French airliner missing over Atlantic

[Thanas]

German radio news report wreckage has been found.

[Broomstick]

Several other media outlets are also reporting that. Still hoping for some survivors although I'm well aware of how unlikely that is.

[Surlethe]

WSJ news alert:

Brazil's air force said Tuesday it had found remains of an airplane in the sea near where an Air France flight bound for Paris with 228 people on board disappeared after encountering turbulence.

Air force officials said a search aircraft had spotted debris about 650 kilometers (400 miles) off of Fernando de Noronha, an Atlantic island near where Flight 447 last made radio contact on Monday night.

For more information:
http://online.wsj.com/article/SB1243943 ... malertNEWS

[FSTargetDrone]

One bit of information to emphasize what the recovery effort would involve:

"The Airbus fell into an area of the sea where the Atlantic is more than 9,000 metres deep,“ Brazilian aircraft commander and chief pilot Douglas Ferreira Machado said.

I think it will be a challenge to recover, let alone find, the flight recorders. The aircraft will have broken up after hitting the water (assuming it wasn't already a rain of debris coming down to begin with) and if the area on the plane (tail or nose, elsewhere?) where the flight recorders are located wasn't destroyed, the recorders may still have fallen well out of reach on their way down. In other words, if the flight recorders didn't somehow manage to stay attached to a hypothetically large chunk of the aircraft and if that section could be located and raised to the surface, they may never find those recorders at all. The debris field may be scattered all over the ocean floor for some distance. Potentially over many kilometers, right?

[Stuart]

The latest word is that there are two seperate areas of wreckage, suggesting that something fell off and then the bird went in. Frankly I'm begining to agree that we'll probably never find out exactly what happened.

[FSTargetDrone]

Here is a Telegraph story (I don't believe it was discussed here--I can't find anything in the archives) from today about a Qantas Airbus 330 that had a computer error last October causing the aircraft to unexpectedly descend which then resulted in injuries onboard:

Air France plane: Airbus has had computer problems in the past

The disappearance of the Air France Airbus A330 came eight months after a similar aircraft plummeted more than a thousand feet without warning over Western Australia.

By David Millward, Transport Editor
Published: 7:00AM BST 02 Jun 2009

More than 100 passengers were injured, some seriously, when the Qantas operated aircraft, suffered electrical problems last October.

According to the Australian Transport Safety Bureau, investigators pinpointed a fault in one of the flight computer systems as a potential cause of the near disaster.

There are more than 600 A330s in the skies and they are regarded as a long-haul workhorse by the industry and used by 72 operators.

They are not used by either British Airways or Virgin, although Bmi does have three.

James Healy-Pratt, head of aviation at Stewarts Law, said the Australian incident indicated there could be problems with the A330's avionics systems – the computers used to control the aircraft.

"We are already acting on behalf of 30 families who were injured in the Qantas flight and we will no extend our investigation to cover this incident as well," said Mr Healy-Pratt.

"In the case of the Qantas flight, there was a serious malfunction of one of the computers," he said.

The Airbus relies on a computer to operate all its hydraulic systems – such as the rudder and a flap known as an aileron on the edge of the wing, which controls the how the aircraft banks as it turns. A computer is also used to manage how the plane climbs and descends, by pitching the nose of the aircraft up and down.

In the case of the Qantas flight, one of the computers misread the position of the aircraft – in particular the position of the nose.

As a result the plane twice started descending rather than maintaining the correct position. An accident was averted by the quick action of the crew, who resumed control from the computers.

This was the most serious incident involving an A330, since a test flight crashed in June 1994, killing all seven on board. In that case an inquiry attributed the crash to pilot error.

The only other death linked with the A330 was on May 25 2000, when a would-be hijacker jumped from a Philippine Air Lines aircraft relying, unsuccessfully, on a home-made parachute.

Otherwise the aircraft's safety record is considered excellent with other incidents having been linked to terrorist attacks in Sri Lanka and, in the case of another Philippine air craft, an error by air traffic controllers.

[Intio]

I think it will be a challenge to recover, let alone find, the flight recorders.

I would have thought that black boxes would be equipped with some kind of bouyant safety measures in case of an ocean crash. Even if they (air bags?) have to be hidden behind protective casing to protect them before being deployed. And couldn't a black box carry some kind of low power-drain emitter to help salvage crews to its location?

I'm ignorant of how salvage operations are conducted, so perhaps I'm not taking into account the complexities involved.

[FSTargetDrone]

I would have thought that black boxes would be equipped with some kind of bouyant safety measures in case of an ocean crash. Even if they (air bags?) have to be hidden behind protective casing to protect them before being deployed. And couldn't a black box carry some kind of low power-drain emitter to help salvage crews to its location?

I'm ignorant of how salvage operations are conducted, so perhaps I'm not taking into account the complexities involved.

I don't know about the possibility of built-in flotation devices but I believe that flight recorders do have automatic beacons that are activated in the event of a catastrophic incident. The problem is that they may well be on the bottom of the ocean floor. It may be possible to retrieve them with ROVs or some such, but first you'd have to find them. I wonder how robust flight recorders are given the water pressure at depths of thousands of meters. Flight recorders are tough by design, but they aren't invulnerable.

Also, is anyone familiar with how long the batteries on these flight recorders are expected to last once the recorders starts transmitting their signals? Days? Weeks?

[tim31]

From the NTSB website:

Each recorder is equipped with an Underwater Locator Beacon (ULB) to assist in locating in the event of an overwater accident. The device called a "pinger", is activated when the recorder is immersed in water. It transmits an acoustical signal on 37.5 KHz that can be detected with a special receiver. The beacon can transmit from depths down to 14,000 feet.

Underwater locator beacon 37.5 KHz; battery has shelf life of 6 years or more, with 30-day operation capability upon activation

Noting of course that the entire airplane is supposed to be crumple zone for an FDR; if the aircraft broke up as suggested, this reduces the survivability of the unit.

[Broomstick]

Just to clarify - the actual recording units are most commonly physically located in the tail of the airplane under the theory that the nose usually hits the ground first. There are some exceptions to this, of course, but it's a good rule of thumb.

The big trick is finding the damn things. Looks like the ocean depth there is twice the reliable "ping" distance, but if they can get an ROV down low enough they might be able to pick it up.

As for potential computer problems on the A330 - far too soon to tell. Unless you're a litigation happy lawyer, of course. And, of course, one reason we still have human pilots is for just in case a flight computer goes wonky.

[FSTargetDrone]

From the NTSB website:

Thanks! Very helpful.

I think I've seen video of crashes on land where the recovered recorders were displayed and you could see that they were smashed up badly enough to crack the casing. Hitting the water may as well be hitting concrete, plus the parts sink afterward. Water currents may push the stuff all around on its way down.

Speaking of, the site of the crash site has been confirmed by the Brazilian military:

Brazil confirms Air France jet crashed in ocean

By FEDERICO ESCHER and ALAN CLENDENNING, Associated Press Writers Federico Escher And Alan Clendenning, Associated Press Writers – 7 mins ago

FERNANDO DE NORONHA, Brazil – Brazilian military planes found a 3-mile (5-kilometer) path of wreckage in the Atlantic Ocean, confirming that an Air France jet carrying 228 people crashed in the sea, Defense Minister Nelson Jobim said Tuesday. Jobim told reporters in Rio de Janeiro that the discovery "confirms that the plane went down in that area," hundreds of miles (kilometers) from the Brazilian archipelago of Fernando de Noronha.

"There isn't the slightest doubt that the debris is from the Air France plane," Jobim said.

He said the strip of wreckage included metallic and nonmetallic pieces, but did not describe them in detail. No bodies were spotted in the crash of the Airbus A330 in which all aboard are believed to have died.

The discovery came just hours after authorities announced they had found an airplane seat, an orange buoy and signs of fuel in a part of the Atlantic Ocean where ocean depths range from less than 1,610 meters (one mile) to more than 4,800 meters (three miles).

Jobim said recovery of the plane's cockpit voice and data recorders and other wreckage could be difficult because much of the wreckage sank.

"It's going to be very hard to search for it because it could be at a depth of 2,000 meters or 3,000 meters (1.2 miles to 1.8 miles) in that area of the ocean," Jobim said.

The initial discovery of wreckage announced before Jobim spoke came about 36 hours after the jet went missing as it flew from Rio de Janeiro toward Paris.

A Brazilian air force spokesman said the two spots where debris was located suggested the pilots may have tried to turn the plane around to return to Fernando de Noronha.

"The locations where the objects were found are toward the right of the point where the last signal of the plane was emitted," said the spokesman, Col. Jorge Amaral. "That suggests that it might have tried to make a turn, maybe to return to Fernando de Noronha, but that is just a hypothesis."

Amaral said some of the debris was white and small, but did not describe it in more detail.

Jobim made the announcement after two commercial ships that joined the search late Tuesday morning reached sites where the debris was found, a Navy spokeswoman said.

"Once they come across the objects, they will be analyzed to determine if they are parts of the plane or just junk," she said.

A U.S. Navy P-3C Orion surveillance plane and 21 crew members arrived in Brazil on Tuesday morning from El Salvador and was to begin overflying the zone in the afternoon, U.S. officials said in a statement. The plane can fly low over the ocean for about 12 hours at a time and has radar and sonar designed to track submarines underwater.

The French dispatched a research ship equipped with unmanned submarines to the debris site. The subs can explore depths of up to 19,600 feet (6,000 meters). The U.S. was considering contributing unmanned underwater vehicles in the search as well, according to a defense source who spoke on condition of anonymity because he was not authorized to speak on the record.

The 4-year-old plane was last heard from at 0214 GMT Monday (10:14 p.m. EDT Sunday) about four hours after it left Rio.

If no survivors are found, it would be the world's worst civil aviation disaster since the November 2001 crash of an American Airlines jetliner in the New York City borough of Queens that killed 265 people.

Investigators on both sides of the ocean are trying to determine what brought the plane down, with few clues to go on. Potential causes include violently shifting winds and hail from towering thunderheads, lightning or some combination of other factors.

The crew made no distress call before the crash, but the plane's system sent an automatic message just before it disappeared, reporting lost cabin pressure and electrical failure. The plane's cockpit and "black box" recorders could be thousands of feet (meters) below the surface.

French Prime Minister Francois Fillon said that if the debris is confirmed to be part of Flight 447, "This will allow us to better determine the search zone."

"We are in a race against the clock in extremely difficult weather conditions and in a zone where depths reach up to 7,000 meters (22,966 feet)," he told lawmakers in the lower house of French parliament Tuesday. Black box recorders can emit signals for up to 30 days.

The chance of finding survivors now "is very, very small, even nonexistent," said Jean-Louis Borloo, the French minister overseeing transportation.

The Airbus A330-200 was cruising normally at 35,000 feet (10,670 meters) and 522 mph (840 kph) just before it disappeared.

But just north of the equator, a line of towering thunderstorms loomed. Bands of extremely turbulent weather stretched across the Atlantic toward Africa.

Borloo called the A330 "one of the most reliable planes in the world" and said lightning alone, even from a fierce tropical storm, probably couldn't have brought down the plane.

"There really had to be a succession of extraordinary events to be able to explain this situation," Borloo said on RTL radio Tuesday.

France's junior minister for transport, Dominique Bussereau, said the plane sent "a kind of outburst" of automated messages just before it disappeared, "which means something serious happened, as eventually the circuits switched off."

French military spokesman Christophe Prazuck said France has three military patrol aircraft flying over the central Atlantic, but could shift its search operations closer to the site of the Brazilian discovery. He said an AWACS radar plane also had been dispatched and should join the operation on Wednesday.

French police were studying passenger lists and maintenance records, and preparing to take DNA from passengers' relatives to help identify any bodies.

French Defense Minister Herve Morin said "we have no signs so far" of terrorism, but all hypotheses must be studied.

Alain Bouillard, who led the probe into the crash of the Concorde in July 2000, was put in charge of France's accident investigation team.

President Barack Obama told French television stations the United States is ready to do everything necessary to find out what happened.

On board the flight were 61 French citizens, 58 Brazilians, 26 Germans, nine Chinese and nine Italians. A lesser number of citizens from 27 other countries also were on the passenger list.

Two Americans living in Rio de Janeiro were on board. Michael Harris, 60, a geologist, and his wife Anne, 54, were headed to Europe for work and vacation. They lived previously in Lafayette, Louisiana.

Among the passengers were three young Irish doctors, returning from a two-week vacation in Brazil. Aisling Butler's father John paid tribute to his 26-year-old daughter, from Roscrea, County Tipperary.

"She was a truly wonderful, exciting girl. She never flunked an exam in her life — nailed every one of them — and took it all in her stride," he said.

[The Duchess of Zeon]

The ocean there isn't 9,000 meters deep; the deepest part of the Atlantic is the Puerto Rico trench, well away from there, at 8,600 meters. The depth in the area is, as the later article noted, about 4,800 meters at most on the abyssal, so we can get research craft and ROVs down to it, though pretty extreme ones will be required. Note that the crush depth on black boxes is about 20,000 feet I believe, though that's only reached in a few tiny abyssals in terms of surface area. Charmingly, if you look at a topographic map of the craked and layered bottom of the Atlantic, 400 miles northeast of Fernando de Noronha is one of the more prominent Atlantic features of two mountain ranges bracketing a trench (they look like crumple zones and are a prominent subsurface feature in the Atlantic), and if the black boxes had the misfortune to be dumped into that trench, which I believe is 7,000 meters deep offhand, their crush depth might have been exceeded. On the other hand, those uplifts reach a mere 1,600 meters below the surface where recovery would be much easier. We'll see.

Edit: The feature in question is called the Romanche Trench and is up to 7,760 meters deep. It's part of the Romanche Fracture Zone and is part of an active fracture boundary. The Trench is 300km long, 19 km wide, and is an important circulatory feature with water flow of 4 x 10^6 cubic meters per second running from west to east, which would carry any falling material from the aircraft very distant from the crash site.

[Broomstick]

Even if crush depth is exceeded it may still be possible to retrieve information as black boxes are infamously overengineered in order to survive crashes. It wouldn't be the first time one exceeded requirements. Also, while the crush depth might destroy the mechanism of the box I wonder if some forms of data storage might survive it?

[The Duchess of Zeon]

Even if crush depth is exceeded it may still be possible to retrieve information as black boxes are infamously overengineered in order to survive crashes. It wouldn't be the first time one exceeded requirements. Also, while the crush depth might destroy the mechanism of the box I wonder if some forms of data storage might survive it?

Uhm, we're talking about pressures noticeably in excess of 76 megapascals, Broomstick (11 - 12,000 psi). Also, the effects of exceeding crush depth are incredibly brutal, there's been submarines we've found afterwards where pretty much the only thing left larger than a razor blade was the reactor vessel. The tiny little chunks of black box would be crushed flatter than a piece of paper if it exceeded crush depth that far down. The fact that black boxes are apparently engineered to survive up to 60 megapascals is impressive enough as it is.

[Broomstick]

I meant if crush depth was somewhat exceeded, not that you dumped it into the deepest, darkest Atlantic trench available. Even when damaged useful data has been recovered from far less sophisticated FDR's and CVR's. Exceeding crush depth is not like throwing a switch once an arbitrary depth is exceeded - how bad it would be would, of course, depend on the final depth but no matter how deep there is still merit to attempting to recover those boxes. They don't survive 60 megapascals intact then smash into oblivion at 61. If nothing else, some information on how they can fail might be obtained, which is a pretty rare event. Such information usually leads to even better engineered black boxes.

[The Duchess of Zeon]

I meant if crush depth was somewhat exceeded, not that you dumped it into the deepest, darkest Atlantic trench available. Even when damaged useful data has been recovered from far less sophisticated FDR's and CVR's. Exceeding crush depth is not like throwing a switch once an arbitrary depth is exceeded - how bad it would be would, of course, depend on the final depth but no matter how deep there is still merit to attempting to recover those boxes. They don't survive 60 megapascals intact then smash into oblivion at 61. If nothing else, some information on how they can fail might be obtained, which is a pretty rare event. Such information usually leads to even better engineered black boxes.

Actually it is like throwing a switch when the depth is reached, Broomstick, because it means exceeding the capability of the material in question to resist the pressure, which then fractures within times mesurable usually in microseconds with enough force that even if the stuff inside could resist the pressure on its own (which it can't), the force of the container it's in being shattered would probably destroy it. If you put something whose maximum sustainable crush depth is 20,000 feet, below that level, it won't exist.

Mind you, the crush depth would include a margin of error based on possible materials variation and simple uncertainty, so it's possible if we're lucky it could survive at a greater depth, but not at the bottom of the Romanche Trench.

To try and help you understand this better, 101 kilopascals is 1 atmosphere--pressure at sea level. 76 megapascals is therefore about 752 atmospheres.

And as the French Premier noted, the crash occurred over what it is, in fact, the third deepest trench in the Atlantic.

[Broomstick]

I am NOT saying it's at the bottom of the Romanche Trench!

Get that brainbug out of your head.

Because of the tendency of aviation equipment to exceed engineering requirements no, you shouldn't expect the black boxes to implode the very second they drop below the internationally required "must tolerate down to here" line. In order to make a device that reliably meets standards it must be built to better than those standards. If they're engineered to resist 60 megapascals they can probably survive 61. I have no idea of the margin for error in that design requirement, but I fail to see why a device intended to be the very last thing destroyed in a crash/fire/disaster wouldn't exceed the requirements listed on paper to some degree or another.

Clearly, some luck would be required and there is a maximum depth below which it would unquestionably be destroyed. What I'm saying is that if was designed to last down to 20,000 feet it will almost certainly still endure 20,001. Likely 20,002 as well. The point at which it goes >poof< will almost certainly be lower that the required number. That's the way stuff is built in aviation.

[FSTargetDrone]

The ocean there isn't 9,000 meters deep; the deepest part of the Atlantic is the Puerto Rico trench, well away from there, at 8,600 meters.

Noted. That 9000 meter depth came from a "Brazilian aircraft commander and chief pilot Douglas Ferreira Machado" as quoted on Bild.de. I think it may have been mistakenly repeated elsewhere.

[The Duchess of Zeon]

I'll add that, yeah, if there's a failure along the weld lines it's possible for the object to fill with water before it is completely crushed and that might happen, but in that case all of the data is going to be exposed to sea water and we can definitely bet that the sonar beacon will cease functioning (as it in fact ceases functioning long before the crush depth is reached). Furthermore only solid-state data storage will have any chance at all of surviving that kind of immersion. The black box itself is designed for sea water immersion, but the actual recording media? That is rather different.

And of course the extremely high standards demanded of FDRs may ironically doom it by preventing an initial limited failure.

[The Duchess of Zeon]

I am NOT saying it's at the bottom of the Romanche Trench!

Get that brainbug out of your head.

Because of the tendency of aviation equipment to exceed engineering requirements no, you shouldn't expect the black boxes to implode the very second they drop below the internationally required "must tolerate down to here" line. In order to make a device that reliably meets standards it must be built to better than those standards. If they're engineered to resist 60 megapascals they can probably survive 61. I have no idea of the margin for error in that design requirement, but I fail to see why a device intended to be the very last thing destroyed in a crash/fire/disaster wouldn't exceed the requirements listed on paper to some degree or another.

Clearly, some luck would be required and there is a maximum depth below which it would unquestionably be destroyed. What I'm saying is that if was designed to last down to 20,000 feet it will almost certainly still endure 20,001. Likely 20,002 as well. The point at which it goes >poof< will almost certainly be lower that the required number. That's the way stuff is built in aviation.

I already observed the margin of error in my posts. You're the one who said that the crush depth is something that is survivable for the black box, and to a degree that's theoretically possible, especially if it's been deliberately designed so that one small portion fails, and I don't know if that's the case, allowing it to flood before the black box completely collapses.

I love how you're lecturing me as though aviation is some kind of super-sophisticated field and marine engineering isn't. I KNOW that tolerances have errors, conservative ones, for precisely the reasons you describe, and that's the case in all engineering disciplines. Christ. I don't need any lectures from a private pilot to know about how materials fail under pressure.

It is however simply a fact that IF crush depth was exceeded--and you completely ignored that point!--the data is almost certainly not being recovered. Hell, the transponder will stop functioning at 14,000 feet, not 20,000 feet, which makes it even more likely we'll just never find it, when you factor in the current in that trench I mentioned, so even if it doesn't reach the bottom it could be carried along for quite some distance from the wreck.

There's a reason the French are moving so fast to find it, because it's probably dozens of kilometers or even more from the crash site, and it's possibly broken and being exposed to sustained sea water at best--if it isn't smashed into razor blades, that is.

But I was explaining what crush depth was, and in a strict sense, crush depth should be where it shatters into a million pieces. It's actually due to imperfect tolerances in material--some welds being weaker than others--that we get more coherent and larger debris fields from situations where a vehicle or object exceeds crush depth. Because of that, it's more likely for large objects to have intact features after an implosion on exceeding crush depth, not small ones.

[The Duchess of Zeon]

Oh, and while I'm at it, Broomie, consider the fact that only a relatively tiny part of the world's oceans exceeds 6,000 meters in depth. They just had the bad luck to go down very close (and perhaps right over) such an area, so the possibility was raised. They are maybe not in the Romanche trench, hopefully they are not, though the current might nonetheless carry the black boxes into it on the descent. But this at the extreme limits of our ability to recover them, even if they're intact; there is not much designed to operate that deep, precisely because the need to do so is extremely rare.

[Broomstick]

I'll add that, yeah, if there's a failure along the weld lines it's possible for the object to fill with water before it is completely crushed and that might happen, but in that case all of the data is going to be exposed to sea water and we can definitely bet that the sonar beacon will cease functioning (as it in fact ceases functioning long before the crush depth is reached). Furthermore only solid-state data storage will have any chance at all of surviving that kind of immersion. The black box itself is designed for sea water immersion, but the actual recording media? That is rather different.

And of course the extremely high standards demanded of FDRs may ironically doom it by preventing an initial limited failure.

Hon, you don't understand how these things are made.

First of all, the locator beacon designed to ping through seawater doesn't start operating until it gets wet. It is DESIGNED to be immersed in water, if it isn't, the pinger doesn't ping! And the pinger, as part of the design requirements, has to keep functioning until at least crush depth. The stated "crush depth" is a minimum requirement, not a maximum.

Also, the FDR and CVR are not hermetically sealed and also for the past decade or so (well within the construction date of this airplane) they've been using solid state data storage. In fact, older airplanes are being retrofitted with the new version of the boxes which, like anything else, must be maintained and periodically updated. In fact, the older versions are no longer being made, so any new black box installed today will have solid state memory.

Yes, the recording media is, in fact, designed withstand salt water. That, too, is a requirement and it's why, when we have retrieved these boxes from underwater wreckage, we've been able to obtain data from them. The boxes are designed to admit water when submerged, and even if they weren't rupture of the exterior is so common in crashes that the interiors must be able to resist water. Here are some post crash examples:

The data storage medium in this one survived intact despite damage to the exterior. Retrieved by ROV off the coast of Alaska.


Here's another one - post retrieval they're usually transported in the water in which they are found to keep the recorder's environment as stable as possible.


Key thing to remember here is that only the data has to survive the accident - the outer shell and interfaces with the airplane can all be totally destroyed, it doesn't matter, as long as the data remains safe on whatever media it is recorded on.

Note that the "CSMU" is the interior portion where the data is protected:

Current regulations require the black boxes to survive an impact of 3,400 g's for up to 6.5 milliseconds. This rapid deceleration is equivalent to slowing from a speed of 310 miles per hour (500 km/h) to a complete stop in a distance of just 18 inches (45 cm). This requirement is tested by firing the CSMU from an air cannon to demonstrate the device can withstand an impact force at least 3,400 times its own weight. The black boxes must also survive a penetration test during which a steel pin dropped from a height of 10 ft (3 m) impacts the CSMU at its most vulnerable point with a force of 500 pounds (2,225 N). In addition, a static crush test is conducted to demonstrate that all sides of the CSMU can withstand a pressure of 5,000 pounds per square inch (350 kg/cm²) for five minutes. The fire resistance of the CSMU is further tested by exposing it to a temperature of 2,000°F (1,100°C) for up to an hour. The device is also required to survive after lying in smoldering wreckage for ten hours at a temperature of 500°F (260°C). Other requirements specify survivability limits when immersed in liquids. The CSMU must endure the water pressure found at an ocean depth of 20,000 ft (6,100 m), and a deep-sea submersion test is conducted for 24 hours. Another saltwater submersion test lasting 30 days demonstrates both the survivability of the CSMU and the function of an Underwater Locator Beacon (ULB), or "pinger," that emits an ultrasonic signal once a second when immersed in water. These signals can be transmitted as deep 14,000 ft (4,270 m) and are detectable by sonar to help locate the recorders. A final series of tests includes submerging the CSMU in various fluids like jet fuel and fire extinguishing chemicals to verify the device can withstand the corrosive effects of such liquids.

[Broomstick]

I already observed the margin of error in my posts. You're the one who said that the crush depth is something that is survivable for the black box, and to a degree that's theoretically possible, especially if it's been deliberately designed so that one small portion fails, and I don't know if that's the case, allowing it to flood before the black box completely collapses.

Well, that's where your general engineering knowledge fails and my aviation knowledge takes over. YES, they are designed to flood when immersed in water.

I love how you're lecturing me as though aviation is some kind of super-sophisticated field and marine engineering isn't. I KNOW that tolerances have errors, conservative ones, for precisely the reasons you describe, and that's the case in all engineering disciplines. Christ. I don't need any lectures from a private pilot to know about how materials fail under pressure.

I don't need a lecture from someone who is still in engineering school about something I learned in basic flight school prior to getting my license. Let's not start an educational credential throw-down here. Just because you have SOME engineering knowledge does not mean you have ALL engineering knowledge. Hell, this this stuff you can look up on the fucking internet, you don't need an engineering degree to access it.

Seriously, what did you do here? Rely on reporting from the BBC or CNN for your information regarding black boxes?

Hell, the transponder will stop functioning at 14,000 feet, not 20,000 feet,

Incorrect. It will only reliably transmist through 14,000 feet of seawater. It is designed to survive to crush depth. ROV's lowered 6,000 feet down should be able to pick up the signal for 30 days.

which makes it even more likely we'll just never find it, when you factor in the current in that trench I mentioned, so even if it doesn't reach the bottom it could be carried along for quite some distance from the wreck.

If there is a steady current it may be possible to locate the debris field downstream. It is a difficult problem, not an impossible one.

There's a reason the French are moving so fast to find it, because it's probably dozens of kilometers or even more from the crash site, and it's possibly broken and being exposed to sustained sea water at best--if it isn't smashed into razor blades, that is.

So fucking what if it's in seawater? It will operate in sea water for 30 days. Assuming the data media is intact the data will also be intact 30 days from now. At least. Probably longer, the box just won't be transmitting it's location anymore.

But I was explaining what crush depth was, and in a strict sense, crush depth should be where it shatters into a million pieces. It's actually due to imperfect tolerances in material--some welds being weaker than others--that we get more coherent and larger debris fields from situations where a vehicle or object exceeds crush depth.

The exterior welds on the box don't matter. That's not what protects the data unit.

[The Duchess of Zeon]

I've flown private aircraft before myself, thank you very much, and I didn't learn anything at all about the depth at which an FDR will continue to function from it. I don't dispute that they continue to function when immersed in sea water, that isn't the point at hand, it's when the interior is immersed in sea water at extreme depth. Now, here's the question I have--if there is a maximum depth at which it will most likely cease to function, then how does it completely fill with water in such a way as to make pressure irrelevant? Because if the pressure is equalized between the interior and the exterior by the admission of sea water, then it should continue to function regardless of depth unless the recording device itself is subject to damage from greater pressure. Which happens to have been my original point, that the data may not be recoverable due to the depth in the area.

[The Duchess of Zeon]

I don't interpret "transmitted as deep as 14,000 feet" to mean they only have a range of 14,000 feet. They would have said "range through water of 14,000 feet" if that's the case. Transmission depth implies to me a cessation of transmission at 14,000 feet.

Furthermore, you're ignoring the fact that my points remain relevant whether or not it's the exterior welds that failure, or the mechanism by which the internal data recording mechanism is constructed which fails. There would not be a stated depth at which the black box will cease to operate, unless there was some reason to believe that greater depths would, in fact, cause it to cease to operate. If the black box is designed so that the data storage components are always equalized in pressure to the sea water outside of said components, then there would be no depth at which the black box would cease to operate. Ergo, there must be some part of the black box crucial to its function, which will fail under a pressure in excession of 60 megapascals.

That is simple logic, which you are ignoring.

And that fact, that the black box has a depth at which it will be lost, is stated in YOUR posts as well as mine, and is therefore not a subject for debate--you have already conceded it. Now it is your job, not mine, to show why "endure the water pressure at 6,100 meters" somehow means that the all of the black box components are equalized to the outside water pressure, at which point that statement would be irrelevant to its function, and its inclusion nonsensical.