How fast were the planes going?

[Kevin Fenton]

For the computer modelling on which its report, which you can find here http://wtc.nist.gov/pubs/NISTNCSTAR1Draft.pdf, was based, NIST used speeds of 443 (Case A, base case) and 472 (Case B, severe case) for American 11 and 542 (Case C, base case) and 570 (Case D, severe case) for United 175 (page 107/161). The majority of the text of the report, such as the comparison tables you can find on page 148/202 and page 149/202, uses Cases B (North Tower) and D (South Tower).

How did NIST arrive at these figures of 472 mph and 570 mph? How do they compare with those of other scientists who estimated the plane speed?

NIST’s Estimates
The details of NIST’s plane speed estimates cannot be found in the report itself, but in one of the subsidiary reports, called the Baseline Structural Performance and Aircraft Impact Damage Analysis of the World Trade Center Towers, which you can find here: http://wtc.nist.gov/pubs/NISTNCSTAR1-2Draft.pdf
Chapter 6 deals with the plane speed estimates.

The best way of determining the planes’ speeds is to examine the various videos of their impact, but there is more than one way of doing this.
NIST’s first method is called Complex Motion Analysis (this section begins on page 153/269) and it comes up with speeds of 435 mph for American 11 and 497 mph for United 175.
The second method is called Simplified Motion Analysis (this section begins on page 154/272) and it comes up with speeds of 451 mph for American 11 and 542 mph for United 175.
It seems that Complex Motion Analysis is generally preferred to Simplified Motion Analysis, but NIST preferred the second method because apparently, “… the range of the camera could only be estimated. If the camera was close to the object motion, the range of the camera would have a significant effect on the perceived scale of the objection in motion. Second, the scale of the image was determined from the dimensions of the towers in the field-of-view, which took up a relatively small portion of the field of view… Third, and most important, there were measurable distortions in the camera fields of view.” However, one of the videos made available to MIT (the “Brooklyn Bridge video”), which NIST also appears to have examined, contained neither problems determining the distance from the WTC, nor distortions due to panning and zooming.

MIT Estimate
MIT performed an estimate of the plane speed, which can be found here http://web.mit.edu/civenv/wtc/PDFfiles/Chapter%20III%20Aircraft%20speed.pdf. MIT arrived at the figures of 429 mph for American 11 and 503 mph for United 175. The author was confident of the United 175 estimate, because of the good quality of the Brooklyn Bridge video, but less confident of the American 11 estimate.

FEMA Estimate
In Section 1.3 Timeline and Event Summary, FEMA says that, “According to government sources, the speed of impact into the north tower was estimated to be 410 knots, or 470 miles per hour (mph), and the speed of impact into the south tower was estimated to be 510 knots, or 590 mph.” There are two problems with this (1) 590 mph is not a safe speed for a Boeing and could lead the aircraft to break up, although no such breaking up was visible; (2) What are the “government sources”? The only explanation I can think of is that this must be radar data. If this is the case, they should be reduced by 10% as, according to the MIT author, “The radar speeds are basically 10% larger, a difference that could easily be explained.” Reducing them by 10% gives us speeds of 423 mph for American 11 and 531 mph for United 175.
http://www.fema.gov/library/wtcstudy.shtm

Conclusion
The FEMA estimate seems to be based on radar data and, as such, is unreliable. The MIT and NIST Complex Motion Analysis figures are strikingly similar – 429 mph and 435 for American 11 and 503 mph and 497 mph for United 175. NIST’s reasoning for preferring the Simplified Motion Analysis was incorrect, as the Brooklyn Bridge Video did not have the defects NIST referred to, making this video the best evidence of the speed of United 175.

If we spilt the distance between the two best estimates we get 432 for American 11 and precisely 500 mph for United 175. NIST’s base case numbers are 11 mph (2.5%) more for American 11 and 42 mph (8.5%) more for United 175. NIST’s severe case numbers – the ones they usually use in their report – are 40 mph (9%) more for American 11 and 70 mph (14%) more for United 175. Indeed, the severe case speeds of 472 mph for American 11 and 570 mph for United 175 were not even supported by NIST’s own estimates.

This is indicative of a pattern in the NIST report – they take high-end estimates and then bump them up a bit. I wonder why?

[pox americana]

1. It's called creative accounting

or the Enron way, and it's supposed to last just long enough for the criminals-in-chief to make their nut and skedaddle.

I can't wait to see what the NIST "overlooked" or "factored out" of their bogus calculations when the truth finally comes out, and it will.