The information that the program uses on how each parameter is stored in the subframes is mostly from the data frame layout 757UALmap.xls with notes from D226A101-3G.pdf  that I received from this and this FOIA requests to the NTSB respectively. Parts of the data frame layout do not agree with the data actually recorded by the FDR. I have used the data frame layout except where noted below.

In versions prior to 1.4, I did not work from an official data frame layout, instead I picked out which parts of the subframe represent each parameter by looking for correlations between the binary data in the subframes and the values of the parameters in the NTSB CSV files. Starting from version 1.4 the program I have corrected the program to use the data frame layout 757UALmap.xls that I received from the NTSB except where noted below.

I have only included some parameters in this program. However there are many more listed in the NTSB's United Airlines Flight 93 FDR Report and in the data frame layout in the attachment (757UALmap.xls). Let me know if there are any more which you would like to see included.

ALTITUDE (1013.25mB)
Raw ALTITUDE (1013.25mB) COARSE
Raw ALTITUDE (1013.25mB) FINE
The conversion used in Note 3C of  D226A101-3G.pdf gives correct values and is the one I used, whereas the one in 757UALmap.xls and used in the NTSB CSV files gives incorrect values for negative values. Bear in mind that these values are uncorrected pressure altitude values that presume that the air pressure at sea level is 1013.25mB and will be different from the true altitude if the air pressure at sea level was not that value when the altitude values were recorded. I have included the raw values as a parameter in the program to allow you to do your own conversion if you wish. The equivalent Microsoft Excel formula my program uses and Note 3C of D226A101-3G.pdf uses to convert a pair of Raw Coarse and Fine Values to feet is:
     Raw Coarse Value * 128 + MOD( Raw Fine Value, 128 )

The equivalent Microsoft Excel formula 757UALmap.xls and the NTSB CSV files uses to convert a pair of Raw Coarse and Fine Values to feet is:
     Raw Coarse Value * 128 + Raw Fine Value

BLEED DUCT PRESS - R
This parameter is named BLEED DUCT PRESS - in the NTSB CSV files.

CONTROL COLUMN POSN-CAPT
CONTROL COLUMN POSN-CAPT Synchro Angle
Raw CAPT CONT COLUMN POSN
I used the negative of the conversion in Note 4D of D226A101-3G.pdf which produced the same values as in the NTSB CSV files with a maximum difference of 3 in the last decimal place. I have included the raw and Synchro Angle values as parameters in the program to allow you to do your own conversion if you wish. The formula my program uses to convert a raw value to a Synchro Angle is:
     Raw Value * 180.0 / 2048
The conversion my program uses to convert a Synchro Angle to an output value in degrees is:
    -2E-5 * S ^ 3 + 0.0005 * S ^ 2 + 0.4765 * S - 0.001 where S is the Synchro Angle.
The conversion Note 4D of D226A101-3G.pdf uses to convert a Synchro Angle to an output value in degrees is:
    2E-5 * S ^ 3 - 0.0005 * S ^ 2 - 0.4765 * S + 0.001 where S is the Synchro Angle.

CONTROL WHEEL POSN-CAPT
CONTROL WHEEL POSN-CAPT Synchro Angle
Raw CONTROL WHEEL POSN-CAPT
I used the negative of the conversion in Note 5D of D226A101-3G.pdf which produced the same values as in the NTSB CSV files with a maximum difference of 0.044 degrees. I have included the raw and Synchro Angle values as parameters in the program to allow you to do your own conversion if you wish. The formula my program uses to convert a raw value to a Synchro Angle is:
     Raw Value * 180.0 / 1024
The conversion my program uses to convert a Synchro Angle to an output value in degrees is:
    -1.75 * Synchro Angle.
The conversion Note 5D of D226A101-3G.pdf uses to convert a Synchro Angle to an output value in degrees is:
    1.75 * Synchro Angle.

ENG EPR COMMAND - L
ENG EPR LIMIT - L
ENG EPR LIMIT - R
HYD PRES - C
HYD PRES - L
HYD PRES - R
HYD SYS LO QTY - C
HYD SYS LO QTY - L
HYD SYS LO QTY - R
IDG OIL TEMP - L
REQ'D NAV PERF-(RNP)
STATIC PRESSURE
I used the location for these parameters indicated in 757UALmap.xls rather than the ones the NTSB CSV files appeared to use. This causes my program to produce different values from the NTSB CSV files for these parameters.

FL CH MODE OPER FCCL
FL CH MODE OPER FCCR
FL CH MODE OPER MCPA
FL CH MODE OPER FCCC
I have used the values "ENGA NOT" and "FL CH ENGA" as in 757UALmap.xls rather than "NOT ENG" and "ENG" as in the NTSB CSV files.

FLAP HANDLE POSN
FLAP HANDLE POSN Voltage
Raw FLAP HANDLE POSN
I used the conversion in Note 12D of D226A101-3G.pdf rather than the one the NTSB CSV files appears to use. I have included the raw and voltage values as parameters in the program to allow you to do your own conversion if you wish. The formula my program uses to convert a raw value to a voltage is:
    Raw Value * 5.0 / 1024
The conversion my program uses and Note 12D of D226A101-3G.pdf uses to convert a voltage to a value in degrees is:
    F = -4.292969 + 9.640625 * V - 7.429688 * V ^ 2 + 2.080078 * V ^ 3. If F > 15 then F = -8.527527 + 7.703903 * V where F is the value in degrees and V is the voltage.
The conversion that the NTSB CSV files appear to use to convert a raw value to degrees is:
    F = Raw Value * 15.0 / 512. If F > 15 then F = 0
The parameter in the NTSB CSV file uses 6 significant figures whereas 2 decimal places would seem more appropriate.

GPS HOURS
GPS MINUTES
GPS SECONDS
I couldn't produce sensible values for these parameters so I removed them from the program.

MAG HEADING CAPT
WIND DIRECTION TRUE
I used a conversion from raw values to degrees that produced the same values for these parameters as in the NTSB CSV files with a maximum difference of 1 in the last decimal place and with a range of 0 to 360 degrees rather than the conversions from raw values to degrees from 757UALmap.xls which produce values from -180 to 180 degrees.

MANUFACTURER CODE
The NTSB CSV Files give the single value of Honeywell for this parameter. The program gives the single value of ALLIEDSIGNAL for this parameter using Note 1F of D226A101-3G.pdf. The NTSB's United Airlines Flight 93 FDR Report says that the FDR was an Allied Signal SSFDR and that the memory board of the FDR was sent to Honeywell facilities in Redmond, Washington for evaluation and downloading.

MIN SPEED TMCL
I have used the values "INOPER" and "MIN SPEED" as in 757UALmap.xls rather than "ENGA NOT" and "MIN SPD EN" as in the NTSB CSV files.

PRES POSN
PRES POSN Data
Raw PRES POSN Data
The Most Significant (MS) data is only recorded once every 64 subframes, whereas the Least Significant (LS) Data is recorded in every subframe. I have combined these values to produce the PRES POSN LAT (DEG) and PRES POSN LONG (DEG) parameters, however since the MS and LS data are recorded at different frequencies, I have provided the option to include the uncombined MS and LS data fields. If you choose to include all subframes in the output, the first values in the PRES POSN LAT (DEG) and PRES POSN LONG (DEG) parameters will be incorrect because of these different frequencies. I have included the raw values as a parameter in the program to allow you to do your own conversion if you wish.

The formulas my program uses are:
PRES POSN LAT-LSData = Raw PRES POSN LAT-LSData *  90.0 / 131072
PRES POSN LAT-MSData = Raw PRES POSN LAT-MSData * 90.0 / 32
PRES POSN LONG-LSData = Raw PRES POSN LONG-LSData * 180.0 / 131072
PRES POSN LONG-MSData = Raw PRES POSN LONG-MSData * 180.0 / 32
PRES POSN LAT = PRES POSN LAT-MSData + PRES POSN LAT-LSData
PRES POSN LONG = PRES POSN LONG-MSData + PRES POSN LONG-LSData

R ENG BLEED OVHT
The program gives the single value of NORMAL for this parameter using 757UALmap.xls whereas the NTSB CSV Files give the single value of OVHT for this parameter. .

RUDDER PEDAL POSN
The maximum difference between the output of the program and the NTSB CSV files is 0.002 degrees.

SYNC WORD
I used a location that produced the same values as in the NTSB CSV files with a range of 0 to 3 where a value of 0 indicates subframe 1 through to a value of 3 which indicates subframe 4 rather than the location in 757UALmap.xls which produces the whole sync words.

VENDOR DATABASE CODE
The program outputs the single value of 0 for this parameter in agreement with the NTSB CSV files. However, Note 5F of D226A101-3G.pdf notes that this value should be 4.

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