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Watchkeeping safety - use of VHF radio and AIS 

MCA re-issues MGN 324 on the role of VHF radio and AIS for collision avoidance

The recent re-issue of MGN 324 by the MCA on the role of VHF radio and AIS for collision avoidance comes as a timely reminder of their appropriate and correct use, particularly with regard to collision avoidance.

Use of VHF to Aid Collision Avoidance

The International Maritime Organization (IMO) and the wider maritime community it represents has frequently commented on the misuse of VHF channels, especially Channel 16 and the channels used for port operations, ship movement and reporting. Although VHF makes an important contribution to navigation safety, its misuse can cause interference and become a danger to safety at sea.

IMO Member Governments have therefore unanimously agreed to ensure that VHF channels are used appropriately and correctly.

MGN 324 reminds us all that use of marine VHF on United Kingdom vessels and all other vessels in UK territorial waters and harbours may only be used in accordance with the ITU Radio Regulations. These Regulations specifically prescribe that:

• Channel 16 may only be used for distress, urgency, brief safety communications, and to establish voice communications which should then be transferred to a suitable working channel;

• Channel 70 may only be used for Digital Selective Calling, not voice communication;

• The only messages permitted on VHF channels allocated to port operations or ship movement services are those relating to the movement and safety of ships and to the safety of persons;

• All conversations must be preceded by identification, e.g. vessel name or call sign;

• The use VHF radio must be controlled by an operator holding a certificate issued or recognised by the station’s controlling Administration.

In spite of this, there have been an increasing number of collisions where subsequent investigations have found that at some stage before impact, one or both parties were using VHF radio in an attempt to avoid collision.

Serious consequences

Uncertainties can arise over the identification of vessels or a misunderstanding due to language difficulties. An imprecise or ambiguously expressed message could have serious consequences.

Valuable time can be wasted whilst mariners on vessels approaching each other try to make contact on VHF radio instead of paying attention to the lookout and complying with the International Regulations for Preventing Collisions at Sea, 1972 (COLREG).

Any attempt to use VHF to agree the manner of passing is fraught with the danger of misunderstanding and a course of action that does not comply with the COLREG may lead to the collision it was intended to prevent. COLREG should remain uppermost means of avoiding collision.

Use of Automatic Identification System (AIS)

AIS has the potential to make a significant contribution to safety, however, AIS information should always be treated with caution. Not all ships or marine craft carry or are required to carry AIS and in particular, leisure craft, fishing vessels and warships might not be fitted with AIS.

Watchkeepers should also be aware that AIS fitted on other vessels might be transmitting incorrect data due to input errors which may in turn lead to misleading information being displayed. Under certain circumstances, AIS may be switched off at the master's discretion and AIS positions derived from another vessel’s GNSS receiver (usually GPS) may not coincide with its exact positon. For that reason the information provided by AIS may not give a complete or correct "picture" of shipping traffic in your vicinity.

For these reasons, use of AIS should NOT be considered to replace the need for a visual lookout. There is no explicit provision in the COLREG for use of AIS information, therefore decisions should be taken based primarily on systematic visual and/or radar observations; collision avoidance must be carried out in strict compliance with the COLREG.

AIS target data will only be based on the target vessels’ course and speed over ground whilst for COLREG compliance such data must be based on the vessels’ course and speed through the water. Finally over reliance on AIS information may well breach COLREG Rule 7(c) in that assumptions shall not be made on the basis of scanty information.

For more guidance and support

The RYA Safety Advisory Notices and safety hub provide a substantial amount of information on the importance of keeping a good look out and the correct use of VHF, distress beacons and AIS.

Take advantage of a SPECIAL BUNDLE DISCOUNT of 25% when you buy both the print and eBook versions of the RYA International Regulations for Preventing Collisions at Sea. RYA members receive a further 15% discount on the bundle price when they add both items to the same basket.

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