Procedure word

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"WILCO" redirects here. For other uses, see Wilco (disambiguation).

Procedure words or prowords are words or phrases limited to radio telephone procedure used to facilitate communication by conveying information in a condensed standard form.[1]

Universal prowords[edit]

Affirm, Affirmative[edit]

"Confirm" or "Yes", used in Aviation. Some air arms of military forces also use a "double click" sent over the radios by keying the mic twice to produce a "--" like Morse code, this is usually used when the pilot is unable to talk due to heavy workload or stress.


In amateur radio transmissions, the transmitting station's call sign followed by the word "clear" is used to indicated the sending station is done transmitting and leaving the airways, alias turning off the radio.


"No" or "NEG". Because over a poor quality connection the words "affirmative" and "negative" can be mistaken for one another (for example over a sound-powered telephone circuit), United States Navy instruction omits the use of either as prowords.[2] Sailors are instructed to instead use "yes" and "no".


"This is the end of my transmission to you and no answer is required or expected."


"This is the end of my transmission to you and a response is necessary. Go Ahead: transmit."

Contrary to popular belief, "Over" and "Out" are never used at the same time, since their meanings are mutually exclusive. Therefore "Over and Out" should never be used together in radio communications. Historically, the term "Over and Out" was used to mean "Over to you, and when you're done, I'm Out." With spring-loaded PTT buttons on modern combined transceivers, the same meaning can be communicated with just "Out", as in "Ops, Alpha, ETA five minutes. Out."

Roger, Received, Romeo, Copy[edit]

"I have received your last transmission satisfactorily, radio check is loud and clear." "Roger" is used occasionally to mean "yes", but this is incorrect. The proper proword for "yes" is "Affirm".

Romeo, although incorrect, has the same meaning, but is used mainly in Australian Maritime Operations. Use of the correct prowords "Roger" or "Received" should be encouraged.

For Maritime VHF, Copy does not mean the same as Roger or Received. It is used when communications between 2 other stations which includes information for your station that has been overheard and received satisfactorily.


"I have received your initial call; send me your message."


"I understand and will comply (WILL COMPLY = WILCO)." To be used only by the addressee.

Note that "ROGER" and "WILCO" used together are redundant, since WILCO includes the acknowledgement of ROGER.[3]

Maritime/Amateur VHF prowords[edit]

Radio Check[edit]

What is my signal strength and readability; how do you hear me?

5 by 5 is an older term used to assess radio signals, as in 5 out of 5 units for signal strength and for readability. Other terms similar to 5x5 are "loud and clear" or "Lima and Charlie". Example:


US Army correct check:


If the initiating station (ALPHA 12 in the example) cannot hear the responding station (X-RAY 23 above), then the initiator attempts a radio-check again, or if the responder's signal was not heard, the initiator replies to the responder with "NEGATIVE CONTACT, ALPHA 12 OUT".

The following readability scale is used: 1 = Bad (unreadable); 2 = Poor (readable now and then); 3 = Fair (readable but with difficulty); 4 = Good (readable); 5 = Excellent (perfectly readable).

Read Back for Check[edit]

Instruction to receiving station to read back the information it has received for confirmation. Same as HOW COPY. Reply from receiving station will be preceded by I READ BACK or I COPY, confirmation by transmitting station takes the form of the proword CORRECT or GOOD COPY. See example 2, below. The U.S. Army uses "HOW COPY" only.

Say Again[edit]

"I have not understood your message, please say again". Usually used with prowords ALL AFTER or ALL BEFORE. Example: radio working between Solent Coastguard and a motor vessel, call-sign EG 93, where part of the initial transmission is unintelligible

- All stations, all stations, this is Solent Coastguard, Solent Coastguard. Be advised large shipping vessel entering Southampton Water, currently at position ...[transmission unintelligible]...Out.

- Solent Coastguard, Solent Coastguard, this is Echo Golf Niner Three. Say again all after position. Over.

At this juncture, Solent Coastguard would reply, giving the position of the shipping vessel preceded with the prowords I SAY AGAIN:

- All stations, All stations, this is Solent Coastguard. I say again, large shipping vessel entering Southampton water, currently at position one decimal two miles from Calshot Spit on bearing one six five degrees. Vessel restricted in ability to deviate from its course. Do not impede. Out.

Note that the word "REPEAT" is never to be used in place of SAY AGAIN, except in aviation, where pilots say "Please say again" or "please repeat". (It's just a short-cut instead of saying "please repeat") especially in the vicinity of naval or other firing ranges, as REPEAT is an artillery proword with a wholly different meaning. However, REPEAT may be used in the middle of a signal to emphasise information Example:

EG93: Victor Juliet Five-Zero, this is Echo Golf Niner-Three. How much fuel do you require? Over.
VJ50: Echo Golf Niner-Three, this is Victor Juliet Five-Zero. I require six five - repeat six five - litres of diesel. Over.
Or alternatively:
VJ50: Echo Golf Niner-Three, this is Victor Juliet Five-Zero. I require six five litres of diesel. Repeat six five litres. Repeat diesel. Over

However, given the above stricture on using 'REPEAT', it is better to use 'I SAY AGAIN' or 'WORDS TWICE' or 'FIGURES TWICE', as in:

VJ50: Echo Golf Niner-Three, this is Victor Juliet Five-Zero. I require six five litres of diesel. I say again six five litres of diesel. Over

Station Calling[edit]

This proword is used when addressing an unidentified station which has just hailed the receiver. For example, Cowes VTS has received a transmission from an unidentified station. The correct reply would be:

"Station calling Cowes VTS, Station calling Cowes VTS - this is Cowes VTS. Over."

This Is[edit]

This transmission is from the station whose designator immediately follows. For clarity, the station called should be named before the station calling. So, "Mike Juliet Zero, THIS IS Golf Whiskey Three..." or for brevity, "Mike Juliet Zero, Golf Whiskey Three, ROGER and OUT". Never "This is GW3 calling MJ0" or any other reversed combination.

So Far[edit]

During transmission with lots of information, this proword can be used between transmissions, to ensure all information is passed on correctly.

Example of Radio Communications Using Procedure Words[edit]

Example 1[edit]

2 helicopters are flying in formation, Indian 610 and Indian 613:

Indian 610: "613, I have a visual on you at my 3 o'clock. 610"
Indian 613: "Roger. 613"
Indian 610: "613, Turn right to a heading of 090. 610"
Indian 613: "Wilco. 613"

Anytime a radio call is made (excepting 'standby' where the correct response is silence), there is some kind of response indicating that the original call was heard. 613's "Roger" confirms to 610 that the information was heard. In the second radio call from 610, direction was given. 613's "Wilco" means "Will Comply."

It is better procedure, however, to always read back an instruction. For example, if all 613 says is "Wilco," 610 is not certain that he correctly heard the heading as 090. If 613 replies with a read back and the word Wilco ("Turn Right zero-niner-zero, Wilco") then 610 knows that the heading was correctly understood, and that 613 intends to comply, which is a safer situation.

Example 2[edit]

The following is the example of working between two stations, EG93 and VJ50 demonstrating how to confirm information:

EG93: "Victor Juliet Five-Zero, Victor Juliet Five-Zero, this is Echo Golf Niner-Three. Request rendezvous at 51 degrees 37.0N, 001 degrees 49.5W. Read back for check. Over."
VJ50: "Echo Golf Niner-Three, Echo Golf Niner-Three, this is Victor Juliet Five-Zero. I read back: five one degrees three seven decimal zero North, zero zero one degrees four niner decimal five West. Over."
EG93: "Victor Juliet Five-Zero, Victor Juliet Five-Zero, this is Echo Golf Niner-Three. Correct. Out."

Distress, Urgency and Safety prowords (used for maritime and aeronautical VHF)[edit]

MAYDAY (distress)[edit]

I, my vessel or a person aboard my vessel is in grave and imminent danger, send immediate assistance. This call takes priority over all other calls.

The correct format for a Mayday call is as follows:

[The first part of the signal is known as the call]
"Mayday, Mayday, Mayday,

This is (vessel name repeated three times, followed by call sign if available)

[The subsequent part of the signal is known as the message]

Mayday (vessel name)

My position is (position as a LAT-LONG position or bearing and distance from a fixed point)

I am (type of distress, e.g. on fire and sinking)

I require immediate assistance

I have (number of people on board and their condition)

(Any other information e.g. "I am abandoning to life rafts")


VHF instructors, specifically those working for the Royal Yachting Association, often suggest the mnemonic MIPDANIO for learning the message of a mayday signal: Mayday, Identify, Position, Distress, Assistance, Number of crew, Information, Over.

In aviation a different format is used:

[First part of the message] MAYDAY, MAYDAY, MAYDAY

[Second part of the message] Callsign is stated at the end, followed by either "Heavy" or "Super", though this is not always necessary

[Third part of the message] Nature of the emergency

For example: MAYDAY MAYDAY MAYDAY, Air Transat 236 heavy, we have lost both of our engines, due to fuel starvation, we are gliding now.

After that pilot can give, or the controller can ask for, additional information, such as, fuel and number of passengers on board.

Pan Pan (urgency)[edit]

Main article: Pan-pan

(pronounced /ˈpæn ˈpæn/)[4]

I, my vessel or a person aboard my vessel requires assistance but is not in distress. This overrides all but a MAYDAY call, and is used, as an example, for calling for medical assistance or if the station has no means of propulsion. The correct call is:


All stations, all stations, all stations

This is [vessel name repeated three times]

My position is [position as a LAT-LONG position or bearing and distance from a fixed point]

I am [type of urgency, e.g. drifting without power in a shipping lane]

I require [type of assistance required]

[Any other information e.g. size of vessel, which may be important for towing]


Securité (safety)[edit]

pronounced /sˈkjʊərɨt/ say-KEWR-i-tay

I have important meteorological, navigational or safety information to pass on. This call is normally broadcast on a defined channel (channel 16 for maritime VHF) and then moved onto another channel to pass the message. Example:

[On channel 16]


All stations, all stations, all stations.

This is Echo Golf Niner-Three, Echo Golf Niner-Three, Echo Golf Niner-Three.

For urgent navigational warning, listen on channel six-seven.


[Then on channel 67]


All stations, all stations, all stations.

This is Echo Golf Niner-Tree (three), Echo Golf Niner-Tree, Echo Golf Niner-Tree.

Floating debris sighted off Calshot Spit.

Considered a danger to surface navigation.


Out of use[edit]

  • Charlie charlie (confirmed, correct), still used in Africa by French pilots

See also[edit]


  1. ^ [1]
  2. ^ Thomas J. Cutler (2009). The Bluejacket's Manual, United States Navy 24th Edition. Annapolis: Naval Institute Press. p. 497, et seq. ISBN 1-59114-153-2. 
  3. ^ ACP 125(F), Communication Instructions Radiotelephone Procedure, Combined Communication Electronics Board (published 5 September 2001), September 2001, pp. 3–14, retrieved 2012-02-20 
  4. ^ Tim Bartlett (2009). VHF handbook. Southampton: The Royal Yachting Association. p. 52. ISBN 978-1-905104-03-1.