Occasional researchers have speculated that the radar data and seismic data concerning the impact of AA11 into the World Trade Center, North Tower, do not agree. That erroneous interpretation, in their view, somehow supports the notion that the towers were brought down by deliberate, nefarious means.
None of that speculation is true; it is based on an apples and oranges comparision. The radar data and seismic data are in agreement. In this brief article I will establish the facts of the matter for serious researchers, historians and academicians so that they can put the issue in persepective.
The Seismic Data
Seismic data, as depicted by Popular Mechanics, established an impact time for AA11 of 8:46:26. That data, fully considered, does not support any conspiracy theory, as clarified by seismologists at Columbia University’s Lamont-Doherty Earth Observatory in Palisades, N.Y.
The Commission Report
The 9-11 Commission reported an impact time of 9:46:40, taken from the National Traffic Safety Board (NTSB) report on AA11. The Commission, by convention and for convenience, used NTSB-established times for the ipact of all four hijacked aircraft on 9/11.
Commission analysis was based on the Air Force radar data provided by the 84th Radar Evaluation Squadron (RADES). My analysis then, and now, was that the impact, according to radar, was between one to two radar sweeps earlier than the NTSB-established time, closer to one rather than two. A radar sweep is twelve seconds. Therefore, the assessment was that the actual impact time, according to radar, was between 8:46:16 and 8:46:28, and closer to the latter.
I had no issue with the convention of using NTSB-established times since the time difference was a matter of seconds. I did point out that the difference might come into play when/if the narrative used times rounded to the minute. Even that concern turned out to be inconsequential. The popular narrative, today, is that AA11 impacted at 8:46.
History Commons timeline headings, for example, all round down to 8:46. The timeline cites several sources, including an FAA timeline in which FAA listed that it lost AA 11 at 8:46:31 on radar and that the impact time was 8:46:35.
Of note, Wikipedia currently (Feb 25, 2012) reports a time of 8:46:30, as established by the National Institute of Standards and Technology (NIST), a time consistent with both the radar data and the seismic data.
There is data still to come from the Commission files, including any of my workfiles which I did not print off and archive. Additional primary source information will someday be realeased–the infra-red times for all four impacts as observed by satellite and as recorded as log entries in the CMOC (Cheyenne Mountain Operations Center) log.
So, how did the 8:46:40 time come about?
Radar data for AA11 was depicted graphically by the NTSB in Figure 2 of its February 19, 2002, “Flight Path Study, American Airlines Flight 11,” viewable at this link. It is clear from the graphic and from the NTSB study that a time of 9:46:40 was extrapolated from Figure 2. However, that extrapolated time is for elevation zero and does not account for the height of the impact above that datum. It is also clear from the graphic that an extrapolated radar time for the height of the impact is consistent with seismic data, my analysis of Air Force radar data, the FAA assessment of its radar data, and the NIST established time of 9:36:30.
Comparing Apples and Oranges
It is not valid to compare an extrapolated, published radar time of 8:46:40 with a seismic data time of 8:46:26. It is valid to compare radar data to seismic data. Responsible researchers will do so and will find the times to be consistent.