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Rescue by Digital Tether

New personal digital transponders greatly improve man-over-board recovery. From our "Safety Gear" from our January 2008 issue

April 7, 2008
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Raymarine LifeTag

Courtesy Of Raymarine

Whether zipping along at 30 knots on a Volvo 70, bashing to Bermuda at nine, or plodding north on Lake Michigan in light air, racing offshore is a risky business. A common cause of death for offshore racers is drowning as a result of falling overboard, and as we’ve seen all too many times, safety harnesses are underutilized. Today, thanks to satellites, radio beacons, and GPS technology, there are several sure-fire ways of recovering overboard crew quickly.

Inshore recovery
The most basic, and relatively inexpensive way, to track a man overboard is with what are known as”closed-loop,”;”locally managed overboard response,” or “proximity” systems, which activate when a person equipped with an electronic transmitter leaves the system’s coverage area, or when the transmitter goes underwater. Raymarine’s LifeTag device is an example. The LifeTag “Starter” system, which retails for $685, is composed of two LifeTags, which have Lithium batteries with a lifetime of 2,000 hours, wrist straps, an alarm module, a base station, and a power cable.

|| |—| | Courtesy of Raymarine| |Raymarine’s LifeTags send a signal to Raymarine plotters when a wearer goes overboard. The location is then displayed on the plotter’s screen. Even if you don’t have a Raymarine plotter, an alarm will sound.| The LifeTag system integrates into Raymarine’s SeaTalk network, so crew-overboard data-specifically the position of the boat when the system is activated-is sent to all onboard Raymarine chartplotters and displays. Even if you don’t have a Raymarine electronics suite, an audible alarm will sound if a pendant goes out of range (about 30 feet). Position data won’t be input until someone physically activates the man overboard button on whatever plotter or GPS they’re using (often denoted as MOB on a GPS receiver), but at least there’s a warning that someone’s gone missing. The system accommodates up to 16 LifeTags, and additional base stations can be added to the network.

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Other closed-loop systems include, Wavefinder, Sea Marshall and ACR’s Vecta 2, but unlike the LifeTag, these three system’s wearable transmitters send location information to receivers that display either a visual or aural indication of the bearing and distance to the missing crewmember. These three systems use the 121.5-megahertz frequency, which is useful, because even though it’s being phased out, many rescue assets, such as U.S. Coast Guard vessels, won’t be decommissioning their 121.5-megahetz receivers all that quickly. Personal Locater Beacons operating on that frequency will still work if a nearby vessel is equipped with a direction finder tuned to 121.5 megahertz. That, of course, in effect takes the rescue out of the hands of various satellite-dependant rescue organizations, and dumps it firmly in the lap of the vessel’s crew, especially after 2009. For raceboats, especially ones with shorthanded crews, having PLBs equipped with both 406- and 121.5-megahertz transmitters better the odds of rescue.

|| |—| | Courtesy of Manufacturer| |The FastFind Plus, by McMurdo/Pains Wessex transmits on 121.5 and 406 megahertz, and has an integral GPS for faster fixes by rescue organization| Raymarine’s LifeTag uses ZigBee, a standards-based wireless network system that supports low data rates, low power consumption, and reliability. Think about it as an updated version of Bluetooth RF technology.

Satellite-based recovery
After 2009, the countries that make up the International Satellite System For Search and Rescue, the international COSPAS-SARSAT constellation of rescue satellites will no longer receive 121.5-megahertz distress calls. The replacement frequency, 406 megahertz, is far superior in many ways, especially because it can transmit more data (including position data, if the sending unit is equipped with a GPS receiver) and at a higher power (5 watts versus the 121.5-megahertz devices’ one-tenth watt.

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Personal 406-megahertz systems are essentially Emergency Position Indicating Rescue Beacons, meant for use by individual crew. When activated manually or through immersion, they immediately transmit data on the 406-megahertz frequency, which will be picked up by the COSPAS-SARSAT [COSPAS is an acronym for the Russian words Cosmicheskaya Sistyema Poiska Avariynich Sudov, which translates to Space System for the Search of Vessels in Distress.

SARSAT is an acronym for Search And Rescue Satellite-Aided Tracking, see www.cospas-sarsat.org for more information] constellation anywhere between 70 degrees north and south latitudes, and usually within 45 minutes, depending on what satellites are overhead. Since these devices must be registered, it’s easy for one of the 45 ground stations and 23 mission control centers worldwide that serve as search and rescue points of contact to determine whether or not the distress signal is valid by speaking with the people or organization the individual EPIRB is linked with. If you want rapid response to your distress signal, remember to register your EPIRB as soon as you buy it-and quickly direct search-and-rescue assets to the scene. In comparison to 121.5-megahertz beacons, which are known for false alerts, the 406-megahertz systems generate few false alarms.

These newer satellite-based systems provide precise position data of the overboard crew, and it’s constantly updated by the transmitting device, as long as its battery has power and the transmitter is still being worn. Usually the satellite will provide rescuers with a position on the first satellite pass that will be accurate to within one to three nautical miles. If the 406-megahertz beacon is equipped with a GPS receiver, accuracy improves to about 300 feet.

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|| |—| | Courtesy of Manufacturer| |ACR’s ResQFix personal locater beacon is small (1.25″ x 5.81″ x 2.31″), and light (10.4 oz., including flotation pouch), and has a battery life of over 24 hours.| Companies that produce 406-megahertz beacons include ACR, which offers three units, the AquaFix Digital 406 GPS I ($549.99), which can receive data from a handheld GPS through an optical cable, the AquaFix Digital 406 GPS I/O ($649.99), which includes a GPS receiver, and the ACR ResQFix 406 GPS ($799), which at 1.4”x 5.85” x 2.21” and 9.8 ounces, may be the smallest full-featured PLB on the market. Pains Wessex/McMurdo offers the FastFind 406 PLB EPIRB ($649), which doesn’t have an internal GPS, and the FastFind 406 Plus ($995), which does.

Of the two types of systems-the 121.5-megahertz and the 406-megahertz-racers venturing into blue water should probably go for the personal EPIRBs, and invest in units with internal GPS receivers. If coastal races are more your style, the closed-loop system should be sufficient. Neither system replaces a proper, full-size, GPS-equipped EPIRB for your boat, especially where battery life is concerned. A full-size EPIRB/GPIRB has a battery life of at least 48 hours as opposed to the best PLB, which has a battery life of a little more than 24 hours. Offshore racers might also consider taking a PLB in their ditch bag as a backup for their EPIRB.

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