Egyptair 804 - Black Boxes

[ab5r]

Perhaps someone here can enlighten me. A few days ago I watched a special named "SONIC SEA" that proposed the idea that sounds carried in the oceans traveled hundreds of miles and were effecting dolphins and whales detrimentally. They said an experimental sounding device was placed in the middle of the Indian Ocean and heard near san Francisco.

If this is accurate, why do the "black boxes" pinging away for days not heard. What is the difference? Is it the frequency of the ping; volume or what? Is it that they CAN be heard, but not triangulated?

Yep, I'm confused.

 

[majoco]

Whales can communicate over vast distances, south to north pacific for instance, but they use very low frequencies. The locator pingers emit a very short 10mSec beep every second on 37.5kHz. Our whale example is difficult to direction find as there are multiple echoes from all directions but the pinger being low powered and higher frequency has a limited range so there are few echoes to avoid confusing the locator receiver, just like the sonar equipment on a submarine which has two modes, one to listen to it's own ping like a radar, or to listen for someone elses ping and DF on it.

Wiki has a good page on it, except that say that you can change the batteries - never done that - always sent the unit back to Dukane. They say that the pinger can be detected up to 5km on a good day - trouble is, ISTR that the Med is about 5km deep there!

 

[ab5r]

EXCELLENT reply Martin. Thanks. I did not know much about the black boxes. Could you please give the Wiki's correct URL, please.
Jerry

 

[RFI-EMI-GUY]

Look here!

https://en.wikipedia.org/wiki/Underwater_locator_beacon

 

[poltergeisty]

They need to make these things float! I believe military aircraft do this.

 

[RFI-EMI-GUY]

Black boxes and pingers are unlikely to float from wreckage even with some buoyancy device. Most of them have extreme damage to the casing from impact. You would need an armored housing to encase the flotation device and then some explosive or energetic mechanism to release it.

ELT's have a surprisingly low success rate after crashes. like 35% activation, even though aircraft have two to four of these.

What they really need to do is install asset tracking GPS devices way up on the tail of the aircraft, with battery UPS, tamper proof and unreachable without a man lift. They should report the location of the aircraft every few minutes via satellite. It makes no sense to have a $100 million asset that can be flown anywhere on the planet and have no expectation that it be located if it goes down.

 

[RFI-EMI-GUY]

Whales can communicate over vast distances, south to north pacific for instance, but they use very low frequencies. The locator pingers emit a very short 10mSec beep every second on 37.5kHz. Our whale example is difficult to direction find as there are multiple echoes from all directions but the pinger being low powered and higher frequency has a limited range so there are few echoes to avoid confusing the locator receiver, just like the sonar equipment on a submarine which has two modes, one to listen to it's own ping like a radar, or to listen for someone elses ping and DF on it.

Wiki has a good page on it, except that say that you can change the batteries - never done that - always sent the unit back to Dukane. They say that the pinger can be detected up to 5km on a good day - trouble is, ISTR that the Med is about 5km deep there!

Also those thermoclines tend to trap the sound and duct them far away from the area of interest. Perhaps the MH370 false detection's were from such a cause.

 

[poltergeisty]

Black boxes and pingers are unlikely to float from wreckage even with some buoyancy device. Most of them have extreme damage to the casing from impact. You would need an armored housing to encase the flotation device and then some explosive or energetic mechanism to release it.

ELT's have a surprisingly low success rate after crashes. like 35% activation, even though aircraft have two to four of these.

What they really need to do is install asset tracking GPS devices way up on the tail of the aircraft, with battery UPS, tamper proof and unreachable without a man lift. They should report the location of the aircraft every few minutes via satellite. It makes no sense to have a $100 million asset that can be flown anywhere on the planet and have no expectation that it be located if it goes down.

The "deployable" CVDR technology has been used by the US Navy since 1993

https://en.wikipedia.org/wiki/Flight_recorder#Proposed_requirements

 

[majoco]

ELT's have a surprisingly low success rate after crashes. like 35% activation, even though aircraft have two to four of these.

Ship ELT's are usually attached to the structure externally by a dissolvable latch and floats to the surface. They use a salt-water battery and if the water is shallow it remains attached by a long line. If the line becomes taught then a release mechanism lets it go to the surface, a sea anchor prevents it drifting away too quickly.