A 40 ft yacht returning to Britain from the West Indies with four on board went missing 1000 miles off Cape Cod Friday morning. Their last radio report was that they were taking on water, but were stable, and diverting to the Azores. Visibility was 1 mile or less, 30-50 knot winds, 13-15 ft seas. After 2 days of searching by 3 C-130s and 3 merchant vessels, the search was called off.

Two 406 MHz personal locator beacons were activated. US Coast Guard, US Air Force, and Canadian Air National Guard C-130s flew to the transmitted GPS coordinates, but no luck. Small pieces of debris was spotted, and and an inverted hull was spotted, but not investigated.

Since PLBs also transmit a 121.5 Mhz homing signal, and the USCG says they can also home on the 406 Mhz signal, it seems like the visual visibility would not have been the limiting factor. I wonder at what range the C-130 can detect those homing signals? I found a spec sheet for a PLB homing receiver for airborne SAR here, but detection range isn't evident to me.

USCG Bulletin announcing end of search
USCG audio interview on BBC
USCG Initial Report
BBC News report at search end
Daily Mail report at search end The Guardian report at search end