Originally Posted by
Kingbird87
If I am not mistaken,the ELT and the FDR both communicate through VHF and UHF frequency, and a VLF pinger, and we picked up the pinger in the vicinity of on Northern Hokkaido enroute to the AO. You are correct about the sound waves of SONAR. That is why we had a Radio Operator on the HC-130 and knuckle dragging pilots to fly the airplane. He got the DF steer off the tracker, and I thought it was only possible with VHF, UHF, S-Band and HF. The pinger indicated location through receiver intensity. Somehow we were accurate enough for 2 SU-15's and three Mig 23's to launch on us. This was also the only mission I ever flew where the PJ's did not want to jump.
ELTs are radio only, no sonar. Modern ones use EHF, older ones VHF. As was mentioned only ELF radio can penetrate any depth of water and that requires an antenna array larger than almost any other structure on earth. The US navy used to use that to communicate with subs. Maybe you had that?
FDR and/or CVR have a sonar pinger activated by exposure to water. That sound would be detectable only by military sonar receivers or specialized civilian gear. It would not be detectable by a radio receiver, I don't think FDR/CVR even have radio beacons...assumption being if the wreckage is on land the ELT would provide the beacon.
Not sure how you located KAL unless the ELT was floating or very, very shallow. Aircraft can easily use sonobouys to detect/locate underwater sound sources, but it requires special onboard receiving gear normally found on navy aircraft.