In another interview, with the BBC recorded 2 months after 9/11, Leslie Robertson had this to say; "And then of course with the 707 to the best of my knowledge the fuel load was not considered in the design, and indeed I don't know how it could have been considered. But, and with the 767 the fuel load was enormous compared to that of the 707, it was a fully fuelled airplane compared to the 707 which was a landing aircraft. Just absolutely no comparison between the two."
Well, based on documentation that the NIST obtained in 2003, the Towers most definitely were designed to handle a 600 mph Boeing 707 impact.
In a followup article for the NY Times, published on December 3, 2003, the same reporter, James Glanz, now, in effect retracted his earlier story;
"The investigators also said that newly disclosed Port Authority documents suggested that the towers were designed to withstand the kind of airplane strike that they suffered on Sept. 11.
Earlier statements by Port Authority officials and outside engineers involved in designing the buildings suggested that the designers considered an accidental crash only by slower aircraft, moving at less than 200 miles per hour.
The newly disclosed documents, from the 1960's, show that the Port Authority considered aircraft moving at 600 m.p.h., slightly faster and therefore more destructive than the ones that did hit the towers, Dr. S. Shyam Sunder, who is leading the investigation for the National Institute of Standards and Technology in the Commerce Department said."
The reference to these documents appears in NCSTAR 1-2, 8.2 AIRCRAFT IMPACT DAMAGE ANALYSIS, 8.2.1 Safety of the WTC Towers in Aircraft Collision
"Finding 11 acknowledges that " The documents indicate that a Boeing 707, the largest commercial aircraft at the time, flying at 600 mph was considered and that the analysis indicated that such collision would result in only local damage which could not cause collapse or substantial damage to the building and would not endanger the lives and safety of occupants not in the immediate area of impact. No documentary evidence of the aircraft impact analysis was available to review the criteria and methods used in the analysis of the aircraft impact into the WTC towers, or to provide details on the ability of the WTC towers to withstand such impacts."
Here are a few of the salient points that the NIST found in the discovered Port Authority documents from February 3, 1964:
1. A structural analysis was carried out by the firm of Worthington, Skilling, Helle & Jackson and is the most complete and detailed of any ever made for any building structure. The preliminary calculations alone cover 1,200 pages and involve over 100 detailed drawings.
2. The buildings have been designed for wind loads of 45 lbs per square foot which is 2.5 times the New York City Building Code requirements of 20 lbs per square foot, the design load for the Empire State, Pan American and Chrysler Buildings. In addition to static wind loads, a complete dynamic analysis has been made to take into account extremely high velocity gusts.
3. The buildings have been investigated and found to be safe in an assumed collision with a large jet airliner (Boeing 707 - DC 8) travelling at 600 miles per hour. Analysis indicates that such collision would result in only local damage which could not cause collapse or substantial damage to the building and would not endanger the lives and safety of of occupants not in the immediate area of impact.
7. The design has been reviewed by some of the most knowledgeable people in the construction industry. In a letter to John Skilling, the Structural Engineer for the World Trade Center, the Chief Engineer of the American Bridge Division of U.S. Steel Corporation said:
"In reviewing this design with our Operating and Construction Departments, we are very optimistic that you have turned a new page in the design of structural steel."
