Over the last week we have all been reading about the Sanchi, the Iranian Oil Tanker now on the bottom of the East China Sea. 32 lives have been lost and there is a substantial environmental impact of the 1m barrels of crude condensate spilt or burnt.
Yesterday we read in the FT that the vessel tracking services noted that the Sanchi’s AIS appears to have been switched off for almost 24 hours before the collision with the Chinese grain carrier 160 miles off the mouth of the Yangtze River. This could have been a maintenance issue with the AIS unit or its power supply, or issues with satellite communications, but we were disappointed to read that it is not uncommon for vessels to disappear from the AIS tracking, potentially related to the use of the open AIS to track vessel movements to assist in sanctions breaking, or simply to not contribute to commodity price speculation.
Whilst sailors of smaller vessels in UK waters are less likely to encounter sanctions busting, or dark-running tankers to or from Milford Haven, it is important to note that AIS is no substitute for good watch keeping and radar monitoring. The FT reports that it is not unusual for tankers departing the Turkish port of Ceyhan to disappear from AIS before making deliveries or taking part in ship to ship transfers. We’ll bear this in mind when planning our Greek and Turkish water cruising for the late summer.
What is AIS?
Automatic Identification System (AIS) is a standard for each vessel to broadcast its name, location, speed and course to other vessels. When receiving this information it gives a vessel a view of marine traffic in their vicinity and allows them to be ‘seen’ by that marine traffic. Each vessel requires a dedicated VHF AIS transceiver that typically allows local traffic to be viewed on a AIS enabled chart plotter. All AIS transceivers are limited to the VHF range, typically about 10–20 nautical miles, if the AIS aerial is mounted at about 15m above sea level. Offshore it is possible to use satellite to relay AIS messages, with Satellite-AIS (S-AIS) technology.
AIS was widely introduced after a 2002 IMO SOLAS requirement for almost all vessels over 300 tons on international voyages to fit a ‘Class A’ AIS Transceiver. In 2006 a Class B specification was agreed and simpler lower cost units have subsequently become available for all vessels. In 2013 the Royal Ocean Racing Club (RORC) made the fitting and operation of AIS a requirement for all yachts competing in RORC races.
It is worth noting that during RORC races it is not unknown for yachts to track their competitors’ tactics ‘over the horizon’ using the AIS information.