The Performance investigation of marine radar reflectors carried out by the defense research agency, Qinetiq in the aftermath of the loss of the 25ft yacht Ouzo last summer, has finally been published today.

Click here to download the MAIB / Qinetiq radar reflector report

The results, which were delayed due to consultations with radar reflector manufacturers can be summarized as follows:

*None of the nine units tested meets the the forthcoming draft ISO8729 [2] standard, which requires a 7.5 square-metre radar cross section (RCS) at angles of heel up to 20° for yachts, although one of the units was compliant to the angle stipulated for powerboats and catamarans of 10°

*Only one of the units tested claimed to be compliant with the existing standard ISO8729 – however, this performance was not recreated in the Qinetiq tests.

*Several of the units tested did conform with the current ISO8729, despite not holding ‘type-approval’.

What was Ouzo carrying?
Ouzo is known to have been carrying a ‘six-inch octahedral radar reflector’ although the MAIB report of 12 April does not state what make.

The MAIB report states: ‘Although any radar reflector is better than none, the type of reflector fitted to Ouzo can theoretically produce a reasonable peak increase in the RCS but, in practice, its overall performance is poor, and it is now evident that at best there was only a 50% probability that the ship would have been able to detect Ouzo on the radar at close range.’

The Qinetiq report states that short-range visibility (less than 2.6NM) of a radar reflector is very poor with an RCS of one metre squared. The current ISO8729 only requires 0.625 square metres RCS at all angles of heel up to 20°.

It continues: ‘For radar reflectors with an RCS of two square metres and above the probability of being tracked inside 2NM increases significantly’

Items on test
The report tested nine products ranging in price from £16 (Plastimo 16″) to £2,000 (POLARef 11) in a lab, simulating 16 knots of windspeed and swells of 5ft:

Plastimo 16″ Octahedral & 4″ tube
Davis Echomaster
Viking Tri-lens Large & Standard
Echomax 230
Firdell Blipper 210-7
Sea-Me
POLARef 11

The reflector height was 4m with the Bridgemaster radar scanner at 30m. The reflectors were tested for radar cross section (RCS) – measured in square metres – at angles of heel from 0° to 20°.