Update Letter to the NTSB Dated 29th December 2010

I have now found the problem that caused the United States National Transportation Safety Board (NTSB) to decode almost 4 seconds less data in the Comma Separated Value (CSV) file they produced from the raw Flight Data Recorder (FDR commonly called "black box") file for American Airlines Flight 77 (AAL77) than my AAL77 FDR Decoder. I discussed this issue in the previous letter that I sent to the NTSB. I have found that this problem was caused by the fact that the FDR did not record Hamming Code and Page Parity Error Correcting Codes (hereafter referred to as error correcting codes) for two 128 byte pages towards the end of the FDR data.

I previously wrote a Hamming Code and Page Parity Checker for the FDR file that checks the error correcting codes. The two pages for which that program shows the error correcting codes as being incorrect are the pages where the FDR did not record the error correcting codes.

On 4th January 2011, I posted the following letter to the NTSB. An ISO image of the CDROM that I included with that letter is available here. Details of my FOIA request that I referred to are available here. I will provide an update if I receive a response.

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