LeadTurn_SD
Contributor
Out of curiosity. How is LOS for aircraft when the source is at sea level? I'd imagine it's range to be larger and be power limited instead of being horizon limited, would this be correct?
Also, yeah, I forgot about ELPBs
Depends on altitude of the search aircraft.... but yes, the detection range would increase a lot.
Somewhere buried among my old navigation stuff is a table for computing distance to the horizon based on "height of eye". The visible horizon is much closer than you think it is due to the curvature of the earth, and bobbing in that water the horizon is not far at all. Searching from the air, the limitation would more likely be the power of the transmitter, and position of the aircraft relative to the person in the water (swells could still block line of sight between aircraft and the diver if the aircraft were too distant).
EPIRB or PLB's transmit to overhead satellites, so line of sight is not an issue. Most (All of them these days? Sorry, I'm not at all current...) also transmit your GPS position, which drastically narrows down the search area.
A hand held VHF could be useful to talk to an overhead aircraft, or to your dive boat if you were still basically in visual range or just slightly beyond.... but I'd carry the PLB, not a VHF.
Best wishes.