• A passenger jet burst into flames while landing at an airport in South Korea, killing 179 people on December 29 in one of the deadliest air disasters in that nation’s history. 

• There were only two survivors.

• The 15-year-old Boeing 737-800 jet operated by Jeju Air was arriving from Bangkok when the crash happened in the town of Muan.

• Video showed the plane skidding across the airstrip, overrunning the runway and crashing into a barrier at the airport about 290 kilometres south of Seoul. Its front landing gear apparently was not deployed.

• The pilot sent out a distress signal shortly before the plane overshot the end of the runway.

• Officials have retrieved the flight data and cockpit voice recorders of the plane’s black box, which will be examined by government experts investigating the cause of the crash and fire.

• South Korea’s acting President Choi Sang-mok has ordered an emergency safety inspection of the country’s entire airline operation system.

• Experts say many questions remain, including why the plane, powered by two CFM 56-7B26 engines, appeared to be travelling so fast and why its landing gear did not appear to be down when it skidded down the runway and into a wall.

• It may take months for investigators to complete their probe.

What is black box in an aircraft?

• The black box stores all kinds of information and conversations about the plane.

• Aircrafts are usually equipped with two boxes that record information about a flight. Both recorders are installed to help reconstruct the events leading to an aircraft accident.

• One of these, the Cockpit Voice Recorder (CVR), records radio transmissions and sounds in the cockpit, such as the pilot’s voices and engine noises. The other, Flight Data Recorder (FDR), monitors parameters such as altitude, airspeed and heading. Both recorders are installed in the most crash survivable part of the aircraft, usually the tail section.

• They are not actually black, but high-visibility orange. Experts disagree about how the nickname originated, but it has become synonymous with the quest for answers after crashes. Many historians attribute their invention to Australian scientist David Warren in the 1950s.

What are the parts of a black box?

It weighs about 4.5 kg and contain four main elements:

i) A metal chassis designed to hold the recorder and facilitate recording and playback.

ii) An underwater locator beacon to assist in locating in the event of an overwater accident. The device called a “pinger” is activated when the recorder is immersed in water.

iii) The core housing or ‘Crash Survivable Memory Unit’, made of stainless steel or titanium, and designed to withstand equivalent to 3,400 times that of gravity.

iv) Inside that housing, circuit boards holding fingernail-sized recording chips.

• The Cockpit Voice Recorder records the flight crew’s voices as well as other sounds inside the cockpit. The recorder’s “cockpit area microphone” is usually located on the overhead instrument panel between the two pilots. Communications with Air Traffic Control, automated radio weather briefings and conversation between the pilots and ground or cabin crew are recorded.

• The Flight Data Recorder onboard the aircraft records many different operating conditions of the flight. It monitors many important parameters such as time, altitude, airspeed, heading and aircraft attitude. In addition, some FDRs can record the status of more than 1,000 other in-flight characteristics that can aid in the investigation. The items monitored can be anything from flap position to auto-pilot mode or even smoke alarms.

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