Following a QinetiQ study commissioned by MAIB as a result of the loss of the yacht Ouzo the MCA has issued a Marine Guidance Note
MGN 349 (M+F) on the Carriage and Use of Radar Reflectors on Small Vessels.
The MCA strongly recommends that:
4.1 The requirements of SOLAS Chapter V Regulation 19 are complied with;
4.2 Yachtsmen permanently install, not just carry on-board, a radar reflector or Radar Target Enhancer (RTE) that offers the largest Radar Cross Section (RCS) practicable for their vessel;
4.3 Small craft owners and operators are strongly recommended to fit the best performing radar reflector possible. It is also essential for skippers to be aware that, notwithstanding the type of radar reflector fitted, in certain circumstances their craft may still not be readily visible on ships’ radars. They should navigate with caution.
The QinetiQ report contains comparative data on eight radar reflectors and one radar target enhancer. This can be accessed from the RYA website.
A graph in figure 1 of this report shows the effects of the clutter field as the highly variable response to each target RCS in the region up to 4nm. This is actually caused by both clutter and multipath.
The modelling shows that when using a radar reflector with an Radar Cross Section (RCS) of 1m2, 50% probability of detection is only achieved between 2.6 and 3.1nm and again between 4.6 to 9.1nm. More importantly it clearly illustrates the beneficial effects of increased RCS and consistency of return, particularly at close range. For radar reflectors with an RCS of 2m2 and above the probability of being tracked inside 2nm increases significantly. With a radar reflector of RCS of at least 4m2 50% probability of detection is achieved beyond 10nm from 4.5nm.
(Note from OCC Web editor: In discussion on this subject at the Conference of Yacht Cruising Clubs, it was pointed out that the RTE available to yachtsmen in the UK, The Sea-Me, will only operate at X-Band and will offer no performance at S-Band. Commercial Shipping, while in theory keeping watch on both X and S Bands, tends to rely on S band when away from coastal waters!)
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