January 23, 2003: Engineers Release Report on Pentagon Crash

Sixteen months after the attack occurred, the American Society of Civil Engineers (ASCE) releases its Pentagon Building Performance Report on the Pentagon’s architectural response to the impact, blast, and subsequent fires caused by the Flight 77 crash on 9/11. [American Society of Civil Engineers, 1/17/2003] The report, which was finished several months earlier (see September 14, 2001-April 2002), admits “the volume of information concerning the aircraft crash… is rather limited,” but the team is able to give some details of the impact. The report reproduces the five frames of security camera footage made public in 2002 that showed the strike on the Pentagon (see March 7, 2002), seeing in them the approaching aircraft with its top about 20 feet above ground before exploding against and into the building. [Mlakar et al., 1/2003, pp. 14 ] The report notes the plane struck a construction generator and vent structure on the lawn and speculates “portions of the wings might have been separated from the fuselage before the aircraft struck the building.” [Mlakar et al., 1/2003, pp. 35-36 ] The ASCE finds that the plane hit the northern edge of Wedge One of the building—its southwest corner—which had been recently renovated, and that the plane made a 90 foot hole in the outer wall, destroying most ground floor support columns there and the limestone and brick façade between and in front of them. Aircraft debris is then reported to have passed through the building’s three outer rings E, D, and C, following the plane’s trajectory, entering the unrenovated Wedge Two towards the end of the path of destruction. [Mlakar et al., 1/2003, pp. 39 ] The report does not say what caused the much-debated hole in the wall of Ring C, which led on to an internal driveway in the middle of the building. However, in a section on the damage caused by the debris it notes, “There was a hole in the east wall of Ring C, emerging into AE drive,” and a photo of the C Ring hole is included in the report. [Mlakar et al., 1/2003, pp. 28 ]