TripleBravo;
Quote:
I'm not sure anyone will ever know. I'm not aware of any data on the FDR that will tell.
That should be an easy one, if you have the DFDR data (and the coordinates of the runway). LON / LAT is recorded, the air / ground state as well as radio alt, so that you can determine the position where the aircraft settled within GPS precision (limited by the time step interval of the recording and the precision of the aircraft's transducers).
The DFDR lat/long parameters in and of themselves are not sufficiently accurate to determine the touchdown point. Lat/Long are normally supplied by the IRS's and as you know, position is determined by DME/DME etc and a bias is supplied to the IRS's, (the IRS's actually never are "updated" themselves).
The only way that a touchdown point can be determined with any accuracy is if the aircraft had GPS and the DFDR dataframe was sufficiently sophisticated to capture these parameters. Even thought the Airbus 320 DFDR is a good one, not all DFDRs capture huge amounts of data. FOQA/FDA recorders typically capture up to four times the amount of data that the DFDR does and often at higher sample rates. Even if this aircraft were fitted with such a second recording system however, it would not have survived the crash as the FDIMU/FDAU (whatever is installed) is in the EE compartment.
The parameters which are typically used to determine the touchdown point are VACC, (vertical acceleration), main gear oleo compression, IVSI all of which are combined in an analysis by flight data software to determine the point of first touchdown. You are correct in observing that this determination is only as accurate as the sample rate, typically once-per-second and that critical information can be missing in such a slow rate. VACC is typically sampled at eight times per second as are the oleo compression parameters but this is less the case with many DFDRs. I suspect this DFDR samples these parameters at these higher rates however. Both interpretation and interpolation are crucial aspects of this kind of analysis and so the process is not as "direct" or straightforward as it may first seem.
The other way touchdown point might (emphasize might) be determined is to animate the approach, path on the runway and excursion to the left. The wind vector is known and other basic parameters can be sufficient to provide a very good although elementary animation even with a slight glidepath duck-under. The process may or may not yield accurate information depending upon a number of factors but it can be done. I think the airport video is probably too blurred to be of accurate use.
PJ2