It seems a pity they do not operate a TPL pair.

"Flying" two locators, perhaps 1000m separation, would be manageable when cable lengths are over 10,000m and they only each require a co-ax pair.
That would provide wider search sweep and lateral location.

lucille:-
Interestingly, I could have sworn I saw a freq of 87.1 kHz on their display....

transponder always on
 

You put a CB down in the E&E bay, where nobody can touch it. Just like they do in Airbuses.

BillS, #9512:

In wonder if they have the capability to use sar techniques to get a better idea of position. I know the pinger is one way, but it should be possible to correlate reception over time, especially if sweeps are done orthoganally...

Looking at the cascade plot posted by Cloudbase4812 there appears to be only one clear signal repeating at set intervals.

This would seem to signify that either the CVR and FDR have been separated or that one has stopped pinging.

Is there any way to differentiate which unit is radiating?

silvertate:-
....except, it is still accessable to the pilots.....:ugh:

One reason to recover the hull is that the pax may have recorded their experience of the flight, in forms that can still be read.

Isn't that what arc-fault breakers are supposed to fix?

Slight thread divergence here but could someone tell me exactly what starts the black box transmitter off? Would a heavy landing do it for example or conversely would a very soft landing on water not do it?

AIS Marine Traffic

With Marine Traffic, you can see the ships, and by clicking on them, show their tracks...

(I manually added the ship names as you can only view one at a time...)

http://i57.tinypic.com/t817a8.jpg

Sonar Pulse Range in Water
 

Dai Farr - A fine summary

Long ago in another job I designed the electronics for hydrographic survey work. Things have changed a lot since then.

Those who have followed this thread have heard that the range of the ULB is likely to be 600 or 800 or 1500 or 2000 metres. We have seen the photo of the ULB locator on the small Chinese boat - with headphone monitoring.

Typically those receivers are tunable and have a bandwidth of about 1 to 3 KHz. The range of detection that has been bandied about is probably about right: .6 to 2 km for that sort of detector.

But with modern technology and a pulsed carrier ultrasonic transmission with reasonable stability one can use a very narrow band detection scheme.

Reducing the received bandwidth to 10 Hz could increase the detection range by a factor of 10 or more (without benefit of any ducting contributions). If the signal from the ULB is sufficiently stable in frequency, going to a coherent detection scheme and slightly narrower bandwidth and gating the receiver at the sonar pulse rate could possibly achieve a detection range of 10-30 km. The major limitation on this sort of scheme - it would only work with a non-moving vessel due to doppler shift becoming a major contribution to the frequency. But that can easily be addressed with modern DSP techniques. Having 500 or 1000 virtual receivers (it's only software) focused on detecting carriers every 2 Hz across the spectrum would be easy. And once the carrier is found, the doppler shift would become a viable cue for deciding which direction to move in search of the ULB.

Pure speculation: this technique is being used right now. I am wondering if the Benthos ULB locator was shown on the small Chinese rubber boat for show only... It would be a nice way to get the report out without disclosing some more serious sonar analysis capabilities.

By complete coincidence my work this last week has been focused on analysis of sonar reflective returns at 40.0 KHz

Hypertonic or not, salt water is still basically water and electrolytes, I don't think that it would mess with lactate, except through simple diffusion.

I'm skeptical about these tests too but for a different reason.

CO poisoning is one of the less likely things to kill you in a fire, it usually happens during prolonged exposure to gases from a poorly ventilated furnace or an internal combustion engine. CO only forms in the presence of insufficient supply of oxygen. CO poisonings are common in general aviation, and almost invariably occur when piston engine malfunction results in the exhaust gas being pumped into the cabin. The only large jet incident I could find was caused by a malfunctioning air conditioner. A fire that gets to the point where hazardous levels of CO are produced would pose a high risk to structural integrity of the aircraft, and there would be ample direct evidence of that.

CO could be one of the things to look for, but it would indicate a mechanical problem, like the aforementioned air conditioner, rather than a fire.

I don't think that lactate forms in significant quantities during hypoxia if the person is stationary.

In both cases, there should be more obvious physical signs, e.g. soot in the lungs to indicate a fire.

Water.

10 dots to comply..........

@ DocRohan: Carboxy-Hemoglobin - CO binds 250-stronger to Hgb than oxygen, so if samples were to be retrieved containing erythrocytes it should be possible to evaluate that to indicate a fire. Osmotic strengths will have the cells burst but if the Hgb is not washed out it should be possible for forensics to evaluate that, it would not interfere with the binding affinity of gasses to Hgb. Ionic strength (9% NaCl in sea vs 0.9% physiologic conditions) could interfere with the binding of CO2 to Hgb's amine-groups but that accounts for only 10% of the binding.

If there were indeed 2 pings: feasible that one signal would be carried 600 km and heard by the other device? Or maybe both boxes (voice and data) at different locations? Implications of that?

It was reported in Perth that the Australian Navy "Ocean Shield" detected the first signal and tracked it for two hours and 20 minutes. Then turned around and tracked a second signal for 13 minutes. These pings were on 33.3 KHz rather than 37.5 KHz, which the pinger manufacturer says would account for drift due to low battery after 30 days active.

If Ocean Shield heard the recorders, what the hell did the Chinese hear?

Carboxyhemoglobin occurs naturally in the blood and its levels can be further elevated in smokers. So you can detect an exposure that is high enough to cause acute poisoning, but you can't confidently detect, say, 10% of that exposure.

Roughly as feasible as having a rock band perform an open-air concert in New York City and hearing their songs in a field in Ohio. (Sound attenuation in air at 1 kHz is similar to sound attenuation in seawater at 37 kHz.)

In other words, we have too many pingers.

That is a fair point that hadn't occurred to me. Given the proliferation of devices nowadays, and the relative integrity of solid state, it may just assist enormously.


Back in 1979 during the ANZ DC-10 CFIT the team recovered a film camera that had an exposure taking by a passenger (after all this was a sightseeing trip) at the exact hundredths of a second before impact, showing snow scattered by the impact of the hull. The passenger passed from life to death in that split period.

Point here is loosely that the intelligence picked up from the tourists film cameras was invaluable assisting in tracking the final moments.

ULBs
 

I doubt it.

Unless the two signals are modulated in some way I would say that they are identical. Besides, does it matter which unit is transmitting as long as one of them is found?

I would be very surprised if that were true. As battery life reduces it is the amplitude of the signal which will reduce, not the frequency.

I find it extraordinary that the ping frequency apparently changes so dramatically with power supply voltage! Surely the device is crystal controlled? what use is a device like this if the frequency one is looking at is effectively unknown. To detect the signal at a distance one needs to use very narrow bandwidth filters of the order of only a few Hertz: here we are talking about a shift of 4.2KHz, well over 10%...

I don't believe this equipment performs this badly, given it's designed role. was the Ocean Shield following something else? can someone quote the source of the "manufacturer's" comments?