Role of black boxes in airplane crash investigations

These boxes will help investigators find the crucial events that led to the crash, which killed over 62 people on board

In a significant development towards ascertaining the reasons behind the Sriwijaya Air’s flight SJ182 flight crash in Indonesia on Saturday, investigators have located the “black boxes” of the ill-fated aircraft. These boxes will help investigators find the crucial events that led to the crash, which killed over 62 people on board. Let’s read in detail how this component is important…

Black boxes

The black boxes, which are actually two orange metallic boxes containing the recorders, date back to the early 1950s, when, following plane crashes, investigators were unable to arrive a conclusive cause for the accidents and deemed it necessary to install the said recorders on aircraft. In the initial days of the black box, the information was recorded on to a metal strip, which was then upgraded to magnetic drives succeeded by solid state memory chips.

Helpful in investigation

Most aircraft are required to be equipped with two black boxes — the cockpit voice recorder (CVR) and the flight data recorder (FDR) — that record the information about a flight and help reconstruct the events leading to an aircraft accident. While the CVR records radio transmissions and other sounds in the cockpit such as conversations between the pilots and engine noises, the flight data recorder records more than 80 different types of information such as altitude, airspeed, flight heading, vertical acceleration, pitch, roll, autopilot status etc.

Device survives the crash

The recording devices are stored inside a unit that is generally made out of strong substances such as steel or titanium and are also insulated from factors such as extreme heat, cold or wetness. To protect these black boxes, they are equipped towards the tail end of the aircraft – where usually the impact of a crash is the least. There have been cases where planes have crashed into water bodies. To make black boxes discoverable in situations where they are under water, they are equipped with a beacon that sends out ultrasound signals for 30 days.

Analysis of black boxes

It usually takes at least 10-15 days to analyse the data recovered from the black boxes. Meanwhile the investigators will be looking for other clues such as taking accounts from air traffic control personnel and recordings of the conversation between ATC and the pilots moments before the crash.

Flight recorders

CVR

Cockpit Voice Recorder records conversations between crew members
and with air traffic control

2 hours of recording time

Casing
1 hour at 1,100oC
1 month immersed in water at a depth of 6,000 metres

FDR
Flight Data Recorder records technical flight data including temperature, spedd, altitude and trajectory 25 hours of recording time

Underwater locator beacon

Emits ultrasonic pulse on immersion for up to 90 days.

Pinter detectible 2 km from source.

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