Team Hepher
(Reuters) – The flight data and cockpit voice recorders on the Jeju Air jet that crashed on December 29, killing 179 people, stopped recording about four minutes before it went down, South Korea’s transport ministry said on Saturday.
Here are some details about black boxes and moves to improve them.
WHAT ARE BLACK BOXES?
They are not actually black, but high visibility orange. Experts disagree on how the nickname came about, but it has become synonymous with the search for answers when planes crash.
Many historians attribute its invention to Australian scientist David Warren in the 1950s. They have evolved from early devices using wire, foil or magnetic tape to digital chips inside bright metal housings.
They are mandatory and the goal is to preserve traces of sounds and data from the cockpit to prevent future accidents, but not to establish civil or criminal liability.
There are two recorders: a cockpit voice recorder (CVR) for pilot voices or cockpit sounds and a separate flight data recorder (FDR).
More broadly, investigators say the FDR helps them analyze what happened, and the CVR can — but not always — begin to explain why. But experts warn that no two probes are the same and that almost all accidents involve multiple factors.
HOW BIG ARE THEY?
They weigh about 10 pounds (4.5 kilograms) and consist of four main parts:
* a case or interface designed to secure the device and facilitate recording and playback
* underwater locator
* core housing or ‘Crash Survivable Memory Unit’ made of stainless steel or titanium and capable of withstanding forces equivalent to 3400 times the feeling of gravity
* this case contains the recording media, which today are fingernail-sized chips on printed circuit boards.
HOW DO YOU WORK WITH RECORDERS?
Technicians remove the protective material and carefully clean the connections so as not to accidentally erase data. The audio or data file must be downloaded and copied.
The data must be decoded from the raw files before being converted into graphs.
HOW MUCH INFORMATION IS AVAILABLE?
Flight recorder capacity has been debated for years as authorities weigh improvements against cost and the risk of inadvertently creating other problems, such as draining power from other systems needed in an emergency. Cockpit monitoring has also been a touchy subject for pilot unions.
FDRs must record at least 88 bit parameters, but modern systems can typically monitor 1000 or more additional signals.
CVR normally contains two hours of loop recording, but this is extended to 25 hours.
The implementation of such regulatory changes can take years.
A series of accidents in which the recorders stopped working when the onboard power went out, including an Egyptair flight from New York to Cairo in 1999, led the US National Transportation Safety Board to recommend enough backup power for 10 minutes of extra recording.
The Federal Aviation Administration proposed the change in 2005 and it was adopted for new planes delivered starting in 2010, eight months after the 737-800 involved in the Jeju crash left the Boeing (NYSE: ) factory, according to data from FlightRadar24.
The push to extend the voice data loop to 25 hours to reflect transoceanic flights began with French recommendations after the 2009 crash of Air France 447 and accelerated after the 2014 disappearance of Malaysian MH370.
Last year, the FAA Reauthorization Act included a 25-hour cockpit voice recording requirement, echoing previous decisions in Europe.
