By Tim Heffer
(Reuters) – South Korea's Transport Ministry said on Saturday that the flight data and cockpit voice recorders of the Jeju Air plane that crashed on December 29, killing 179 people, stopped recording about four minutes before it crashed.
Here are some details about black boxes and moves to improve them.
What are black boxes?
It's not actually black but a highly visible orange. Experts disagree on how this nickname originated, but it has become synonymous with searching for answers when planes crash.
Many historians attribute their invention to Australian scientist David Warren in the 1950s. They have evolved from early devices that used wires, chips, or magnetic tape to digital chips inside shiny metal casings.
They are mandatory and their purpose is to preserve evidence of cockpit sounds and data to help prevent future accidents, but not to determine any civil or criminal liability.
There are two types of recorders: a cockpit voice recorder (CVR) for pilot voices or cockpit sounds and a separate flight data recorder (FDR).
In general, investigators say FDR helps them analyze what happened, and CVR can — but not always — begin to explain why. But experts warn that no two investigations are the same, and almost all incidents involve multiple factors.
How big is it?
It weighs about 10 pounds (4.5 kg) and has four main parts:
* A structure or interface designed to fix the device and facilitate recording and playback
* Underwater locator beacon
* The main body or “failure memory module” is made of stainless steel or titanium and is able to withstand forces 3,400 times that of gravity
* This housing contains the recording media that are nowadays fingernail-sized chips mounted on circuit boards.
How are registrars handled?
Technicians carefully remove protective materials and clean the connections to ensure data is not accidentally erased. You must download and copy the audio or data file.
Data must be decrypted from raw files before it can be converted into graphs.
How much information is available?
The capacity of flight recorders has been a subject of debate for years, as authorities weigh improvements against the cost and the risk of inadvertently creating other problems, such as drawing power from other systems needed in emergency situations. Cockpit surveillance has also been a sensitive topic for pilots' unions.
FDRs must record at least 88 basic parameters, but modern systems can usually track an additional 1,000 or more signals.
The CVR usually has two hours of recordings in a loop but this is being extended to 25 hours.
Implementing such regulatory changes could take years.
A series of incidents in which recorders stopped working when electrical power on board was lost, including an EgyptAir flight from New York to Cairo in 1999, led the US National Transportation Safety Board to recommend sufficient backup power to provide 10 minutes of additional recording.
The FAA proposed the change in 2005 and was approved for new planes delivered starting in 2010, eight months after the 737-800 involved in the Jeju crash left the Boeing (NYSE:) plant, according to FlightRadar24 data.
The push to lengthen the voice data loop to 25 hours to reflect transoceanic flights began with French recommendations following the crash of Air France Flight 447 in 2009, and accelerated after the disappearance of Malaysian Airlines flight MH370 in 2014.
Last year, the US Federal Aviation Administration's reauthorization law included a 25-hour requirement for cockpit voice recording devices, reversing previous decisions in Europe.
