It took almost a month for officials to locate the wreckage of EgyptAir flight 804, which crashed into the Mediterranean Sea last May. It took a few days more for them to recover the flight data recorder and cockpit voice recorder that were resting on the sea floor, 3,000 metres down. The devices — colloquially known as black boxes — contain the crucial evidence that investigators will use to piece together the cause of this plane crash.

In the age in which Nasa can monitor and operate a rover on Mars, tens of millions of kilometres from Earth, and smartphones can receive real-time traffic updates, why can't we track the location of commercial airliners in real time, or stream the data black boxes record back to the ground?

The idea that passengers’ families could wait months to find out what happened to their loved ones — or even more than two years, in the case of Malaysia Airlines flight MH370, still unrecovered after its crash in March of 2014 — is hard to understand.

Air-travel regulatory bodies, government agencies, and airlines are considering whether changes need to be made — and what kind. In the meantime, however, despite using old technology, the black box remains an effective — and essential — tool.

What are black boxes?

Flight data recorders are about the size of a shoebox, weigh about 10 pounds, and cost close to £15,000 apiece. They are usually located in the tail section of an aircraft to save them from the brunt of a crash impact, and are equipped with a water-activated locator beacon, which can ping for 90 days at depths up to 6,000 metres.

The US Federal Aviation Administration (FAA) requires that planes carry two devices — both called black boxes — to help investigators piece together the cause of airline crashes. The first is a flight data recorder that tracks 88 different parameters (metrics like compass heading and altitude and airspeed) over the last 25 hours of its flight history.

Why can't we track the location of commercial airliners in real time?

The FAA also requires a cockpit voice recorder, which saves the last two hours of crew conversations, as well as ambient sounds like alarms that will go off, for example, if a plane is flying too low.

“The flight data recorder will tell how an accident happened,” says Greg Marshall, vice president of global programmes for the Flight Safety Foundation, a US-based nonprofit organisation that provides safety guidance for the aviation and aerospace industries. Meanwhile, "the cockpit voice recorder will tell you why.”

These devices also cause some colour confusion: They’re not black. They’re bright orange. The “black box” moniker could have come from the fact that they’re sometimes exposed to flames, which char them black. It could be that the term references an early version from the 1930s that relied on photographic film, and thus, had to be dark inside.

It could also be a nod to the fact that nothing about the boxes themselves matters — just the data they collect.

Building near-indstructable data treasure troves

Each flight data recorder is packed with information-slurping hardware encased in an armoured body. Sensors throughout the airplane’s fuselage accumulate data and send it along to a middleman device called the flight data acquisition unit, which routes it to the flight data recorder. Once there, the information is stored in stacked arrays of memory chips that can hold terabytes of data.

Cockpit voice recorders work similarly. Microphones in the cockpit — in the pilots’ headsets, and one to pick up those ambient sounds — record audio, then send it along to the cockpit voice recorder, which stores it in the same kind of memory chips. And it’s on those memory chips that the most valuable data about a crashed aircraft’s fate resides.

[The black box] is designed to withstand... an hour in an 1100-degree Celsius inferno.

Black boxes are engineered to protect their brains — the memory boards that hold the data — so they are encased in aluminium, then an inch-thick layer of insulation that can withstand high temperatures, and finally, an outer casing of titanium or stainless steel. That whole package, known as the crash survivable memory unit, is subjected to rigorous testing.

Because it must be able to survive a violent and fiery plane crash, it is designed to withstand crash impacts of 3,400Gs (or 3,400 times the force of gravity), as well as an hour in an 1,100-degree Celsius inferno. They’re engineered to endure 30 days in salt water, a soaking in jet fuel, and five minutes under 5,000 pounds per square inch of force. And finally, manufacturers load a steel pin with a 500-pound weight behind it ten feet above the box, then drop it to test the resiliency of the metal casing. The rest of the black box — including the power supply and circuit boards — doesn’t have the same protections and may well be destroyed in a crash.

All that protection means that black boxes are recovered and useful much more often than not, which is why the technology has endured for so long.

Black boxes' urgent creation

Nearly six decades ago, a need to collect data and information from flights appeared, as air travel became more common.

“If you go back to the early days before flight recorders, the causes of some accidents could be theorised but not really known,” Marshall says. “Today, the voluminous amount of information they capture is absolutely vital to investigators. It assists them in speeding up investigations, helps them to identify contributing factors, and it allows regulators to very rapidly affect change.”

Flight data recorders have changed quite a bit since the United States first required them in large civilian passenger aircraft in 1958, after a series of accidents involving the de Havilland Comet, the first production commercial jetliner.

Over time, the jetliner’s fuselage couldn’t handle the changes in pressure throughout the cycle of a flight, and the planes broke apart in midair, killing everyone aboard. British authorities were able to determine the cause of the accidents conducting tests on intact jetliner hulls, but the high-profile accidents made it clear that more information was necessary.

The voluminous amount of information they capture is absolutely vital to investigators.

Early flight recorders took down just five parameters — compass heading, altitude, airspeed, time, and vertical acceleration — via markings on metal foil. By the 1960s, the US government required the addition of cockpit voice recorders, and in that era, both devices captured information on magnetic tape. As digital aviation electronics took over in the 1980s, it became feasible to collect more information than ever before, but storage was an issue. The introduction of the more resilient solid state recorders — the recorders that store data on stacked arrays of memory chips — made it possible to accumulate far more data. They are also much harder to damage, because unlike the recorders that came before them, they have no moving parts.

Thirty years or so later, technology has evolved at warp speed, but we’re still in the solid-state recorder era, and they still have to be located and recovered from crash sites.

What they do well

There are rare cases where black boxes are lost or destroyed. In addition to the still-missing Malaysian Airlines flight MH370, the recorders belonging to the two planes that struck New York’s World Trade Center on 11 Sept 2001 were never recovered.

“It’s certainly an anomaly for our investigations,” says Sarah McComb, chief of the vehicle recorder division for the National Transportation Safety Board, the US agency that investigates airline crashes. “And it’s rare to find them and not be able to access the data, unless it’s an old type of recorder.”

Sometimes, the information stored on the recorders makes it clear very quickly what happened.

When Germanwings flight 9525 crashed in the French Alps in March 2015, the flight data recorder revealed that the person behind the controls purposefully began to descend and increase speed before impact. Meanwhile, the voice recorder actually picked up audio of the pilot banging on the cockpit door and saying, “For God’s sake, open the door!” as passengers screamed in the background. Investigators had the information they needed to conclude that copilot Andreas Lubitz had locked the pilot out of the cockpit and purposefully crashed the plane.

Safety advocates are arguing for more.

Still, these recorders are ‘90s-era technology.

And though — much like a smartphone — solid state memory recorders have evolved to be able to store more and more information, there are alternatives to consider.

Some military aircraft use recorders encased in buoyant shells that will physically eject from planes at the moment of impact. Even if the wreckage hits the ocean floor, the recorder will not.

Though airlines are already streaming some maintenance and location data back to the ground, some safety advocates are arguing for more. And, perhaps most controversially, some groups are pushing for the addition of cockpit surveillance video.

“The recorders that we have now have been very effective,” McComb says. “But we continue to make recommendations in areas where we see technology is improving, including image recorders, supplemental flight data, triggered transmission of information or deployable recorders, to supplement the already very valuable data we get from flight recorders.”

Why don't we switch to something more hi-tech?

Massive regulatory changes like these are complicated, expensive, and slow. After all, once a change is made, airlines have to do some combination of retrofitting and replacing their fleet. And though it’s possible to stream some data from planes right now, the sheer amount of data collected by flight recorders is immense, and satellite time and storage are both very expensive.

Some groups are pushing for the addition of cockpit surveillance video.

There are also concerns about security. Though the NTSB has been recommending the use of video recording in cockpits since the year 2000, pilots' unions have fought against adding video surveillance to flights for privacy reasons. One fear is that pilots’ families might have to endure the public release of video of their loved ones dying.

“We’re still recommending video recording, but we haven’t gotten a lot of movement,” says McComb. “The pilot community has been objecting since we first recommended them.”

For its part, the FAA says it does not have any changes underway for flight data recorders. As for tracking technology, it “continues to work with industry and our international partners on policy and guidance for advanced technologies that may be useful in aircraft accident investigations.”

But even if change is coming slowly, it does appear that it’s coming. The Canada-based International Civil Aviation Organization (ICAO), an arm of the United Nations, adopted new amendments in March that require flight data recorder information to be quickly and easily retrievable post-crash. At the end of last year, it passed additional amendments, mandating that airlines must be able to track their aircraft at 15-minute intervals during normal operations by 2018, and at 1-minute intervals in distress situations by 2021.

Though ICAO is not a regulatory body, its member governments do develop regulations that comply with their standards and recommended practices.

Some airlines and manufacturers have also started making moves on their own. Qatar Airlines said earlier this year that it plans to implement a system to transmit data to its ground operations, and there are tech companies that offer aftermarket retrofits for existing planes. In 2015, French aircraft manufacturer Airbus said it has been in talks with the European Aviation Safety Agency to push for the approval of ejectable recorders.

Still, it’s a safe bet that the black box will be with us for some time.

As long as they remain durable and findable even in the deepest depths or craggiest mountains — and as long as they keep capturing vital information that gives investigators the clues they need — these tiny, data-filled boxes might not go anywhere.

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