From a thread by Tradewindsailor on ybw.com today, EPIRB stuff at bottom relevant:
According to this facebook thread:
the NZ searches were concentrated to the NE of an erroneous Iridium
position. The last position given by the crew looks to be about 150 miles to the West of the Iridium
position and consistent with the actual position reports. This would put them on the NW sector of the low pressure system (low pressures are clockwise South of the Equator) and hence they would be being pushed to the N and NW.
A lot of speculation has focused on that there have been no comms since 4th June. No comms is simply that: no communication. It doesn't mean that there are no survivors, and it certainly doesn't mean that Nina had sunk.
Nina had the Iridium phone
(non-gps), a SPOT device that reported simple messages including the position, an Epirb, and a VHF
is of use only as a line of sight comms ..... up to 17 miles yacht to yacht, more to a ship, and much more to an aircraft (75 miles?).
The Iridium phone
had been good up to the 4th. The last message was sent to the Iridium system on the 4th, but not found until about the 25th June from my recollection. Could it be that the Iridium phone was faulty after the 4th? Could the last text message have been stored in the phone only to be sent when it was next turned on? I don't know. One thing I am absolutely certain about is that the Iridium phone was not a reliable means of communication, and an even worse position indicating device. Why was it used by the authorities to base a search when better information was at hand?
The EPIRB. I understand that the EPIRB was a non-GPS unit. No EPIRB emergency
signal was received from the Nina. The EPIRB would only be used in circumstances where a MAYDAY would be initiated. If the NINA was floating and navigable, I doubt if the EPIRB would be activated. BUT at sometime between the 4th June and now circumstances must have deteriorated enough for the EPIRB to have been activated. So why no EPIRB signal?:
1 It is possible that the EPIRB could not be reached if they had to abandon NINA quickly
2 The EPIRB may not have generated a signal that was accepted as a bonefide distress
message and hence ignored by the system.
3 The EPIRB could have passed the self-test but still failed to operate correctly. The self-test is purely internal to the EPIRB. No transmission
is made at all, so it is not a test that checks the entire system.
4 It would take up to 'a few hours' according to the USCG for this type of EPIRB to generate a position fix into the system. I understand that if the position fix is not completed, the emergency
message is not sent .... I am awaiting confirmation on this.
5 The antenna
would not be checked by the self-test as there is no transmission
. There have been failures of antennas in the past ..... cracking of the rubber antenna
casing leading to corrosion
of the internals. No antenna .. no message.
6 The condition of the battery
is not properly checked during the self-test. The batteries generally produce the required voltage even though they may be short on capacity. They are known to self-discharge at much higher rates in warm weather
.... and the NINA spent a lot of time in the tropics at around 30 deg C, more if the unit housing was heated by the sun or engine
. There are incidences reported on the internet where EPIRBS have failed to send the message due to bad batteries, or have only operated for a few hours .... see 4 above.
7 I have been unable to obtain any data from the authorities where vessels that are fitted with EPIRBS have been lost
without an EPIRB message being received, or any other case where EPIRBS have been activated and the message has not been received.
8 What are the effects of weather
condition on EPIRB transmissions, especially when operated in bad conditions from a liferaft
or in the water
SO : NO COMMS DOES NOT MEAN "NO SURVIVORS"
I hope the authorities can comment any of the above, particularly if I have made a mistake.
Most of all, I hope the crew are found alive and well. Remember there are cases where survivors have been found after 117 days adrift in a liferaft
...... and that the Spirit of Baltimore
went down with her EPIRB, but some of the crew were rescued several days later by a passing ship.