This is an idea that has been in my
head for some time and a few recent
MOB threads has prompted me to put the following forward again. The post is long but hopefully worth reading!
Although rare, we all realize that a
MOB is an extremely serious occurrence. I believe the most difficult aspect is locating and then returning to the person in the
water. Sure all the other aspects are serious but unless the person is located and the vessel brought to them, the chances for survival are very very slim. Even if the MOB is witnessed in the moment, keeping them in sight is very difficult, especially when short handed and doing a reverse track search for a MOB event that wasn't noticed in the moment is hardly likely to be successful.
There are a variety of electronic MOB
alarm systems available and they have their pros and cons but I have yet to see a off the shelf
concept as described below.
This
concept relies on the MOB carrying (and activating) a
GPS PLB. These are common enough, small enough and cheap(ish). Of course they alert a distant SAR / RCC but they could also alert the parent vessel and provide a
GPS position if the following was available.
Consider an onboard 406 MHz receiver that received the PLB
transmission, decoded the GPS position and thus both raised the
alarm and provided a accurate GPS location of the MOB to say the chart plotter.
Technically it would require an omnidirectional 406 MHz
antenna (say a vertical dipole), a receiver (either broadbanded over the several PLB channels or using a fast scanning technique), a decoder for the positional data contained the PLB
transmission, convert this to say
NMEA position and also a voice readout of the lat. and lon. Perhaps a 121.5 MHz receiver as well for demodulating the audio sweep alarm and connecting that to an audio alarm speaker.
All this technology exists and most of it (if not all) is in the public domain so it just takes someone smarter than me to pt it together in one package. It could be housed in a small waterproof module at the base of the
antenna and the only
wiring would be
power, an audio output to a speaker mounted anywhere and a RS 232
serial bus to the nav instrumentation. It would need to mounted as high as possible.
Current draw would be quite low until triggered.
Price could kept reasonable if say such receivers were mandated on off shore
racing fleets as economies of scale would kick in.
The range would not be great but I would expect it to be better than say 5 nm radius of the antenna. This means that if the MOB is within 5 nm of the antenna, there would be an audile alarm, a voice readout of the lat/lon and a MOB waypoint on the
chartplotter. As the 406 transmission is radiated every minute, it would really only need to receive one bust to
work and give the location.
This has to be a lot better than a stressed mark 1 eyeball scanning the
water from
deck height.
Yes it does mean the on
deck crew must wear the PLB and be able to use it but that is not a real hardship. Inshore, it is probable the parent vessel would locate the MOB before the local SAR assets could be mobilized and
offshore it would allow the parent vessel to be an effective primary independent SAR asset.
Someone will now post a link to an existing similar system
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