FDR Readout

Hi there.

Well, since working in airline industry, my Symbian journey is stagnant. I really like it though. It is because, creating application using Symbian compatible mobile device, the limit is the sky. Hehe, yes i mean it.

Now, been working closely with Flight Data Recorder System, I have some knowledge on communication structure used on aircraft. In essence, it has so many sensors around its body. For example, it has accelerometer sensor, attitude sensor, velocity sensor, ect. Why do we need these all? Well, for a reason, aircraft automatic flight control needs it for their feedback system. By acquiring aircraft attitude, the control system can decide wether the aircraft bahaves correctly or not while maintaining it.

Ok. The values sensed by sensors then acquired by a so called Flight Data Acquisition Unit (FDAU) or something like that. By FDAU, all the values is then encoded with ARINC 717 specification before sending it to FDR (some people may say it as blackbox, eventhough the color of FDR is orange).

So, it's now the important part: the collected flight data is now encoded in FDR. But how can we decode it? How can we able to view all or certain flight history, such as altitude, velocity, or attitude?

Well, I would answer it with... you need to read the ARINC 717 specification. All you need to know before able to read/decode FDR raw data is in it. I, for a couple of weeks also try to be able to read this FDR raw data.

This time, because of its nature and for some personal preferences, I chose Matlab as my development tool. It is basically pretty simple. There is one main Matlab function that is the crux of this script, i.e.:

fread(rawId,bitLen,nBit)

For this purpose, set bitLen to 1 (integer) and nBit to ubit1 (string).

From there, you can choose whatever scheme you would like to obtain, to re-structure, and to convert the value. Oh yes, I forget to tell you that because the FDR raw data is encoded in binary format, able to understand ARINC 717 is not enough. There is also a so called Interface Control Document which describe where -let say the sensed accelerometer is stored by FDAU in a dataframe. I think I'm gonna describe it later on different article. Please read the ARINC 717 specification for definition of this dataframe.

Okay, i think it's enough for now. Gotta do something else. Should you have any related discussion, please email me or comment this article.