Well golly gee you smart people. Let's see if we can step through it here.
Data(parameters) from around the plane arrives at the FDAU.
The FDAU is programmed with the specific details of each different parameter(data).
The FDAU syncs all this data within tolernance per type and relative time to either it's inernal or external clock which also is the Time Parameter(data) (all data is now sync'd to 'measured time' within spec tolerance) and assembles the frame.
The FDAU sends this assembly of data using the 717 frame to storage(FDR).
Now let's quote the actually specification from ARINC:
Parameters are grouped into frames according to their sample rates.
Each frame is built at its specified rate. When each frame is due, all of the member parameters are sampled, converted as necessary, and packed into the frame.
The frame is identified with a frame label and a time stamp and sent to the recorder.
Once the frame is time stamped, the amount of time taken to record it is of less concern since the time of occurrence for the data in the frame is clearly indicated by the frame time stamp.
A Frame is a time-tagged grouping of recorded parameters. Since the Frame Time Tag applies to all parameters in the frame, the amount of time that elapses while acquiring the parameters should be minimized.
Now again, your going to repeat yourself and say we can't read the raw file so the CVS file is flawed by your theory such as:
"If the data was measured at 0.3s, and recorded at 0.75s, our poor software engineer who is decoding it later will think it was measured at 0.75s."
Why would he think that? Well, you continue in your paper:
"This problem is generally solved by reserving space in the data-stream for time-stamps of the data. In other words, word 3 might be for the computed airspeed, and word 4 might be for the time-stamp that the computed airspeed was measured."
At this point, are you assuming that each parameter would have it's own word to record it's own time of measurement? Thus doubling the entire size of the frame (or halfing the available space) and removign a primary function of the FDAU.
Or do you believe the actual word used to record the Time is not relative to the other parameters in the same frame?
I know, you still want to use that footnote from my graphic to adjust the parameters time stamps. But let's look at an example of why that footnote is important and also show a demostration of proper sub-second analysis:
~~~~~~~~~~
FDR Stoppage Time
Analysis of the last seconds of recorded FDR data indicate that power to the FDAU was interrupted. The FDR lost synchronization after word 54 of subframe 3, which corresponds to a time of approximately 0125:39.8. Two words containing 1s and 0s were then recorded, followed by 27 words, most of which contained only 0s. The FDR then regained synchronization, repeating subframe 3, although with updated values. The frame counter was incremented by one, and the recording continued for another partial subframe of 22 valid words (duration of 22/64 of a second), after which the recorder stopped. It was determined that a brief power interruption to the FDAU had occurred between word 54 and the pattern of 0s. When the FDR loses signal input from the FDAU, it continues to record for up to two words (duration of 2/64 of a second), based on tests carried out by the FDR manufacturer.
The FDR will coast through a power outage of up to 400 milliseconds, during which time no recording will take place, even though the recorder is still up and running. When power was restored, a FDAU re-boot was initiated, as indicated by the 27 words of 0s (a duration of 27/64 of a second). The re-boot was considered to be a warm start, in that 0s were recorded without a resetting of the frame counter. A warm start re-boot implies a power interruption of anywhere between 10 and 400 milliseconds. The actual duration of the power interruption was not determined. However, it was most likely at least 2/64 of a second long, in order to have recorded the two non-zero words, representing a loss of FDAU signal. Therefore, following the loss of the FDAU signal, there was no recording of data for a maximum period of up to 0.37 seconds (0.4 minus 2/64).
Based on the pattern of the re-boot and the possible duration of the power interruption, the FDR stopped recording between 1.8 and 2.2 seconds after the FDAU power interruption (see above). The time of FDR stoppage would therefore be somewhere between 0125:41.6 and 0125:42.0.
~~~~~~~~~~~
Amazing good work that is there. Now I know you're going to blah blah gibberish about CSV is not FDR data, but you have yet to account for all the standards (which occur prior the CSV and eliminate these errors), plus the NTSB's (or anyone's ie FlightScape) read out software which is explicitly designed to read raw files and not screw them up when plotting them to a table or graph.
But jolly oh, you paper is a flawless victory and you should be proud of your work. I'm sure it will show up at some real Science forum where your peers will quickly award you with numerous Randi Accolades.
