Originally posted by Pilgrum
The first decode of this data independant of NTSB was done in association with PFT members somewhat secretly ... 'readout2'
That particular decoding must have revealed the existance of the extra (incomplete) packet at the end of the raw file consisting of the altitude data
we're discussing here now.
Yes, it's true members of P4T callobrated with ARINC and Boeing reps to
decode the .fdr file. The original decode "readout2" initially showed data
beyond the last full frame, however I do not know the details as to "what
was seen", or "valid".
A member of P4T by the name of "Undertow" has all the details if you would
like to contact him directly.
Have you acknowledged that data prior to W Stutts's decode and revelation of it and, if not, why?
I don't believe anyone has acknowledged this extra data; at least not to
The reason it is not important (answer to your 'why') is because the
Pressure Altitude still shows too high to hit light poles.
The RADAR Alt. analysis along with the other supporting parameters also
shows trends of the aircraft being too high.
When you view the data parameters as a whole, and study the trends with
respect to the aircraft's position you can understand the behaviour of the
plane more clearly.
For instance, at 1 mile from the Pentagon wall, the plane was xxx feet
and moving xxx knots. Controls, accelerometers, etc. show changes
as the flight progresses.
If the RADAR altitude suddenly shows a change in altitude of 60 feet while
the accelerometers, or Pressure Altitude follows a trend, you can conclude
that the plane was passing over an object.
RADAR altimeters use RF [radio frequency] signals t determine height by
sending out frequency waves and measuring the speed of return once
boucing off an object.
Pressure altimeters use (local) atmospheric pressure to determine height
so flying over objects (buildings, trees, etc.) has no effect on the PA reading.
The reason I ask is that it appears that all the discussions prior to this latest work have revolved around what the NTSB .csv shows as the
last altitude (and other parameters) readings when it would be quite obvious to anyone actually decoding the data that extra readings existed.
It's a valid question. Keep in mind the NTSB data has errors; specifically
in this topic altitude. The CSV altitude and animation altitudes do not
coincide throughout the flight. This is a problem and easily detected by
As it has been corrected and exposed by P4T, we have to ask why these
parameters differ if both files (animation and CSV) are derived from the
same .fdr file.
Some will say the animation is "a working copy". but they don't understand
the the PA at the beginning of the animation is fine, while the PA crossing
through 18,000 feet ASL does not match the CSV changes in the BARO COR column.
You are aware of the 'snap back' that I'm referring to?
Anyway, just remember:
Radar Altimeters are not used for the approach until they are in the
clearway zone approaching a runway on a Cat III ILS autoland. The
pressure altimeter will also correspond during this approach, unlike
at the Pentagon.