Malaysian Airlines MH370 contact lost

[hamster3null]

Originally Posted by DocRohan

@slats.
I am not sure that there would be much value in determining carboxyhaemoglobin or lactate levels in blood from bodies immersed in hypertonic salt water...Likely the hypertonicity would significantly alter biochemistry.
Examination of lungs and detecting diatoms could give an indication of whether people were alive or deceased prior to immersion, although this is still not 100% conclusive at autopsy.
(apologies for graphic content)

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.

[fantom]

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?

Water.

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

[grimmrad]

@ 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?

[Niner Lima Charlie]

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.

[nupogodi]

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

[hamster3null]

Originally Posted by grimmrad

@ 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.

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.

If there were indeed 2 pings: feasible that one signal would be carried 600 km and heard by the other device?

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.

[flash8]

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.

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.

[Speed of Sound]

ULBs

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?

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?

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.

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.

[JamesCam]

Originally Posted by Niner Lima Charlie

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.

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?

[mm43]

Surely the device is crystal controlled?

Ever dropped a crystal and wondered why it then didn't perform?

[silvertate]

transponder always on

Kooljack:

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

....except, it is still accessable to the pilots.....

Except that most aircraft i have flown, the E&E is most certainly not accessible to the crew. Unless you have hidden a chain-saw in your flight bag !!

A transponder-CB in the E&E bay, and no off-switch on the unit, would be tamper-proof and would also isolate any equipment failures. The on switch could be activated by N2 rotation, as that is when ATC normally want it on - and N2 rotation will remain even with a double engine failure. Is that a difficult concept to understand?

[underfire]

3 separate search areas


By itself
OCEAN SHIELD
Position Recorded on:
2014-04-07 18:00:28 (UTC)
Lat/Lon: -20.88497 / 104.1175

with 2 other vessels in S search area
HMS ECHO (British)
Last Position Received: 2 h, 29 min ago
Area: Indian Ocean
Latitude / Longitude: -26.05799 / 101.427

Warship Perth, Warship Success, HMS (Malaysia) Warship, and NAN HAI JIU 115
Info Received: 2 h, 33 min ago
Area: Indian Ocean
Latitude / Longitude: -20.91343 / 97.83881

[JamesCam]

Originally Posted by mm43

Ever dropped a crystal and wondered why it then didn't perform?

Modern crystals are very small and lightweight; mil grade oscillator units will survive 1000g shocks. further to that, the electronics is contained in a shock absorbing sub container.

Anyway, even a decent LC oscillator will have better frequency stability over varying supply voltages than the performance described in the OP's post!

[GroundedSpanner]

Re ULB's

Quote:
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.

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.
Speed of Sound is online now

The unit retrieved from AF447 emitted 34KHz in testing with a fresh battery.
http://www.bea.aero/fr/enquetes/vol....ion.report.pdf

[Walnut]

Sandiego89 suggested that the 777 has an excellent safety record it does. However it does have history of MEC electrical fires which could be the initial cause of this incident. I suggest that he reads 9392 & 9395 to get the background The AAIB report of the US incident in Feb 2007 made several recommendations which were not fully taken up by Boeing & the FAA. Smoke & fire on an a/c can be killers, as such it may have been the trigger for what happened to MH370

[henra]

Originally Posted by sooty655

Perhaps the Chinese heard through the search grapevine that Ocean Shield was picking up (and trying to verify) recorder pulses, but had not yet gone public. Maybe they decided to claim a first for their own public relations reasons.

But why would they then report a Position that is >300NM away from Ocean Shield's?

The almost synchronous finding by the Chinese is a really intriguing thing. Maybe they had a different yet secret way to determine a likely position which delivered results a bit off.
Anyway I still have a very hard time believing that their reported way of obtaining the Signal (handheld device from a RIB) was the real deal.
Too much noise around the surface, too much layers in the water below, too small sensor. And then only short hearing and no recording, read no proof. That doesn't add up.
The Ocean Shield finding on the other Hand sounds much more convincing.
Longer recordings, plausible Equipment for the Job.

[sooty655]

Originally Posted by henra

Originally Posted by sooty655

Perhaps the Chinese heard through the search grapevine that Ocean Shield was picking up (and trying to verify) recorder pulses, but had not yet gone public. Maybe they decided to claim a first for their own public relations reasons.

But why would they then report a Position that is >300NM away from Ocean Shield's?

The report was released to Chinese media via their media contingent on the Nan Hai Jiu, so they could only use the position they were in. They could hardly claim a >600NM round trip for their RIB.

[BrookeEngineer]

Hydrophones etc

The input frequency is translated to something you can hear.

The PSR-1 VIetnam era seismic intrusion detector has input frequency that's well below human hearing and shifts that up. When you hear the shifted sound you know what you are hearing, i.e. a man or woman or child walking, a cat, a dog etc.
PSR-1 Seismic Intrusion Detector


If you want to listen to the pings from bats which are ultrasonic you use a converter that translates that down to human hearing.
Listening to Bats
This unit has two mikes and so you get stereo which helps a lot in knowing where to look.

[Propduffer]

My understanding is that underwater sounds can reflect back off the bottom and / or thermal layers in unpredictable ways. There are tales of submarines being tracked from more than a thousand miles away under the right acoustic conditions. I have no problem imagining that a pinger's signal could turn up three hundred miles away. Also, the only way I could imagine parts of the plane coming down 300 miles apart is if it was high up on re-entry al la space shuttle. I also can't imagine any fish making a love call on 37khz or so with a pulse repetition frequency similar to an underwater beacon.

And there is no reason to doubt the Chinese in this matter, unless you (or someone) dislike Chinese and are allowing that to cloud their judgement

This is the same signal.

[Mesoman]

Why to doubt the Chinese

And there is no reason to doubt the Chinese in this matter, unless you (or someone) dislike Chinese and are allowing that to cloud their judgement

• The Chinese did not record the signal, they just listened to it. This reduces the credibility a lot. It's very easy to hear what you want to hear - to imagine you hear a weak signal that is not there.
• The Chinese picked up the signal at the surface. It is unlikely that it could be heard that far from the bottom.
• The signal could not have traveled the distance between the Chinese and the Aussie detection. Signal attenuation due to both distance and energy losses (from non-adiabatic compression of ocean water) of ultrasonic signals prohibit it. It *could not have done it.* This isn't a matter of it maybe didn't do it - this distance is orders of magnitude too far. Even ducting wouldn't do it - and if it were being ducted, only one of the two parties would have heard it, since they were listening at greatly different depths.
• The US detector was recorded. It showed a solid signature. The people doing the US detection are experts at this thing.

None of this is to imply that the Chinese did anything wrong other than being over-eager - a common problem in SAR/