Understanding the black box and why it can be so difficult to locate

By Steve Brachmann
August 26, 2015

black-box-flight-recorder-335The demise of Malaysia Airlines Flight 370 has been the most puzzling mystery affecting the aviation industry over the past year and a half. Since the aircraft’s disappearance on March 8th, 2014, there has been almost no evidence turning up which is suggestive at all of the fate of the plane and its passengers. It took until early August 2015, a full 16 months after the plane went missing, for the first pieces of confirmed debris to wash ashore. Reunion Island, the location where the MH370 wing flaperon was found, is 3,000 miles away from the search field where most of the plane is still believed to be resting, perhaps lodged in an underwater mountain found within the portion of the Southeast Indian Ridge cutting through the search field. 

This summer, we’ve been discussing a number of technologies related to disaster recovery. The massive devastation wrecked in Nepal this year by a couple of high-magnitude earthquakes was tragic but it showed that heartbeat sensors developed by NASA are helping to save lives. The massive oil spill in the Gulf of Mexico stemming from the explosion of BP’s Deepwater Horizon offshore drilling rig has resulted in a spate of oil cleanup innovations utilizing nanotechnologies and microorganisms.

Today, with the MH370 search still trudging ahead slowly, we thought that we should take some time to profile the one technology that can solve the mystery that has had investigators stumped: What made this plane not only fly wildly off course, as far as 1,000 miles by some estimates, but also fall into the Indian Ocean at all? The modern technology that has thus far evaded search teams is known by almost anyone who has ever followed news coverage of a plane crash: the “black box.”



What Is the Black Box?

There are two things to point out first when discussing the black box used to collect sensitive flight data which often unlocks the mystery behind a plane crash for investigators. First of all, the box is far from black. Black box equipment used for flight data recording is painted a bright orange and also uses reflective tape to give those looking for the flight recorder a better chance at seeing it, especially underwater. Black boxes are also provided with an underwater locator beacon that activates as soon as the unit is submerged in water, creating a pinging signal that makes it easier to find it with sonar.

Another important aspect of the black box is that we typically think of it as one component but there are actually two very different, very important pieces of technology employed in black box construction. One is a cockpit voice recorder (CVR), essentially an array of microphone sensors situated throughout the cockpit so as to record the conversations going on between pilots, co-pilots and any flight staff, as well as any communications with ground control. The other piece of equipment is the flight data recorder (FDR), which collects an incredibly vast scope of data pertaining to flight conditions. This data includes altitude, airspeed, fuel gauge, autopilot modes, right down to the movement of individual wing components.

The FDR equipment is an invention that comes to us from Australia and, as so many inventions are, is the unintended result stemming from the search to solve a different, but related, problem. In the 1950s, researchers at Australia’s Aeronautical Research Laboratory in Canberra were trying to uncover the reason why the British Comet aircraft which it had recently received was failing so often. A member of that team was chemist Dr. David Warren, who realized that the answer could be found more quickly if the research team was provided with all of the data it required, and then some. A prototype for data collection equipment was produced in 1957 and in 1960, after the unexplained crash of a Fokker Friendship craft in Queensland, the Australian government became the first in the world to require the use of black box recorders on all flights.

cockpit sound recorderWe do not have an early patent to show which details the development of FDR. However, we can go back to a U.S. patent which shows us some of the earliest developments in CVR technology. U.S. Patent No. 3,327,067, titled Cockpit Sound Recorder, was issued in June 1967 and it protected a recording assembly for an aircraft comprised of a fireproof, watertight, shockproof, sealed container, a reel-supported endless magnetic recording medium within the container, a magnetic recording head that records a signal onto the recording medium, an automatic erase head that erases recorded data from a recording medium before it passes to the magnetic recording head as well as an emergency source of electrical power. The assembly also included a means for flight crew members to erase the recorded medium after the craft lands without a problem, perhaps to give pilots more control over their cockpit privacy.

The earlier days of black box technology well behind us, the magnetic tape recording medium has since been replaced by solid state memory to record data. Today, black boxes used on aircraft regulated by the Federal Aviation Administration has to meet some exacting specifications. FDR equipment must be able to record data for 25 hours consecutively and be able to withstand extreme conditions like impacts up to 3,400 Gs and fires lasting 1 hour and reaching temperatures of 2,000°F. It can also resist water pressures at depths up to 20,000 feet. The CVR equipment must meet the same extreme condition specifications and record up to two hours of sound. Further, the black box equipment is mounted in the tail of the plane, which typically suffers last in an impact, giving the black box the best chance of survival.


Why Are We Having Trouble Finding This One?

Given the 16 months that teams have already spent searching for these flight recorders from MH370, what are the specific challenges getting in the way of finding them? As we’ve mentioned, black boxes are provided with an underwater beacon which is supposed to help crews find submerged black boxes. Pings from the beacon signals can be detected, even faintly, from hundreds of miles away. There have been naval crews tasked to search for MH370 which have been sent from five nations: America, England, China, Australia and Malaysia. Wouldn’t the ping have been picked up by now?

For one thing, it’s almost assured that the underwater beacon no longer has the battery life to keep sending its signal. Black boxes only have enough battery power to function for 30 days after it first starts sending its signals to be picked up by sonar. Making matters worse, in March of this year a report ordered by the International Civil Aviation Organization found that the battery for MH370’s underwater locator beacon was dead before the craft ever left the ground. A maintenance record error allowed the battery to go unreplaced, so search crews never had a radio signal to find, even if they were directly above the equipment. So search teams are essentially limited to what they can physically see, incredibly difficult to do in an area of the world’s oceans which has an average depth of 12,000 feet.

So far, the search has turned up an interesting assortment of sunken craft, some of which are undocumented in modern records, but not Malaysian Airlines Flight 370. Until that black box is uncovered, the secrets from this aviation mystery will never be solved. The best we can currently do is build computer models to guess what has happened, but without actual flight data those models really are just guesses. Some researchers believe that the lack of debris and oil near the supposed crash site indicate that the flight took a 90-degree nosedive into the Indian Ocean, reaching the bottom in less than a minute.


Writer’s Note: Anyone who has the stomach for it and believes that black box material might make good drama, take a look at the 2013 film Charlie Victor Romeo. It is an adaptation of a play originally produced in 1999 that dramatizes a series of CVR transcripts, giving the viewer a look into the moments leading up to emergency situations on six separate flights, some ending with fatalities, some ending without. It’s harrowing, and it’s great drama, although it may not be for the faint of heart. Netflix subscribers may still be able to find it online through that streaming video service.

The Author

Steve Brachmann

Steve Brachmann is a freelance journalist located in Buffalo, New York. He has worked professionally as a freelancer for more than a decade. He writes about technology and innovation. His work has been published by The Buffalo News, The Hamburg Sun, USAToday.com, Chron.com, Motley Fool and OpenLettersMonthly.com. Steve also provides website copy and documents for various business clients and is available for research projects and freelance work.

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