New Delhi: The 'black box' of the Mi17 helicopter, that crashed in Coonoor on Wednesday with Chief of Defence Staff (CDS) Bipin Rawat and his wife Madhulika Rawat along with other 12 officers on board, has been recovered on Thursday. Officials said that the black box was retrieved after a 23-member team carried searching operation in a radius ranging from 300 metres to 1 Km of the crash spot.
What is a black box?
All commercial flights and helicopters should mandatorily equip black boxes -- which is typically painted in orange -- that record the flight data. There are two types of black boxes Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR). Introduced in the last 1950s, black boxes are crucial in explaining the know-hows of the crash. It can record voices and flight data for up to 25 hours. According to reports, black boxes can help give inputs for 90 per cent of all crashes.
Once a crash takes place, it becomes a top priority to find out the black box as it holds pivotal clues as to what caused the flight/helicopter to go down. It records more than 3,000 parametres such as altitude, airspeed, engine performance, voice recording, etc.
How is it tested before putting it to use?
Before putting a black box into use, it is checked thoroughly to see if it can take an impact with a concrete wall at 750 kmph and a static load of 2.25 tons for at least 5 minutes, according to a report. It has the utmost crash survivability as the memory board of the recorder is surrounded by a metallic casing capable of withstanding an impact of 3,400 times of the gravity and 2,000 degrees Fahrenheit of temperature.
Dimensions and description
A black box is considerably visible with naked eyes as it possesses the dimensions of 34 cms of length and 12 cms of breadth. An FDR consists of a power supply, memory unit, controller board while a CVR comprises an underwater locator beacon, flash memory and a thermal block.
Older models recorded the data on reels of magnetic tapes or on a wire.
How to retrieve data from a black box?
The protective layers of the metallic casing has to be removed carefully and from the flash memory unit the audio, data has to be downloaded to an external device or to a drive in a computer. The downloaded files have to be decoded through various analysis methods -- mostly used is spectral analysis method, which helps in examining sounds with minimum decibels.