Failures and Emergencies — Page 115, Lesson 101

I want to walk you through the procedures that govern radio communications during failures and emergencies. This is a critical area because when an aircraft is in distress, the entire radio discipline changes to protect that aircraft and the people trying to help it. Let's start with the imposition of silence. The station that is in distress, or the station that is controlling the distress traffic, has the authority to impose silence. This means they can order everyone else to stop transmitting. They can do this either to all stations in the mobile service within the area, or they can target a specific station that is interfering with the distress traffic. The instruction will be addressed "to all stations" or to just one station, depending on the situation. In either case, the exact phrase they use is 'STOP TRANSMITTING'. This is not a casual request — it is a command backed by international regulation. And importantly, the radio distress signal 'MAYDAY' is reserved exclusively for the aircraft in distress and for the station that is controlling the distress traffic. No one else may use it. Now let's look at action by all other stations. Distress communications have absolute priority over every other type of communication. If you are aware that distress traffic is happening on a frequency, you must not transmit on that frequency unless one of four specific conditions is met: 1. The distress is cancelled, or the distress traffic is terminated. 2. All distress traffic has been transferred to other frequencies. 3. The station controlling communications gives you permission. 4. You yourself have to render assistance — meaning you are in a position to help the aircraft in distress. If you are aware of distress traffic but cannot assist the aircraft in distress, you must still continue listening to that traffic. You keep listening until it becomes evident that assistance is actually being provided. You don't just switch off and go about your business — you monitor until help is clearly on the way. Now let's move to termination of distress communications and of silence. When an aircraft is no longer in distress, it must transmit a message cancelling the distress condition. That's the aircraft's responsibility. Then, the station that has been controlling the distress communication traffic — once it becomes aware that the distress condition is ended — must take immediate action. It must make this information available as soon as possible to two parties: - The ATS unit concerned — that's Air Traffic Services. - The aircraft operating agency concerned, or its representative, in accordance with pre-established arrangements. Finally, the distress communication and silence conditions are formally terminated by transmitting a message that includes the words "DISTRESS TRAFFIC ENDED". This message is sent on the frequency or frequencies being used for the distress traffic. And here's an important point: this message can only be originated by the station controlling the communications. And they can only do it when, after receiving the message cancelling the distress condition, they are authorized to do so by the appropriate authority. So there's a chain: the distressed aircraft cancels, the controlling station gets authorization, and only then does the controlling station broadcast "DISTRESS TRAFFIC ENDED" to release everyone from silence. That covers the core emergency communication procedures — who can impose silence, how other stations must behave, and how the distress condition is formally ended.