3.7 Radio Silence Control (Seelonce Mayday, Seelonce Distress, Prudonce, Seelonce Feenee)

3.7 Radio Silence Control (Seelonce Mayday, Seelonce Distress, Prudonce, Seelonce Feenee)

During active Mayday distress operations, VHF Channel 16 must remain completely clear of non-distress communications. To maintain strict discipline and prevent interference with life-saving signals, the International Telecommunication Union (ITU) established specialized prowords derived from French. Mastering these radio silence control terms is a vital component of the RYA SRC curriculum.

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Prowords for Imposing Radio Silence

If unauthorized stations transmit routine traffic on Channel 16 while distress communications are taking place, radio silence can be commanded using specific ITU signals.

+------------------------------------------------------------------+
|                  RADIO SILENCE CONTROL PROWORDS                  |
+------------------------------------------------------------------+
| PROWORD          | SPOKEN AS       | AUTHORIZED TRANSMITTER      |
| ---------------- | --------------- | --------------------------  |
| SEELONCE MAYDAY  | See-lonse Mayday| Vessel in Distress ONLY     |
| SEELONCE DISTRESS| See-lonse Dist. | Controlling Coastguard / SAR|
| PRUDONCE         | Proo-donse      | Controlling Coastguard ONLY |
| SEELONCE FEENEE  | See-lonse Fay-ne| Controlling Coastguard / SAR|
+------------------------------------------------------------------+

1. SEELONCE MAYDAY

• Authority: Transmitted ONLY by the vessel in distress itself.
• Trigger: Used if an outside radio station interrupts the distress vessel's voice transmissions.
• Voice Format:

  MAYDAY [Name of Station Interrupting]
  THIS IS
  BLUE FIN
  SEELONCE MAYDAY
  OUT
  

2. SEELONCE DISTRESS

• Authority: Transmitted by the controlling Coastguard station (MRCC) or a vessel coordinating Search and Rescue (SAR) traffic on behalf of the Coastguard.
• Trigger: Used when unauthorized stations transmit non-distress traffic on Channel 16 during an active emergency.
• Voice Format:

  MAYDAY ALL STATIONS ALL STATIONS ALL STATIONS
  THIS IS
  SOLENT COASTGUARD SOLENT COASTGUARD SOLENT COASTGUARD
  SEELONCE DISTRESS
  OUT
  

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Restricted Working: PRUDONCE

As a distress situation matures, the controlling Coastguard station may reach a stage where total radio silence on Channel 16 is no longer essential, but distress traffic is still active.

• Signal: PRUDONCE (pronounced proo-donse, meaning caution/prudence).
• Effect: Signals that restricted working is permitted on Channel 16. Stations may use Channel 16 for urgent brief calls, provided transmissions are kept strictly short and do not interfere with ongoing SAR operations.
• Voice Format:

  MAYDAY ALL STATIONS ALL STATIONS ALL STATIONS
  THIS IS SOLENT COASTGUARD
  PRUDONCE
  OUT
  

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Termination of Radio Silence: SEELONCE FEENEE

When rescue operations are completed and distress traffic has ceased, the controlling station must formally announce the restoration of normal radio operations.

• Signal: SEELONCE FEENEE (or SILENCE FINI, pronounced see-lonse fay-nee).
• Effect: Restores Channel 16 to normal routine watchkeeping and calling procedures.
• Voice Format:

  MAYDAY
  ALL STATIONS ALL STATIONS ALL STATIONS
  THIS IS
  SOLENT COASTGUARD SOLENT COASTGUARD SOLENT COASTGUARD
  TIME ONE ONE THREE ZERO UTC
  BLUE FIN
  SEELONCE FEENEE
  OUT
  

Summary Table of Radio Silence Commands

The Necessity of Controlling Radio Silence During Emergencies

When a vessel transmits a Mayday call on VHF Channel 16, it is vital that the channel remains completely free of non-emergency transmissions. Uninvolved mariners who continue routine chatter, radio checks, or harbor logistics on Channel 16 during a distress situation can mask crucial search coordinates and jeopardize human life.

To maintain strict discipline, international maritime law empowers the casualty vessel and the controlling Coast Guard station to impose and manage radio silence on the distress frequency.

Mandatory Silence Prowords & Their Meanings

Four specific GMDSS prowords govern radio silence during distress operations:

1. SEELONCE MAYDAY (Imposed by Casualty Vessel):

   • Transmitted directly by the vessel in distress to silence an interfering radio station.
   • Example: "STATION CALLING, THIS IS SEA NYMPH - SEELONCE MAYDAY - OUT."

2. SEELONCE DISTRESS (Imposed by Controlling Coast Station / MRCC):

   • Transmitted by HM Coastguard or the station controlling distress traffic to enforce silence on all listening vessels.
   • Example: "ALL STATIONS, ALL STATIONS, THIS IS SOLENT COASTGUARD - SEELONCE DISTRESS - OUT."

3. PRUDONCE (Restricted Working Permitted):

   • Transmitted by the controlling coast station when the emergency phase of distress traffic has stabilized. It permits restricted, urgent communications on Channel 16, but full routine traffic remains prohibited.
   • Example: "ALL STATIONS, ALL STATIONS, THIS IS SOLENT COASTGUARD - PRUDONCE - OUT."

4. SEELONCE FEENEE (Distress Finished / Silence Lifted):

   • Transmitted exclusively by the controlling station when search and rescue operations are complete and full normal radio working is restored on Channel 16.
   • Example: "ALL STATIONS, ALL STATIONS, THIS IS SOLENT COASTGUARD - 1430 UTC - SEA NYMPH - SEELONCE FEENEE - OUT."

Station Obligations During Imposed Silence

When SEELONCE MAYDAY or SEELONCE DISTRESS is declared, all ship stations within radio range MUST:

• Immediately cease all transmissions on VHF Channel 16.
• Maintain a continuous listening watch on Channel 16 to monitor SAR updates.
• Record key coordinates and casualty updates in the onboard GMDSS radio logbook.
• Refrain from transmitting until PRUDONCE or SEELONCE FEENEE is broadcast by the controlling authority.