF frequency for civilian aircraft and UHF for military planes.

Have you ever seen an airplane movie where the pilot yells Mayday! Mayday! on the radio? This common scenario in movies and TV shows actually happens in real life.

mayday call is an urgent signal used in emergency scenarios when there is a risk to life or property. It’s derived from the French word M’aidez, meaning “help me.”

The mayday call is made over VHF 121.5 MHz for civil aircraft and comprises three repeated mentions of Mayday, followed by the aircraft identification, position, and nature of distress.

The same applies to military aircraft, only that they transmit on UHF 243.0 MHz.

For example, “Mayday! Mayday! Mayday! This is ABC123, six zero miles east of Krishna at two seven two five Koru, Engine failure.”

After sending a mayday call, pilots should continue monitoring the frequency for response and instructions from ATC. Other aircraft in the area may also respond to offer assistance if possible.

Meanwhile, upon receiving a distress mayday call, ATC swings into action to coordinate emergency response.

The ATC alerts nearby aircraft of the emergency to alter their routes or avoid the affected region.

Also, rescue services like fire trucks, ambulances, and the police unit are alerted to respond.

If the plane crashes, SAR forces use the ELT radio frequency (406 MHz) to locate and assist the downed airplane.

Why Is 121.5 MHz Aircraft Emergency Frequency So Special?

It’s constantly monitored by all ATCs, that’s why!

When an airplane loses communication with the ATC (NORDO), 121.5 MHz is used to restore the communication.

In case of an emergency, the pilot switches to 121.5 MHz radio frequency and transmits a Mayday call.

The ATC then acknowledges the transmission and offers instructions on how to handle the situation.

Moreover, 121.5 MHz is strictly for emergency use only. Therefore, it’s not congested with other transmissions like air traffic control communications or aircraft-to-aircraft communications.

Reserving this frequency for emergency transmissions ensures that these calls are not missed or interfered with, increasing the chances of swift response and assistance during critical situations.

Wrong Frequency Selection

What do you think happens when the pilot selects the wrong frequency?

After all, different frequencies are assigned to aircraft based on their missions, among other considerations.

However, the flight crew must consult ATC before changing the frequency assigned during the previous flight.

If the aircraft goes out of range with the previous controlling station, there is the possibility of the flight crew selecting the wrong frequency. This results in the loss of communication.

Final Thoughts

I hope this article has been informative and has shed light on the different emergency radio frequencies used in aviation.

Remember, these are essential frequencies that can help save lives in emergencies.

The parting shot—if you’re a pilot, familiarize yourself with these frequencies and know when and how to use them properly.

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