Technology helps locate and rescue mariners who fall overboard

The risk of falling overboard hasn’t changed much in the 6,000 years since humans first used a log to float across a river, but the technology to mitigate it has come a long way. Man-overboard (MOB) systems can alert the crew immediately if someone falls in, and many can help locate them in the water.

How each system achieves these goals — and to what extent — varies. Typically they involve a wearable transmitter that signals the vessel when someone has gone over the rail. Different designs work with vessels and crews of all sizes, from simple alerts with engine kill switches for single-sailor recreational boats to complex systems that integrate with a ship’s navigation systems to help keep watch over an entire crew.

Worn strapped to the arm, Raymarine’s LifeTag maintains a wireless signal with a base station on the vessel. When that signal is degraded, either by distance or water, the base station sounds an audible alarm, which can also be triggered manually.

When integrated with Raymarine SeaTalk networks, LifeTag can also provide audible and visual alerts to all stations, record the GPS position of the MOB event and mark it as a target waypoint on all connected devices, and lower the range scale on connected chartplotter and radar displays to heighten visibility.

With FirstLight Solutions’ Mermaid ID, crewmembers wear an ID-pod that transmits a digital coded sonar signal upon contact with the water. When a through-hull hydrophone “hears” the signal, it tags the MOB impact point on an internal GPS, raises visual and audible alarms and uses an LED direction finder to guide the vessel.

At the other end of the scale is Mobilarm’s Crewsafe system, which relies on a series of wireless internal and external routers to create a monitoring and reporting network on board a vessel, an oil rig or a loading wharf. The system is scalable by adding routers, and can be integrated with existing navigation systems and GPS to automatically log a waypoint to mark an MOB incident.

Each crewmember carries a Crewsafe Tag, or transceiver, which broadcasts a unique radio signal via the routers. If the tag disconnects from the network for more than a few seconds, an alarm is triggered. Crew can also raise the alarm by pushing a duress button on the tag. Mobilarm also makes the MOBi-lert closed-loop overboard alert system for smaller vessels and crews.

Because they spend so much time on ladders to board vessels, marine pilots are a good fit for MOB gear.

Florida’s Tampa Bay Pilots Association began using the ORCA system manufactured by Virginia-based

BriarTek last year.

In the event of submersion, the transmitter signals all ORCA receivers within range and lights up with an integrated strobe light for visibility in the water. Some models, like the ORCA TX-104, broadcasts location and identification information, and can be tracked by any search and rescue assets using radio direction finders.

Trackable distance depends on antenna height and weather conditions, but has been tested effectively at a distance as great as 18 nautical miles. Capt. Terry Jednaszewski said the Tampa Bay Pilots found that antenna placement is crucial.

“Basically, there’s a receiver on

the pilot boat,” he said. “The receiver’s got a circular dial with LEDs around it. It gives a relative bearing to the signal.”

Chris Bernard

By Professional Mariner Staff