Boeing 707 - 767 Comparison

Leslie E. Robertson - Chief Engineer of the World Trade Center

In 1966, Robertson designed the structural elements of the WTC towers to withstand the impact of the largest airliner then in service, the Boeing 707.

The above image is taken from Chapter 1 of the WTC Report [FEMA PDF of report]. To see how willing to "stretch the truth" the authors of the report are, compare the above image to the original (which can be found here). Notice that they have "accidently" quoted the length, height and wingspan of one of the early 707's (possibly the Boeing 707-120) and the weight, fuel capacity and speed of the more common Boeing 707-320B (the aircraft that most people associate with the name, Boeing 707). The above graphic has been edited to give a more accurate picture.

To summarize the aircraft:

The maximum takeoff weight for a Boeing 707-320B is 336,000 pounds.
The maximum takeoff weight for a Boeing 767-200ER is 395,000 pounds.

The wingspan of a Boeing 707 is 146 feet.
The wingspan of a Boeing 767 is 156 feet.

The length of a Boeing 707 is 153 feet.
The length of a Boeing 767 is 159 feet.

The Boeing 707 could carry 23,000 gallons of fuel.
The Boeing 767 could carry 23,980 gallons of fuel.

The cruise speed of a Boeing 707 is 607 mph = 890 ft/s,
The cruise speed of a Boeing 767 is 530 mph = 777 ft/s.

The Boeing 707 and 767 are very similar aircraft, with the main differences being that the 767 is slightly heavier and the 707 is faster.

Since the Boeing 707 had a higher thrust to weight ratio, it would be traveling faster on take-off and on landing.

The thrust to weight ratio for a Boeing 707 is 4 x 18,000/336,000 = 0.214286.

The thrust to weight ratio for a Boeing 767 is 2 x 31,500/395,000 = 0.159494.

In all the likely variations of an accidental impact with the WTC, the Boeing 707 would be traveling faster. In terms of impact damage, this higher speed would more than compensate for the slightly lower weight of the Boeing 707.

In conclusion we can say that if the twin towers were designed to survive the impact of a Boeing 707, then they were necessarily designed to survive the impact of a Boeing 767.


See also: The 9/11 WTC Collapses: An Audio-Video Analysis


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