If you are using a GPS unit then it uses geostationary so no need for a sat to pass. But the possition data will need a GPS fix which in a chop from a satelitte niave unit takes a lot longer than you'd expect - hence the 15mins people talk about.
Some of that will depend on location. Other vessels in the area, complexity of getting aircraft there.
So you suddenly realise your crew is missing. You hit the red button on your DSC. It re-tunes to channel 16. You transmit "Mayday, Mayday Mayday this is Yacht ABC, ABC, ABC. MMSI 123456789. I have a Man over board. My current position is ABC. I have been sailing on a course of XYZ. MOB has occurred in the last X minutes. I require urgent assistance. Over."
If the PLB has no GPS your search area is bloody large! OK not quite like looking for an aeroplane in the Indian Ocean but something like 5sq km, and with a time delay of 30-90 minutes. You would need a 121MHz homing device to get a decent fix so you need the bird or the RNLI to help you.
Not my understanding but if there are multiple numbers they try them all and they would try and contact via VHF use any other intelligence they have such as a reported passage plan, AIS etc. If they know you are out there and are uncontactable they are likely to ask other vessels for any information if they know there are commercial vessels in the vicinity. At the same time they may be tasking a helo or occasionally a LB to investigate.
The check for NOK confirmation takes about 40 minutes; if no response that all is well then SAR is launched. The reason the NOK calls are made is important - it's reduced false alarms resulting in SAR to below 5%, and that gives the CG huge confidence that it's worth searching! Interestingly a non GPS PLB alerts the CG at the same time as a GPS one, the only difference is that it doesn't give immediate position detail. The time taken usually to get a position fix good enough for an SAR operation is about 45 minutes, with two hours being the maximum providing no transmission issues. In practice that means that the PLB with or without GPS alerts the CG at the same time and SAR is activated at almost exactly the same time. The actual finding is done by the homing signal identical on both units; the addition of GPS therefore adds very little to a PLB's real world functionality, costs pennies to add on but enables a £70 price difference - I still bought one with GPS though, you just do don't you
The actual finding is done by the homing signal identical on both units; the addition of GPS therefore adds very little to a PLB's real world functionality, costs pennies to add on but enables a £70 price difference - I still bought one with GPS though, you just do don't you
