AAL77 FDR Partial Decoder

This program decodes the uncompressed parts of the raw Flight Data Recorder (FDR commonly called "black box") file for American Airlines Flight 77 (AAL77) included by the US National Transport Safety Board (NTSB) on CDROMs provided in response to FOIA (Freedom of Information Act) requests for information regarding the events of September 11th 2001.

The program allows you to
selectively decode uncompressed parts of the FDR file and generate a Comma Separated Value (CSV) file containing the selected information. The first line of the CSV file contains the parameter names and it can be opened by various programs including Microsoft Excel and Microsoft Access. Up to 4 subframes of uncompressed data is generated in the file each time the FDR is started up which I believe happens when the engines are started. After that, data is stored in a compressed form which this program can not decode (which is why I call it a partial decoder). Most of the data in the FDR file is compressed.

The method which the program uses to recognise uncompressed data is not fool proof so it attempts to decode some of the compressed data as if it were uncompressed. This shows up as lines with unusual values.

The subframes appear in the output in my best estimate of the order they were recorded. For more details see the entries for the
Block Position, Bit Offset and Flight Stream Number parameters in Notes on Parameters for the AAL77 FDR Partial Decoder.

Although the NTSB provided CSV files generated from the FDR file which were also included on the CDROMs, I have created this program to decode information not included in the NTSB CSV files.

You can download output files generated by the program from here.

As I am providing this program free of charge, it is provided as is.

I take no responsibility for what the program does or doesn't do.

However, you can email feedback to me (Warren Stutt).

You can download and install the program using Microsoft Internet Explorer from here.

A Change Log detailing the changes in different versions is available here.

There is a help page on using the program. You can also press F1 when the program is running to bring up the same help page.

In the interests of transparency in showing that the program is really generating its output from the raw FDR file, you can download the C# source code. I used Microsoft Visual C# 2005 Express Edition to create it. You can look at the .cs source files using any text editor, and you can download the Microsoft Visual C# 2008 Express Edition from Microsoft to compile it. Alternatively, you may be able to get a DVD with the Visual Studio Express Editions from your local Microsoft sales office. I have not actually checked that it does compile with the 2008 Edition.

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