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nupogodi
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:00 am

Quoting BackSeater (Reply 55):
Someone can turn off the DFDR?
But why? An essential piece of safety equipment that uses low power and is fused could create an electrical fire???
Next are we going to talk about spontaneous combustion?

Well, one reason given was that it's procedure to pull it after an incident so it doesn't record over something vital to understanding the incident. But, that is a bit irrelevant with the high-capacity data recorders.

We saw images of the 777 breaker panel earlier in the thread. Way earlier. There was not a breaker specifically labelled for either recorder, but it's possible one of them could be pulled to cut data or power to the recorders. Possible the breakers just weren't on the main panel.

Regardless, you'd want to be able to switch it off. It's not going to save lives to remove that functionality. As I've said before, if you're worried about the people up front sabotaging the mission, you may as well remove the yoke/sidestick and throttles too, because they can be used to crash a plane.
A man must know how to look before he can hope to see.
 
vnangia
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:07 am

Unexpected conference: Ocean Shield has found the signal again. 5 minutes 32 seconds once, 7 minutes xx seconds. Not yet ready to deploy Bluefin 21.

Update 1: they have analyzed the previous signals and have said that the signals are absolutely consistent with FDR signals: 33.331KHz , 1.106 second pulse.

Update 2: search area has been significantly shrunk down. Not clear how much smaller. Ocean Shield detections (all Perth Time):
1. Saturday, 4.45pm
2. Saturday, 9.27pm
3. Tuesday, 4.27pm
4. Tuesday, 10.17pm

Update 3: I'm not a hundred percent what he meant, but he said that they've detected two signals, but not simultaneously.

Update 4, last update: final search area size is 75,000 sqkm.

[Edited 2014-04-08 20:26:30]
 
flyenthu
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:08 am

They found 2 more pings according to JACC. So four in all.
 
Backseater
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:24 am

Quoting nupogodi (Reply 59):
There was not a breaker specifically labelled for either recorder

Before writing my post I looked at the two pictures of the breaker panel and could not find anything that seems to refer to the recorders but I really do not know how they would be labeled.

Quoting nupogodi (Reply 59):
Regardless, you'd want to be able to switch it off

That seems to be the way planes are built today to give the highest authority over everything on-board to the pilot i.e. to "the sole master after God"

What might be worrisome is if the bus interface goes bad on some equipment that is supposed to transmit data over the ARINC 429 and mess up everybody else. But the DFDR only gets data from the bus AFAIK.

If I had a choice, should a "pilot" try to power down the DFDR, I would record that attempt on the DFDR and otherwise ignore the request, unless the DFDR internal temperature sensor shows temperature rising over a certain threshold.
 
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Finn350
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:25 am

Quoting vnangia (Reply 53):
Unexpected conference: Ocean Shield has found the signal again. 5 minutes 32 seconds once, 7 minutes xx seconds. Not yet ready to deploy Bluefin 21.

Great news! It is amazing how with the help of the 'highest probability track' based on the satellite handshake data they have very likely found quite precise area where the aircraft is.
 
nupogodi
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:26 am

Quoting vnangia (Reply 53):
Update 1: they have analyzed the previous signals and have said that the signals are absolutely consistent with FDR signals: 33.331KHz , 1.106 second pulse.

The frequency is quite out of spec, but apparently that's not uncommon. When you say 1.106 second pulse, do you mean 1.106 pulses per second, or something else? Since I'm looking at the DK-series ULBs and they specify *no less* than 0.9 pulses per second so if that's what you meant, that's within spec.
A man must know how to look before he can hope to see.
 
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Finn350
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:31 am

Quoting nupogodi (Reply 57):
When you say 1.106 second pulse, do you mean 1.106 pulses per second,

Apparently the pulse interval is 1.106 seconds, which translates into 1 / 1.106 s = 0.904 Hz = pulses per second, very near the specifiation.
 
rfields5421
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:35 am

Quoting BackSeater (Reply 55):
If I had a choice, should a "pilot" try to power down the DFDR, I would record that attempt on the DFDR and otherwise ignore the request, unless the DFDR internal temperature sensor shows temperature rising over a certain threshold.

Just asking a question, not criticizing.

Have you ever read the TSB report on Swiss 111 ?

If not here is the link:

http://www.tsb.gc.ca/eng/rapports-re...n/1998/a98h0003/01report/index.asp
Not all who wander are lost.
 
tapir
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:36 am

Quoting jetblue1965 (Reply 49):
7. Fly 4+ hours after Banda aceh so the last 2 hours of recording will offer zero useful information to the critical events in the first hour or so

I am not sure if this is exactly true. My understanding is, all data digitally rewritten can be recovered.
 
LTC8K6
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:36 am

Quoting nupogodi (Reply 55):

Frequency due to a weak battery perhaps?
 
nupogodi
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:38 am

Quoting LTC8K6 (Reply 59):
Frequency due to a weak battery perhaps?

Perhaps but it's only been 30 days and it's rated to 37.5 kHz ± 1 kHz for 30 days, but, apparently it's not uncommon, when they powered up the broken AF447 ULBs they were wildly out of spec too. I'm not an electrical engineer I can't speak to the construction of such devices or how an impact might impact (heh) them.
A man must know how to look before he can hope to see.
 
65mustang
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:39 am

Is there any error that a pilot can make that would cause a 777 not to be pressurized? Or asked another way, Once the cabin door is closed and before the plane reaches cruising altitude, does the pilot have to press a button or turn a knob or something to close valves to make the plane pressurized? If the is a button and it is not pressed is there an alarm that tells the pilots that the plane needs to be pressurized?
 
panampaul
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:42 am

Breaking news at 11:30 p.m. EDT.

More pings heard

More Pings Detected in Search for Missing Malaysian Airlines Jet

Quote:
After a day of disappointing news, Australian authorities leading the search for Flight 370 reported that additional signals that could be coming from the ill-fated aircraft’s flight data recorders, known as “black boxes.”

As Wednesday’s hunt began with 14 ships and 15 aircraft in a 30,000-square-mile stretch of ocean located 1,400 miles northwest of Perth, searchers were racing against the clock to locate the flight data and cockpit voice recorders before their emergency beacons die. ...

.
 
LTC8K6
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:42 am

Quoting nupogodi (Reply 60):

IIRC, they only found the CVR pinger from AF447 and it was defective and had never worked at all.

They never found the FDR pinger.
 
Backseater
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:44 am

Yesterday I heard an interview of the President of ULB manufacturer Dukane on NPR. He said he got to listen to the Ocean Shield recording on Sunday, down converted into the normal audio range for humans. He said that it definitely sounded like an aircraft pinger, a little "low" maybe.

He definitely knows his stuff and has a good ear.
 
NAV30
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:45 am

Angus Houston just announced that two signals were 'held' for about 5 minutes and 7 minutes respectively. As a result, he provided some 'good' news - that the area to be searched is now reduced to 75,000 sq. kilometres.........

Quoting jetblue1965 (Reply 49):
His flight path also explains a lot

1. Fly to "roaring 40s" so SAR would be difficult

2. Run out all fuel so minimize chance of explosion or oil slick

3. Gradually land into ocean then let it sink to minimize floatable objects

jetblue1965, the captain was a distinguished professional with a perfect record. Even if he'd decided to kill himself, why on earth would he organise things so that he not only killed 238 other people, but also ensured that their bodies would probably never be found?

Surely all he had to do, if bent on suicide, was go into the bathroom the evening before, and get his razor out?
 
nupogodi
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:48 am

Quoting LTC8K6 (Reply 63):
IIRC, they only found the CVR pinger from AF447 and it was defective and had never worked at all.

Yeah I may have made a mistake when I said "ULBs" but I read that they did power it up to see what it would do.
A man must know how to look before he can hope to see.
 
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Finn350
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:54 am

Quoting NAV30 (Reply 65):
Surely all he had to do, if bent on suicide, was go into the bathroom the evening before, and get his razor out?

If it was a suicide, he must have an additional motive, for example that the act can never be established as a suicide if the aircraft is never recovered (though that seems not to be the case now, but it is very plausible that he didn't knew about the satellite handshakes).

[Edited 2014-04-08 20:54:58]
 
nupogodi
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 3:56 am

Quoting 65mustang (Reply 61):
Is there any error that a pilot can make that would cause a 777 not to be pressurized? Or asked another way, Once the cabin door is closed and before the plane reaches cruising altitude, does the pilot have to press a button or turn a knob or something to close valves to make the plane pressurized? If the is a button and it is not pressed is there an alarm that tells the pilots that the plane needs to be pressurized?

Apparently you can set the pressurization system to manual mode and control bleed air and outflow yourself. That would not be normally done. Yes, there would be a low pressure alarm definitely, and it's been said multiple times that pax masks would drop at 14000ft cabin altitude. It'd be a weird thing to ignore and unintentional depressurization doesn't explain why they flew the way they did.
A man must know how to look before he can hope to see.
 
sipadan
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:00 am

Quoting NAV30 (Reply 65):
jetblue1965, the captain was a distinguished professional with a perfect record. Even if he'd decided to kill himself, why on earth would he organise things so that he not only killed 238 other people, but also ensured that their bodies would probably never be found?

What in the world does being a 'distinguished' professional with a 'perfect' record have anything to do with whether an individual would commit suicide/homicide? You seem to be implying that only 'certain' types of people would be either inclined or capable of executing said acts. Also, I would strongly urge to explore a coinciding political motive...maybe do some research on Captain Shah's political persuasions (ex...he was a friend of Anwar's, the Malaysian opposition leader who was sentenced to 5 years in prison just 7 hours before MH370 departed from KL). Yes, the motives are murky, but politics and mental health are finicky creatures.
 
vnangia
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:03 am

Quoting Tapir (Reply 58):
I am not sure if this is exactly true. My understanding is, all data digitally rewritten can be recovered.

Not if it has been overwritten. There's a long-standing challenge to anyone who can recover any data from a hard drive which has been written over once completely with zeroes, and as far as I know, no one has ever taken it up, let alone win it. It's possible if there was some sort of catastrophe or deliberate action that resulted in a cut in CVR power, then the data is intact. However, if indeed it was left running, it may have been written over at least once, and more likely thrice. Unlikely data is recoverable, sadly.

Edited - it is/was called the Great Zero Challenge, so only zeroed data, not random data.

[Edited 2014-04-08 21:06:22]
 
nupogodi
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:05 am

Does anyone know the mechanism by which towed pinger locators compensate for Doppler? Oddly specific question, but it seems like it might not be able to (since in crude terms you don't really know whether you're comin' or goin') which might explain the frequency shift, but they stated it to quite few significant digits, so I don't even know.

Regardless it's probably them so hopefully we'll have answers sooner rather than later.
A man must know how to look before he can hope to see.
 
LTC8K6
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:06 am

Quoting vnangia (Reply 70):

If, and it's a big if, the hijacker had a suicidal/grudge complex, the CVR may contain a last message.
 
Backseater
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:08 am

Quoting rfields5421 (Reply 57):
Have you ever read the TSB report on Swiss 111 ?

If not here is the link:

Thank you. I only remember reading the summary of the accident report in AWST.
I shall read the report your link pointed to. I was hoping for a PDF file that I could read while flying for 15hrs tomorrow.

If I am not mistaken SR 111 electrical fire was linked to the IFE. IFEs are power greedy. Those I looked at had 1 PC for every 3 seats plus in-seat displays and must have consumed kW. I would definitely leave pilots entirely free to turn off such power hogs. But a low power DFDR?
 
vnangia
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:08 am

Quoting LTC8K6 (Reply 72):

That would simultaneously be awful and relieving - at least we would have an answer even if we didn't like it. Again, depends on whether power was cut and if so at what stage. It'll take a few more months before they get the FDR/CVR up, and hopefully then we'll have a better idea of what happened.
 
nupogodi
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:09 am

Quoting vnangia (Reply 70):
Not if it has been overwritten. There's a long-standing challenge to anyone who can recover any data from a hard drive which has been written over once completely with either zeroes or random numbers, and as far as I know, no one has ever taken it up, let alone win it. It's possible if there was some sort of catastrophe or deliberate action that resulted in a cut in CVR power, then the data is intact. However, if indeed it was left running, it may have been written over at least once, and more likely thrice. Unlikely data is recoverable, sadly.

You are 100% correct, once-overwritten data cannot be recovered from magnetic media. That damn Guttman published his damn paper a long time ago saying it's theoretically possible with magnetic force microscopy, but no one has ever done it, and since then multiple people including Guttman himself and NIST have said that it's not even theoretically possible at today's densities. Yet to this day, poor IT workers are sitting in offices running a 35-pass overwrite algorithm to sanitize drives... Probably browsing reddit or a.net while they do...   But - we digress - the recorders on board this flight were not writing to a magnetic medium but to flash storage, which would also be unrecoverable if overwritten.
A man must know how to look before he can hope to see.
 
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Finn350
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:12 am

Quoting nupogodi (Reply 71):
Does anyone know the mechanism by which towed pinger locators compensate for Doppler?

I doubt there is any compensation. The speed of sound in water is around 1500 m/s. If the vessel travels 1.5 m/s (about 3 kn), the Doppler shift is only about 0.1 %, or 37 Hz for a 37500 Hz signal.
 
65mustang
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:13 am

Quoting nupogodi (Reply 68):
Apparently you can set the pressurization system to manual mode and control bleed air and outflow yourself.

Thanks. So normally, a pilot does nothing to pressurize a plane, the plane does it automatically? And to open the apparatus that bleeds air requires an action by a pilot that would know the results of such action?
 
spacecadet
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:17 am

Quoting 65mustang (Reply 77):
So normally, a pilot does nothing to pressurize a plane, the plane does it automatically? And to open the apparatus that bleeds air requires an action by a pilot that would know the results of such action?

See here (this is a PDF link): http://www.smartcockpit.com/download...th=docs/&file=B777-Air_Systems.pdf

On page 6 you can see the pressurization panel. Yes, every pilot would know how this works.
I'm tired of being a wanna-be league bowler. I wanna be a league bowler!
 
LTC8K6
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:20 am

 
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DeltaMD90
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:22 am

Quoting 65mustang (Reply 77):
Thanks. So normally, a pilot does nothing to pressurize a plane, the plane does it automatically? And to open the apparatus that bleeds air requires an action by a pilot that would know the results of such action?

Without going into details, yes, it does it automatically. Pilots manipulate the bleed air control panel in preflight but not in flight very much (there are circumstances, but not for normal flights.) To open the outflow manually valve, you need to switch the pressurization mode selector to "manual" and then HOLD the outflow valve to open. So I very much doubt it could be done on accident. The only way I can see this being accidentally done is if they put it in manual (due to a checklist directing it) and the pilot accidentally opens it rather than closes it (when the pilot is trying to manually pressurize.) If the pilot is fiddling around with the pressurization, the pilot would probably be monitoring cabin altitude and would probably see the mistake.

Also, I'm talking 737, but I imagine the 777 is very similar. Probably went more in depth than you'd like, sorry  
 
nupogodi
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:23 am

Quoting Finn350 (Reply 76):
I doubt there is any compensation. The speed of sound in water is around 1500 m/s. If the vessel travels 1.5 m/s (about 3 kn), the Doppler shift is only about 0.1 %, or 37 Hz for a 37500 Hz signal.

Wow, 1500m/s is much faster than I would have assumed. Thanks for doing the legwork.

Quoting 65mustang (Reply 77):
Thanks. So normally, a pilot does nothing to pressurize a plane, the plane does it automatically? And to open the apparatus that bleeds air requires an action by a pilot that would know the results of such action?

Ah, that's getting too specific, I don't know, never flown one of these things, only the little things with no pressurization. An Airbus pilot said that it automatically starts pressurizing shortly after takeoff. Boeing apparently does it slightly differently, but the effect is the same, it's automatic if the system isn't in manual mode. Apparently you can go full manual, open the outflow valves, stop the bleed air, and depressurize the plane quite quickly, but pax masks will drop. Unknown to me whether you can block them dropping from the cockpit or if it's a fail-safe. They'll only last for 12-20min though, enough for the emergency decent procedure. Guys (gals) up front would have significantly more, like 2 hours, and cabin crew will have portable bottles...
A man must know how to look before he can hope to see.
 
Backseater
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:39 am

Quoting LTC8K6 (Reply 79):
Map with signal locations.

They do the heavy work and they share. It is a pleasure to rely on Australians for information.   
 
11Bravo
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:40 am

Quoting LTC8K6 (Reply 79):
Map with signal locations.

Still some work to do (and maybe a little luck), but that is looking very encouraging.
WhaleJets Rule!
 
Redsand187
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:41 am

How are they close enough to hear pings, but still have not found a piece of debris?
 
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DeltaMD90
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:43 am

Quoting Redsand187 (Reply 84):
How are they close enough to hear pings, but still have not found a piece of debris?

How many pieces did the plane break into? How much of it floated? How much of that still floated? How big are the pieces?
 
maxpower1954
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:46 am

Quoting LH707330 (Reply 31):
I don't think this is as big a deal as you make it out to be. I challenge you to walk down the street and ask passers-by what they think of Adam Air 574, Silk Air 185, LAM 470, Egyptair 990, and I bet most people won't have a clue what you're talking about

Adam Air 574 wasn't a suicide. If previously corrected, sorry - I missed it.
 
LTC8K6
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:54 am

Quoting BackSeater (Reply 82):

They are all over that Inmarsat arc, too...
 
tapir
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 4:55 am

Quoting vnangia (Reply 70):
Not if it has been overwritten. There's a long-standing challenge to anyone who can recover any data from a hard drive which has been written over once completely with zeroes,

I really do not know how a black box recorder works but digital medium that randomly rewritten or deleted capable of being recovered. I have recovered photos long deleted and the memory card has been deleted twice for being full. I think the same principle applies where they (FBI?) recovered the deleted data from the pilot's sim.

[Edited 2014-04-08 21:56:41]
 
LTC8K6
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 5:02 am

Quoting Tapir (Reply 88):

Deleted is not the same as overwritten.

Deleted generally means the data is still there, the areas are just marked as empty.
 
LTC8K6
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 5:04 am

Quoting BackSeater (Reply 82):

Apparently cooperation too, with the locator borrowed from the US Navy.

http://ui.sina.com/2014/0331/U45P5029DT20140331083617.jpg
 
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ssteve
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 5:10 am

Quoting Tapir (Reply 88):
I really do not know how a black box recorder works but digital medium that randomly rewritten or deleted capable of being recovered. I have recovered photos long deleted and the memory card has been deleted twice for being full. I think the same principle applies where they (FBI?) recovered the deleted data from the pilot's sim.

"Delete" in most filesystems is lazy-- the data bits aren't overwritten. They're still there. The filesystem is just instructed to forget about them and allow them to be overwritten later.

Like you, I've recovered deleted photos, but that's only possible because they haven't been overwritten. When selling a laptop, it's advisable to run a utility that writes random data to the entire hard drive to ensure that your data is not recoverable. Similarly, if an FDR is filling its memory with data, the previous data set is not recoverable... it's been overwritten, unless the new data is somehow more sparse than the old.
 
nupogodi
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 5:11 am

Quoting Tapir (Reply 88):
I have recovered photos long deleted and the memory card has been deleted twice for being full. I think the same principle applies where they (FBI?) recovered the deleted data from the pilot's sim.

No no no this is very different. In your scenario the blocks/sectors/whatever were marked as being free in the file system ('deleted' by any other name) but were not overwritten. It gets a little bit murky with flash media because of write-levelling algorithms in the actual controller, but - we're talking about different things here.
A man must know how to look before he can hope to see.
 
65mustang
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 5:13 am

If there are alarms and cabin mask drop at 14000ft cabin altitude it is unlikely there was a pilot mistake re pressurization that could mot have been corrected.

About the cause of the 8:19 partial ping

The prevailing idea behind the partial ping is that there was a loss of power to satcom and that it tried to reconnect via satellite to a ground terminal when power was restored to it. From the B777 electrical manual on smartcockpit i found the following:

"The power sources normally operate isolated from one another. During power source transfers on the ground (such as switching from the APU generator to an engine generator) operating sources are momentarily paralleled to prevent power interruption."

"The backup electrical system is designed to automatically provide power to selected airplane systems. The backup electrical system automatically powers one or both transfer busses when:
• only one main AC generator (includes APU) is available
• power to one or both of the main AC busses is lost
• approach (APP) mode is selected for autoland
• the system is automatically tested after engine starts.
The system transfers power without interruption."

I could not find where the manual specifically said that power is transferred in parallel in the air, but if it does, how would satcom lose power?
 
LTC8K6
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 5:18 am

Quoting SSTeve (Reply 91):

The CVR would be overwritten if it was not disabled as it only records 2 hours of data.

The FDR should be fine if it was not disabled as it records 25 hours of data.
 
LTC8K6
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Joined: Fri Jun 05, 2009 8:36 pm

RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 5:20 am

Quoting 65mustang (Reply 93):

I could not find where the manual specifically said that power is transferred in parallel in the air, but if it does, how would satcom lose power?

There could be a delay with the APU autostart failing due to lack of fuel?

The RAT must take a moment or so to deploy as well.
 
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Finn350
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 5:21 am

Quoting LTC8K6 (Reply 79):
Map with signal locations.

When looking at the map, the furthest detections are almost 20 km apart. Assuming both the recorders are near each other, that would point to a location that is somewhere in the middle of all the detections (as hearing signal 20 km away would be a stretch).

Quoting 65mustang (Reply 93):
I could not find where the manual specifically said that power is transferred in parallel in the air, but if it does, how would satcom lose power?

Power sources can be paralleled only when both the power sources are operative. When one power source fails, and that triggers the transfer, the transfer obviously cannot be parallel.
 
nupogodi
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 5:25 am

Quoting LTC8K6 (Reply 95):
The RAT must take a moment or so to deploy as well.

That is what the guy who tried a 772 fuel-out hands-off scenario in the certified sim said. CDU and copilot PFD was dead for a while and they entered a descent past V_mo, before the RAT brought those back online.

Clearly we can't try this with a real plane but I trust the sim.

[Edited 2014-04-08 22:27:31]
A man must know how to look before he can hope to see.
 
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Starlionblue
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 5:45 am

Quoting BackSeater (Reply 48):
That sounds ominous in the MH370 case. Someone can turn off the DFDR?
But why? An essential piece of safety equipment that uses low power and is fused could create an electrical fire???

Same reason as most anything else can be powered off, no matter how small. If it is electrical, it can create problems.

Important point in context: DFDRs and CVRs are in no way essential pieces of safety equipment. They do absolutely zero for the safety of the flight. Their use is after an incident or accident, to make future flights safer.

Only really flight critical stuff is on the essential bus (or whatever Boeing calls it). Things like flight controls and the coffee maker.

Quoting nupogodi (Reply 50):
We saw images of the 777 breaker panel earlier in the thread. Way earlier. There was not a breaker specifically labelled for either recorder, but it's possible one of them could be pulled to cut data or power to the recorders. Possible the breakers just weren't on the main panel.
Quoting BackSeater (Reply 53):

Quoting nupogodi (Reply 59):
There was not a breaker specifically labelled for either recorder

Before writing my post I looked at the two pictures of the breaker panel and could not find anything that seems to refer to the recorders but I really do not know how they would be labeled.

IIRC there are like four or more breaker panels in the cockpit alone, plus more in the avionics bay. I think the pics we saw were only of the overhead ones.

Quoting DeltaMD90 (Reply 85):

Quoting Redsand187 (Reply 84):
How are they close enough to hear pings, but still have not found a piece of debris?

How many pieces did the plane break into? How much of it floated? How much of that still floated? How big are the pieces?

I'll add to that list. How long has it been since the plane vanished? How many storms have been in the area? (Two.) How bad is the weather in the area? How high are the waves?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
nupogodi
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RE: MH370 Malaysia Airlines B772 Missing Enroute KUL-PEK Part 52

Wed Apr 09, 2014 5:46 am

Also, as long as we're going to continue to inject a bit of humour when we can - I saw a funny post on PPRuNe that suggested we train dolphins to locate ULBs. It could work, and they're certainly cheaper than ships! But then someone pointed out that the service depth of dolphins is really not that great. Oh well.  
A man must know how to look before he can hope to see.

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