Martek Marine (UK) has launched its Crewtrack® man overboard (MOB) alarm/locator system saying it is the most effective on the market with a mechanism to prevent false alarms.
Martek highlights the importance of MOB alert equipment by citing a case where a Maltese ship did not realise they had lost a man until 0700 after the previous time he had been seen was the evening before at 1900 hours. Helicopters and planes were called out but the search was fruitless as the 'casualty' was found onboard the vessel a day later --- unharmed. They do not report what condition kept him out of sight for those two days.
The other risks of MOB are well known from hypothermia developing into unconsciousness. Even with a water temperature between 10ºc and 16ºc, survival time is at the most, six hours, says Martek.
Martek says the solution for vessel and crew to have their own, locally- managed rescue system onboard, with the option to call before calling in the search and rescue services.
It says a beacon to aid MOB alert and recovery can operate on the 121.5MHz frequency, which is the standard for International Emergency Homing, or the 406Mhz frequency, which is a dedicated satellite frequency, giving positioning to an area within three square miles. The 121.5MHz beacons, it says, allow the survivor to be located quickly using a receiver onboard the vessel without initiating a full satellite response, with the distress warning being received within 30 seconds of activation.
However, it adds, the satellite alert transmitted from a 406MHz beacon is not always immediate as the response depends on the receiving satellite and the position of the incident. The response could take hours to be relayed to a co-ordination centre. By the time a 406 MHz alert has been initiated, the MOB situation could have been locally resolved by the vessels crew in a fraction of the time.
406MHz beacons can also generate a problem where there are multiple MOB casualties as the signal that marks the position of the vessel will be obstructed by the casualties' signals and cause confusion when trying to rescue them.
It also says 406MHz beacons do not, as a rule, have the facility to be automatically activated, in part to reduce false alerts to the rescue bodies. But a MOB bashing his en route may be unconscious and unable to trigger his alert.
Their answer, the Crewtrack® operates on the 121.5MHz worldwide emergency homing frequency and has discreet, lightweight personal locator beacons (PLBs) and a choice of emergency receiver units onboard the vessel. In the event of an MOB, a signal is emitted from the Crewtrack® PLB, which the Crewtrack® receiver onboard the vessel will pick up and immediately alert the crew of the situation by means of an audible and visual alarm. If the Crewtrack® direction finder can also be installed on the vessel, a signal strength and position indicator of the MOB will be displayed relative to the ship's heading. To avoid false alarms there is a water-sensitive timing circuit in the beacon which will only activate automatically after immersion for 17 seconds.
