PPRuNe Forums - View Single Post - Air Asia Indonesia Lost Contact from Surabaya to Singapore
Old 15th Jan 2015, 13:43
  #2068 (permalink)  
Mad (Flt) Scientist
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,127
Originally Posted by Gysbreght View Post
The DFDR memory module contains a long string of 0’s and 1’s, called “bits”. Twelve bits comprise a “word”, many words are contained in a 1-second “subframe”, 4 subframes form a “frame”. The meaning of the thousands of words in a frame is defined in a “Decoding Document” that is submitted to the authorities when an airplane obtains it registration. The first word in each subframe contains the date and time of the subframe. Each of the subsequent words is dedicated to one or more of the thousands of parameters recorded.
In addition, before you can get to those 1s and 0s, you need to decompress the data, which is stored in a special and proprietary format which compacts the data to be able to store as much as possible in as small memory as possible.

The decoding document above is basically an OEM thing, but the FDR manufacturer is the one who knows how it's compressed. that's another set of special software required, with the right decoding info too.

I believe the 9/11 truthers have been trying for 12+ years to decode one of the "raw" FDR files from one of the aircraft that they somehow acquired, with no success because no-one who knows how to do it - which is a pretty closed community - has any interest in providing the information required. In this case, it's won't be the same reluctance, but it's a bit of an art, so if you've never done it before, even with the right info it might take a while ...
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