What is a black box and how do you find one? Searching for the last remains of flight MH370

These indestructible instruments have been part of air travel for decades, but what exactly do they record and why are they so hard to find?

Time is running out for the search teams hunting for the black boxes from missing Malaysia Airlines flight MH370.

These devices (known as ‘crash-survivable memory units’ in the official jargon) could hold vital information, but the batteries powering their locator beacons only lasts for around thirty days.

Once these die the black boxes will lay silent on the bottom of the ocean floor, making their discovery even more unlikely. But what exactly are search teams looking for and just what do they hope to find?

What is a black box?

Black boxes are specialized devices designed to record the final moments of a flight and survive the extreme heat and pressures of a crash. There are usually two black boxes located in the rear of the plane (usually the last point of impact) each recording a streams of information: the first, the Cockpit Voice Recorder (CVR) stores the last two hours of conversation in the cockpit, and the second,  the Flight Data Recorder (FDR) keeps a larger set of data outlining the altitude, airspeed and direction of the flight for the last 25 hours. Modern recorders include much more data – about everything from fuel levels to the position of wing flaps.

The two black boxes retrieved from the Afriqiyah Airways Airbus jet that crahsed in Libya in 2010.

What are they made out of?

The ‘crash survivable memory unit’ is actually a steel cylinder containing the memory boards that hold the actual data. This connects to the various audio compressors that feed the information into the heart of the black box. There are various layers of materials protecting these memory boards, with an outer case made out steel or titanium covering layers of dry-silica insulation (to protect against heat) and an inner aluminium housing.

How tough are they?

To test the survivability of black boxes engineers subject them to a series of tests. These include crushing the unit in various places with pressures of up to 5,000 psi (pounds per square inch), firing it down an air cannon to create impact forces of 3,400 Gs (1G is Earth’s gravity) and cooking it in a fire for one hour at a temperature of 2,000 degrees Fahrenheit. (1,100 degrees Celsius).

In order to test the units’ ability to survive in water they are also immerse in pressurized tanks of salt water for 24 hours and non-pressurized tanks for 30 days.

The undersea navy drone that will be towed behind the Australian Defence vessel Ocean Shield to try and locate the black box.

How do investigators find them?

Black boxes are painted bright orange (the actual shade is ‘international orange’) to help with visibility and are equipped with water-activated beacons that send out ultrasonic pulses when the boxes hit water. These send out a pulse every second for thirty days after activation, transmitting their signal across ranges of 14,00 feet (4,267m). Two boats are currently searching for this beacon: one, a US submarine, and the second an Australian ship, the latter towing an underwater locator behind it close to the ocean floor.

Will they find MH370’s black box?

It’s possible but seems increasingly unlikely. Flight MH370 has been compared to Air France flight 447, which went missing over an ocean in 2009 for similarly mysterious reasons. It took two years for investigators to find the flight’s black box, and even then the discovery was described as a “minor miracle”, with the device happening to land on a sandy area at the bottom of the ocean floor, rather than among mountains crags and valleys.

The FDR black box from Air France flight 447 at the bottom of the sea in 2009.

Why aren’t black boxes better?

Although you can’t really beat black boxes in terms of survivability, on the face of it there does seem to be a lot of ways they could be improved. If your smartphone can record hours of video and beam that to your computer from anywhere in the world, why can’t black boxes send out more of their information? Ejectable black boxes that float on the ocean’s surface are already in use by the US Navy, so why don’t commercial flights have those?

Professor Krishna Kavi of the University of Texas suggests that it is “sheer institutional intertia” that is holding the industry back, with pilots fearing that advanced black boxes would lead to round-the-clock monitoring of their work. Others suggest that airlines’ profits are simply so razor-thin that they don’t want to invest in a technology that hardly makes for a comforting sales pitch: ‘if you crash, at least they’ll know why!’ Incidents like the disappearance of flight MH370 might help to push the industry into action, but even then, change is likely to be slow.

Voices
The Sumatran tiger, endemic to the Indonesian island of Sumatra, is an endangered species
voicesJonathon Porritt: The wild tiger population is thought to have dropped by 97 per cent since 1900
Arts and Entertainment
Beast would strip to his underpants and take to the stage with a slogan scrawled on his bare chest whilst fans shouted “you fat bastard” at him
musicIndie music promoter was was a feature at Carter gigs
News
news
Arts and Entertainment
Story line: Susanoo slays the Yamata no Orochi serpent in the Japanese version of a myth dating back 40,000 years
arts + entsApplying the theory of evolution to the world's many mythologies
PROMOTED VIDEO
Life and Style
ebookA wonderful selection of salads, starters and mains featuring venison, grouse and other game
News
Performers dressed as Tunnocks chocolate teacakes, a renowned Scottish confectionary, perform during the opening ceremony of the 2014 Commonwealth Games at Celtic Park in Glasgow on July 23, 2014.
news
Life and Style
Popular plonk: Lambrusco is selling strong
Food + drinkNaff Seventies corner-shop staple is this year's Aperol Spritz
News
Gardai wait for the naked man, who had gone for a skinny dip in Belfast Lough
newsTwo skinny dippers threatened with inclusion on sex offenders’ register as naturists criminalised
News
Shake down: Michelle and Barack Obama bump knuckles before an election night rally in Minnesota in 2008, the 'Washington Post' called it 'the fist bump heard round the world'
newsThe pound, a.k.a. the dap, greatly improves hygiene
Arts and Entertainment
La Roux
music
Arts and Entertainment
Graham Fellows as John Shuttleworth
comedySean O'Grady joins Graham Fellows down his local Spar
News
people
News
Ross Burden pictured in 2002
people
News
Elisabeth Murdoch: The 44-year-old said she felt a responsibility to 'stand up and be counted’'
media... says Rupert Murdoch
Arts and Entertainment
tv
Extras
indybest
Sport
Arsenal signing Calum Chambers
sportGunners complete £16m transfer of Southampton youngster
Independent
Travel Shop
the manor
Up to 70% off luxury travel
on city breaks Find out more
santorini
Up to 70% off luxury travel
on chic beach resorts Find out more
sardina foodie
Up to 70% off luxury travel
on country retreats Find out more
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

ES Rentals

    iJobs Job Widget
    iJobs Gadgets & Tech

    Agile Tester

    £28000 - £30000 per annum + competitive: Progressive Recruitment: An ambitious...

    Senior SAP MM Consultant, £50,000 - £60,000, Birmingham

    £50000 - £60000 per annum + Benefits: Progressive Recruitment: Senior SAP MM C...

    SAP BW BO

    competitive: Progressive Recruitment: SAP BW BO - 6 MONTHS - LONDON London (Gr...

    Recruitment Resourcer

    £18000 - £22000 Per Annum: Clearwater People Solutions Ltd: Recruitment Resour...

    Day In a Page

    The children were playing in the street with toy guns. The air strikes were tragically real

    The air strikes were tragically real

    The children were playing in the street with toy guns
    Boozy, ignorant, intolerant, but very polite – The British, as others see us

    Britain as others see us

    Boozy, ignorant, intolerant, but very polite
    Countries that don’t survey their tigers risk losing them altogether

    Countries that don’t survey their tigers risk losing them

    Jonathon Porritt sounds the alarm
    How did our legends really begin?

    How did our legends really begin?

    Applying the theory of evolution to the world's many mythologies
    Watch out: Lambrusco is back on the menu

    Lambrusco is back on the menu

    Naff Seventies corner-shop staple is this year's Aperol Spritz
    A new Russian revolution: Cracks start to appear in Putin’s Kremlin power bloc

    A new Russian revolution

    Cracks start to appear in Putin’s Kremlin power bloc
    Eugene de Kock: Apartheid’s sadistic killer that his country cannot forgive

    Apartheid’s sadistic killer that his country cannot forgive

    The debate rages in South Africa over whether Eugene de Kock should ever be released from jail
    Standing my ground: If sitting is bad for your health, what happens when you stay on your feet for a whole month?

    Standing my ground

    If sitting is bad for your health, what happens when you stay on your feet for a whole month?
    Commonwealth Games 2014: Dai Greene prays for chance to rebuild after injury agony

    Greene prays for chance to rebuild after injury agony

    Welsh hurdler was World, European and Commonwealth champion, but then the injuries crept in
    Israel-Gaza conflict: Secret report helps Israelis to hide facts

    Patrick Cockburn: Secret report helps Israel to hide facts

    The slickness of Israel's spokesmen is rooted in directions set down by pollster Frank Luntz
    The man who dared to go on holiday

    The man who dared to go on holiday

    New York's mayor has taken a vacation - in a nation that has still to enforce paid leave, it caused quite a stir, reports Rupert Cornwell
    Best comedians: How the professionals go about their funny business, from Sarah Millican to Marcus Brigstocke

    Best comedians: How the professionals go about their funny business

    For all those wanting to know how stand-ups keep standing, here are some of the best moments
    The Guest List 2014: Forget the Man Booker longlist, Literary Editor Katy Guest offers her alternative picks

    The Guest List 2014

    Forget the Man Booker longlist, Literary Editor Katy Guest offers her alternative picks
    Jokes on Hollywood: 'With comedy film audiences shrinking, it’s time to move on'

    Jokes on Hollywood

    With comedy film audiences shrinking, it’s time to move on