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Context of '(8:57 a.m.) September 11, 2001: Fire Chiefs Advise Evacuation of WTC’s South Tower'

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George Tabeek, a security manager with the Port Authority of New York and New Jersey, decides to have an announcement made in the South Tower of the World Trade Center, instructing workers to stay in, or return to, their offices, instead of evacuating. [New Jersey Star-Ledger, 9/6/2011; ABC News, 9/10/2011] After Flight 11 hits the North Tower at 8:46 a.m. (see 8:46 a.m. September 11, 2001), many people in the South Tower, who are unclear about what has happened, decide to leave their building. [9/11 Commission, 7/24/2004, pp. 287]
Security Manager Passes on Decision to Fire Command Desk - However, around the same time, Tabeek, the Port Authority’s security manager for the WTC, decides not to evacuate the South Tower and to issue instructions advising workers to go back to their offices. [ABC News, 9/10/2011] Tabeek will later recall that he contacts his “fire safety command” and tells the person he talks with “to evacuate the North Tower, but keep people inside the South Tower.” [New Jersey Star-Ledger, 9/6/2011] Presumably Tabeek means that he contacts the fire command desk in the lobby of the South Tower, which is currently manned by Philip Hayes, a deputy fire safety director. A button at the desk allows fire safety directors to deliver announcements over the tower’s public address system. [Dwyer and Flynn, 2005, pp. 26]
Security Manager's Instruction Leads to Announcement - Shortly after Tabeek gives his instruction to the fire command desk, an announcement, later believed to have been made by Hayes, will go out over the public address system, telling workers in the South Tower that their building is safe and advising them to stay in, or return to, their offices (see (8:50 a.m.) September 11, 2001). [9/11 Commission, 7/24/2004, pp. 287-288; Dwyer and Flynn, 2005, pp. 72] That announcement “may have led to the deaths of hundreds of people,” USA Today will suggest. [USA Today, 9/2/2002] Some security officials in the South Tower will instruct workers, in person, to return upstairs, rather than evacuate (see (8:47 a.m.-9:02 a.m.) September 11, 2001). It is unclear if those officials are, like Hayes, acting on instructions issued by Tabeek. [Observer, 9/16/2001; 9/11 Commission, 7/24/2004, pp. 289]
Instruction Is Inconsistent with Protocol - Tabeek’s instruction reportedly goes against protocol. The 9/11 Commission Report will state: “When a notable event occurred [at the WTC], it was standard procedure for the on-duty deputy fire safety director to make an ‘advisory’ announcement to tenants who were affected by or might be aware of the incident, in order to acknowledge the incident and to direct tenants to stand by for further instructions. The purpose of advisory announcements, as opposed to ‘emergency’ announcements (such as to evacuate), was to reduce panic.” Therefore, according to the 9/11 Commission Report, “A statement from the deputy fire safety director informing tenants that the incident had occurred in the other building” would be “consistent with protocol.” However, “the expanded advice” that Tabeek asks to be given—for workers to stay in, or return to, their offices—“did not correspond to any existing written protocol.” [9/11 Commission, 7/24/2004, pp. 288, 544]
Security Manager Thinks Evacuation Would Put Workers in Danger - Tabeek will explain why he decided to instruct workers to stay in the South Tower, telling ABC News he was “worried about the debris raining down from the crippled North Tower onto the plaza below,” and he was therefore “afraid that if he evacuated people who he thought were safe in the South Tower… they’d be in grave danger from the falling debris.” He will tell the New Jersey Star-Ledger, “If these people’s lives in [the South Tower] are not in danger, if I put them outside, their life is in danger.” Tabeek will also explain his decision by saying, “We never took into consideration a dual attack.” In response to criticism of his decision, he will say, “I can’t go back on the orders I gave, because at the time it was the right thing to do.” [New Jersey Star-Ledger, 9/6/2011; ABC News, 9/10/2011]

Entity Tags: George Tabeek, Philip T. Hayes

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Alan DeVona.Alan DeVona. [Source: Atlas Shrugs]An officer with the Port Authority Police Department (PAPD) calls for the evacuation of the upper floors of the North Tower of the World Trade Center over a PAPD radio channel. Transcripts of PAPD radio transmissions will show that at 8:49 a.m., three minutes after Flight 11 crashed into the North Tower (see 8:46 a.m. September 11, 2001), the PAPD officer talks to the PAPD desk, which is in Building 5 of the WTC, just northeast of the North Tower. He says: “Start doing the evac, the upper levels. Have the units put on the Scott air packs.” The officer at the PAPD desk then radios all PAPD units and tells them to “bring Scott air packs [to] One World Trade,” i.e. the North Tower. [Port Authority of New York and New Jersey, 9/11/2001, pp. 2 pdf file; Port Authority of New York and New Jersey, 11/12/2001, pp. 16 pdf file; National Institute of Standards and Technology, 9/2005, pp. 195]
Patrol Sergeant Recalls Requesting Evacuation - It is unclear which PAPD officer requests the evacuation at this time. According to some accounts, Alan DeVona, the PAPD patrol sergeant at the WTC, makes the request. [Port Authority of New York and New Jersey, 11/12/2001, pp. 16 pdf file; Dwyer and Flynn, 2005, pp. 78] DeVona will later recall that he had just walked out from the PAPD desk in WTC 5 when he heard the explosion as Flight 11 hit the North Tower. Along with his colleague, Anthony Basic, he radioed the PAPD desk and reported that the top floors of the North Tower were on fire, due to a “possible aircraft collision.” He headed into the North Tower to coordinate with emergency agencies as they arrived there. DeVona will recall that he then “radios to have all WTC police units get Scott air packs and begin evacuation of [the North Tower].” He will subsequently be “approached by numerous PAPD units as they entered the lobby” of the North Tower, and he “dispatches them through the concourse to evacuate the complex.” [Devona, 3/28/2002, pp. 24 pdf file]
Police Commander Recalls Requesting Evacuation - However, Captain Anthony Whitaker, the PAPD commanding officer at the WTC, will also say that he calls for the evacuation of the WTC around this time. Whitaker was on duty in the shopping mall beneath the Twin Towers when Flight 11 hit the North Tower. [Dwyer and Flynn, 2005, pp. 78] He heard a “strange roar” and saw a “gigantic fireball” coming out of the lobby of the North Tower. He then contacts the PAPD desk in WTC 5. Whitaker will recall, “I had no idea what had just happened, but I knew it was bad.” Therefore, he will say, “I ordered the cop at the desk to begin a full-scale evacuation of the entire complex.” This will mean the evacuation of “both towers and the adjoining buildings.” Whitaker contacts one of his sergeants and then, he will recall, “we started placing Port Authority cops in strategic locations in the shopping mall to direct the evacuation.” Whitaker will say that after 9/11, he is repeatedly asked, “Why did you give that order to evacuate at that particular time?” following the first crash, but before the second plane hit the WTC. His explanation will be: “It just occurred to me that whatever was going on—and I still didn’t know what that was—was beyond my ability as a commanding officer of that facility to do anything about it. So it seemed to me that the only prudent thing to do was start a full-scale evacuation and get everybody out of there.” [Fink and Mathias, 2002, pp. 23-24; Murphy, 2002, pp. 179-181]
Evacuation Orders Cannot Be Heard by Fire Safety Directors - At 9:00 a.m., Whitaker will call for an evacuation of the entire WTC complex (see 8:59 a.m.-9:02 a.m. September 11, 2001). However, both that instruction and the current one are given over PAPD radio channel W, which cannot be heard by the deputy fire safety directors in the Twin Towers, who are able to make announcements to the buildings’ occupants over the public address systems. [WTC News, 8/1995 pdf file; Port Authority of New York and New Jersey, 11/12/2001, pp. 19 pdf file; 9/11 Commission, 7/24/2004, pp. 293; National Institute of Standards and Technology, 9/2005, pp. 195, 201] An announcement advising workers to evacuate will only go out over the public address system in the South Tower at 9:02 a.m. (see 9:02 a.m. September 11, 2001). And attempts to order workers to evacuate the North Tower are unsuccessful because that building’s public address system was damaged by the plane crash (see (Between 8:47 a.m. and 8:55 a.m.) September 11, 2001). [New York Times, 5/18/2004]
PAPD Investigates All Reports of Fires at WTC - The WTC is a Port Authority property, which means it is patrolled by the PAPD—the Port Authority’s independent police agency. Members of the PAPD respond to “thefts, injuries, fires, all species of crisis large and small, almost always more quickly than the city emergency responders could get there,” according to New York Times reporters Jim Dwyer and Kevin Flynn. “By plan,” Dwyer and Flynn will write, “the PAPD checked out every report of fire” and “its officers were trained in at least rudimentary firefighting.” [Dwyer and Flynn, 2005, pp. 78]

Entity Tags: Anthony Basic, Anthony Whitaker, Alan DeVona, Port Authority Police Department

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

An announcement goes out over the public address system in the South Tower of the World Trade Center, telling workers that an incident has occurred in the other WTC tower and their building is safe, and advising them to stay in—or return to—their offices, rather than evacuate. [USA Today, 9/2/2002; 9/11 Commission, 7/24/2004, pp. 287-288] After Flight 11 hit the North Tower at 8:46 a.m. (see 8:46 a.m. September 11, 2001), many people in the South Tower were unaware of what had happened. “Some believed an incident had occurred in their building; others were aware that a major explosion had occurred on the upper floors of the North Tower,” the 9/11 Commission Report will state. As a result, many workers decided to leave the South Tower. [9/11 Commission, 7/24/2004, pp. 287] As they do so, an announcement is made over the public address system.
Announcement Says South Tower Is Secure - Brian Clark, an executive with Euro Brokers who also serves as a fire warden and is on the 84th floor of the South Tower, will later describe this announcement. “First, the strobe lights flashed, as they did during their normal fire drills,” he will say. “The alarm system gave a little bit of a whoop, whoop… to alert you to an announcement about to be made. Then the very familiar voice, the one we heard all the time, came over the system.” Clark will recall that the voice says: “Your attention, please, ladies and gentlemen. Building 2 [i.e. the South Tower] is secure. There is no need to evacuate Building 2. If you are in the midst of evacuation, you may use the re-entry doors and the elevators to return to your office. Repeat, Building 2 is secure.” [PBS, 4/30/2002; Dwyer and Flynn, 2005, pp. 72] The announcement is made two or possibly three times, according to USA Today. [USA Today, 9/2/2002] Florence Engoran, a credit analyst working in the South Tower, will recall it being made “[o]ver and over and over again.” [DiMarco, 2007, pp. 50]
Announcement May Lead to Hundreds of Deaths - Many people in the South Tower remain on their floors after hearing the announcement, while others who were leaving the building turn around and head back upstairs. [9/11 Commission, 7/24/2004, pp. 289] USA Today will suggest that the announcement therefore “may have led to the deaths of hundreds of people.” [USA Today, 9/2/2002] According to the National Institute of Standards and Technology, of those who die in the South Tower, only 11 are below where the plane hits the tower at 9:03 a.m. (see 9:03 a.m. September 11, 2001), and 619 are in or above the point of impact. [National Institute of Standards and Technology, 9/2005, pp. 44]
Announcement Goes against Protocol - The announcement is later believed to have been made by Philip Hayes, a deputy fire safety director at the WTC, who is manning the fire command desk in the lobby of the South Tower. Fire safety directors are trained to read scripted announcements from a loose-leaf binder. But, according to the 9/11 Commission Report, the advice given in the announcement, for people to stay in, or return to, their offices, “did not correspond to any existing written protocol.”
Security Manager Decided to Instruct Workers Not to Evacuate - The 9/11 Commission Report will also state, “We do not know the reason for the announcement, as both [Hayes] and the director of fire safety for the WTC complex perished in the South Tower’s collapse.” [USA Today, 9/2/2002; 9/11 Commission, 7/24/2004, pp. 288; Dwyer and Flynn, 2005, pp. 26, 72] However, George Tabeek, a security manager with the Port Authority of New York and New Jersey, will admit having made the decision to instruct South Tower workers to return to their offices (see Shortly After 8:46 a.m. September 11, 2001). [ABC News, 9/10/2011] Some security officials in the South Tower instruct workers, in person, to return upstairs, rather than evacuate (see (8:47 a.m.-9:02 a.m.) September 11, 2001). But finally, about a minute before Flight 175 hits the South Tower, an instruction will be broadcast over the public address system informing workers that they can begin an evacuation if conditions warrant it (see 9:02 a.m. September 11, 2001). [Observer, 9/16/2001; 9/11 Commission, 7/24/2004, pp. 289]

Entity Tags: Philip T. Hayes, Brian Clark, Florence Engoran

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Fire department commanders in the lobby of the North Tower of the World Trade Center instruct an officer with the Port Authority Police Department and building personnel in the North Tower to evacuate the South Tower of the WTC. They do this not because of concern about a plane hitting the South Tower, but because, in their judgment, “the impact of the plane into the North Tower made the entire complex unsafe,” according to the 9/11 Commission Report. The exact time at which the fire chiefs give the instruction is unclear; the 9/11 Commission Report will only state that they have given it “by approximately 8:57.” However, according to the 9/11 Commission, “there is no evidence that this advice was communicated effectively to the building personnel in the South Tower.” [9/11 Commission, 4/19/2004 pdf file; 9/11 Commission, 7/24/2004, pp. 287, 290] All the same, at 9:02 a.m., an announcement will be made over the public address system in the South Tower, telling workers that they can begin an orderly evacuation of the building if conditions warrant it (see 9:02 a.m. September 11, 2001). [9/11 Commission, 7/24/2004, pp. 289]

Entity Tags: Port Authority Police Department, New York City Fire Department

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Anthony Whitaker.Anthony Whitaker. [Source: ABC News]Sergeant Alan DeVona, an officer with the Port Authority Police Department (PAPD), calls for the evacuation of the Twin Towers over a PAPD radio channel, and his colleague, Captain Anthony Whitaker, then calls for the evacuation of the entire World Trade Center complex, but their orders are apparently not passed on [Port Authority of New York and New Jersey, 11/12/2001, pp. 19 pdf file; 9/11 Commission, 5/18/2004 pdf file; Dwyer and Flynn, 2005, pp. 78-79; National Institute of Standards and Technology, 9/2005, pp. 200-202] DeVona, the PAPD patrol sergeant at the WTC, is currently in the lobby of the North Tower, coordinating with emergency agencies as they arrive there. [Devona, 3/28/2002, pp. 24 pdf file] Whitaker, the PAPD commanding officer at the WTC, is outside the Twin Towers, looking up at the burning North Tower. [Fink and Mathias, 2002, pp. 25; Murphy, 2002, pp. 184]
Officers Request Evacuation of the WTC - At 8:59 a.m., DeVona calls for the evacuation of the Twin Towers. “As soon as we’re able,” he says over the PAPD radio channel, “I want to start a building evacuation, Building 1 [i.e. the North Tower] and Building 2 [i.e. the South Tower], till we find out what caused this.” Immediately after DeVona says this, at 9:00 a.m., Whitaker makes a similar request over the same radio channel. “Let’s begin an evacuation of the entire complex,” he says. “All buildings, copy?” [Port Authority of New York and New Jersey, 11/12/2001, pp. 19 pdf file; National Institute of Standards and Technology, 9/2005, pp. 200-201] Unlike DeVona, Whitaker is ordering the evacuation of not just the Twin Towers, “but also the five other buildings throughout the 16-acre complex—the mercantile exchange, offices of major investment banking concerns, and government agencies, including the FBI, the Secret Service, and the CIA,” according to New York Times reporters Jim Dwyer and Kevin Flynn. [Dwyer and Flynn, 2005, pp. 79] Whitaker has decided to evacuate the WTC complex “because of the danger posed by highly flammable jet fuel from Flight 11,” which crashed into the North Tower at 8:46 a.m. (see 8:46 a.m. September 11, 2001), and “because of the magnitude of the calamity in the North Tower,” according to the 9/11 Commission. [9/11 Commission, 5/18/2004 pdf file; 9/11 Commission, 7/24/2004, pp. 293]
Request Is the Second Time Evacuation Is Called For - Whitaker will later say that his current request is the “second time” he has called for the evacuation of the WTC complex. He will recall making his previous request—for “a full-scale evacuation of the entire complex”—shortly after Flight 11 crashed. [Fink and Mathias, 2002, pp. 23-25; Murphy, 2002, pp. 180-181, 184-185] Transcripts of PAPD radio transmissions will show that an evacuation was requested at 8:49 a.m., but only for the upper floors of the North Tower (see 8:49 a.m. September 11, 2001). [Port Authority of New York and New Jersey, 9/11/2001 pdf file; National Institute of Standards and Technology, 9/2005, pp. 195] And according to some accounts, that request was made by DeVona, not Whitaker. [Port Authority of New York and New Jersey, 11/12/2001, pp. 16 pdf file; Devona, 3/28/2002, pp. 24 pdf file; Dwyer and Flynn, 2005, pp. 78]
Officer Repeats Order, for the Written Record - At 9:01 a.m., an officer at the PAPD desk in Building 5 of the WTC asks if they should evacuate their building. DeVona instructs the officer to wait, saying, “Stand by on Building 5.” Whitaker then asks the officer at the PAPD desk if they have started a “chrono log” yet. [Port Authority of New York and New Jersey, 11/12/2001, pp. 19 pdf file; National Institute of Standards and Technology, 9/2005, pp. 201] A “chrono” is a written record of what the PAPD is doing. [Murphy, 2002, pp. 182] The officer replies, “That’s affirmative.” At 9:02 a.m., Whitaker repeats his previous instruction, apparently to make sure it is officially recorded. He says: “For the chrono, evacuate all buildings in the complex. You copy? All building in the complex.” The officer at the PAPD desk acknowledges the instruction and then radios all PAPD units in the field, and tells them to evacuate “all tenants in the buildings… at the Trade Center.” [Port Authority of New York and New Jersey, 9/11/2001 pdf file; Port Authority of New York and New Jersey, 11/12/2001, pp. 19 pdf file; National Institute of Standards and Technology, 9/2005, pp. 202]
Orders Not Passed on to Other Agencies - It is unclear whether DeVona and Whitaker’s orders to evacuate the WTC are passed on. Their orders are given over PAPD radio channel W, which cannot be heard by the deputy fire safety directors in the Twin Towers, who are able to make announcements over the buildings’ public address systems. [WTC News, 8/1995 pdf file; 9/11 Commission, 7/24/2004, pp. 293; National Institute of Standards and Technology, 9/2005, pp. 200-202] According to the 9/11 Commission, there is “no evidence” that the orders are “communicated to officers in other Port Authority Police commands or to members of other responding agencies.” [9/11 Commission, 5/18/2004 pdf file] Despite this, an announcement is made over the public address system in the South Tower, advising workers to evacuate, at 9:02 a.m. (see 9:02 a.m. September 11, 2001). Attempts to order workers to evacuate the North Tower are unsuccessful because that building’s public address system was damaged by the plane crash (see (Between 8:47 a.m. and 8:55 a.m.) September 11, 2001). [New York Times, 5/18/2004]

Entity Tags: Alan DeVona, Anthony Whitaker, Port Authority Police Department

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

An announcement is made over the public address system in the South Tower of the World Trade Center, advising workers that they can begin an orderly evacuation of the building if conditions warrant it. [New York Times, 5/17/2004; 9/11 Commission, 7/24/2004, pp. 289] A previous announcement over the public address system instructed people in the South Tower to stay in, or return to, their offices, rather than evacuate (see (8:50 a.m.) September 11, 2001). [9/11 Commission, 7/24/2004, pp. 287-288; Dwyer and Flynn, 2005, pp. 72] The new announcement begins: “May I have your attention, please. Repeating this message: the situation occurred in Building 1 [i.e. the North Tower].” The announcer then says, “If the conditions warrant on your floor, you may wish to start an orderly evacuation.” [New York Times, 5/17/2004] The announcement is presumably made by Philip Hayes, the deputy fire safety director on duty at the fire command desk in the lobby of the South Tower. A button at the desk enables fire safety directors to deliver announcements over the public address system. [Dwyer and Flynn, 2005, pp. 26]
Identity of Person Who Ordered Evacuation Unclear - The new advice, for tenants to evacuate, does “not correspond to any prewritten emergency instruction,” according to the 9/11 Commission Report. [9/11 Commission, 7/24/2004, pp. 289] It is unclear who told Hayes to make the announcement giving this advice. George Tabeek, the Port Authority’s security manager for the WTC, contacted the fire command desks in the Twin Towers immediately after Flight 11 hit the North Tower, with instructions about what to do. His orders for Hayes, however, were to “keep people inside the South Tower” (see Shortly After 8:46 a.m. September 11, 2001). [New Jersey Star-Ledger, 9/6/2011]
Police Commander Called for Evacuation of WTC - Captain Anthony Whitaker, the Port Authority Police Department (PAPD) commanding officer at the WTC, called for the evacuation of the WTC at 9:00 a.m. (see 8:59 a.m.-9:02 a.m. September 11, 2001). However, his instruction was given over PAPD radio channel W, “which could not be heard by the deputy fire safety director in the South Tower,” according to the 9/11 Commission Report. [Murphy, 2002, pp. 184-185; 9/11 Commission, 7/24/2004, pp. 293; National Institute of Standards and Technology, 9/2005, pp. 201] Furthermore, according to the Port Authority, deputy fire safety directors do not generally take direct orders from the PAPD under the regular chain of command. Therefore, the 9/11 Commission Report will state, it is “not known if [Hayes] received the order by the PAPD to evacuate the complex.” [9/11 Commission, 7/24/2004, pp. 544]
Fire Department Responsible for Ordering Evacuations - According to New York Times reporters Jim Dwyer and Kevin Flynn, “The authority to order an evacuation during a fire normally rests with the fire department.” [Dwyer and Flynn, 2005, pp. 79] In a phone call with his counterpart in the North Tower, at 8:49 a.m., Hayes in fact said he would wait to hear from “the boss from the fire department or somebody” before ordering an evacuation of the South Tower (see 8:49 a.m. September 11, 2001). [Port Authority of New York and New Jersey, 9/11/2001 pdf file; 9/11 Commission, 7/24/2004, pp. 287; Dwyer and Flynn, 2005, pp. 27] But whether someone from the fire department told Hayes to order an evacuation is unknown. It is also unclear how long announcements, advising an evacuation, continue for. Hayes and his counterpart in the North Tower are “making announcements that the situation was serious and that occupants should evacuate immediately” for “[a]s long as the [fire alarm system] was still operational,” according to Fire Engineering magazine. [Fire Engineering, 11/1/2002] However, the 9/11 Commission Report will state, “Evidence suggests that the public address system [in the South Tower] did not continue to function after the building was hit.” This would mean no announcements go out after 9:03 a.m., when Flight 175 hits the tower (see 9:03 a.m. September 11, 2001). [9/11 Commission, 7/24/2004, pp. 295] By the time the South Tower collapses (see 9:59 a.m. September 11, 2001), out of around 8,540 people who were originally in the building, 7,940 (93 percent) have made it out and will survive, according to the National Institute of Standards and Technology. [National Institute of Standards and Technology, 9/2005]

Entity Tags: Philip T. Hayes

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Flight 175 hits the WTC South Tower. The picture was taken from a traffic helicopter.Flight 175 hits the WTC South Tower. The picture was taken from a traffic helicopter. [Source: WABC 7/ Salient Stills]Flight 175 hits the South Tower of the World Trade Center (Tower Two). Seismic records pinpoint the time at six seconds before 9:03 a.m. (rounded to 9:03 a.m.). Hijackers Marwan Alshehhi, Fayez Ahmed Banihammad, Mohand Alshehri, Hamza Alghamdi, and Ahmed Alghamdi presumably are killed instantly, and many more in the tower will die over the next few hours. [New York Times, 9/12/2001; CNN, 9/12/2001; CNN, 9/17/2001; North American Aerospace Defense Command, 9/18/2001; USA Today, 12/20/2001; Federal Emergency Management Agency, 5/1/2002, pp. 1-10; New York Times, 5/26/2002; Associated Press, 8/21/2002; USA Today, 9/2/2002] According to the NIST report, the crash time is 9:02:59. [National Institute of Standards and Technology, 9/2005, pp. 38] According to the 9/11 Commission Report, the crash time is 9:03:11. [9/11 Commission, 7/24/2004, pp. 8] Millions watch the crash live on television. The plane strikes the 77th through 85th floors in the 110-story building. Approximately 100 people are killed or injured in the initial impact; 600 people in the tower eventually die. The death toll is far lower than in the North Tower because about two-thirds of the South Tower’s occupants have evacuated the building in the 17 minutes since the first tower was struck. [USA Today, 12/20/2001; National Institute of Standards and Technology, 9/2005, pp. 5-9, 41] The combined death toll from the two towers is estimated at 2,819, not including the hijackers. [Associated Press, 8/21/2002] The impact severs some columns on the south side of the South Tower. Each of the Twin Towers is designed as a “tube-in-tube” structure and the steel columns which support its weight are arranged around the perimeter and in the core. The plane, which is traveling at an estimated speed of around 500 mph (see October 2002-October 2005), severs 33 of the building’s 236 perimeter columns and damages another one. [National Institute of Standards and Technology, 9/2005, pp. 39] The perimeter columns bear about half of the tower’s weight, so the damage to them reduces the tower’s ability to bear gravity loads by about 7.1 percent. [National Institute of Standards and Technology, 9/2005, pp. 6] The actual damage to the 47 core columns is not known, as there are no photographs or videos of it, but there will be much speculation about this after 9/11. It will be suggested that some parts of the aircraft may be able to damage the core even after crashing through the exterior wall (see 8:46 a.m. September 11, 2001). [National Institute of Standards and Technology, 9/2005, pp. 107] According to NIST’s base case model, five of the core columns are severed and another five suffer some damage. [National Institute of Standards & Technology, 9/2005, pp. 235 pdf file] This may reduce the tower’s ability to bear loads by a further approximately 8 percent, meaning that the aircraft impact accounted for a loss of about 15 percent of the building’s strength. This damage will be cited as an event contributing to the building’s collapse after 9/11 (see October 23, 2002 and October 19, 2004). NIST’s base case estimate of damage to the North Tower’s core will be similar, even though the aircraft impact there was dissimilar (see 8:46 a.m. September 11, 2001). Flight 11 hit the North Tower’s core head on, whereas Flight 175 only hits the corner of the South Tower’s core. [National Institute of Standards and Technology, 9/2005, pp. 20-23, 38-41] In addition, some of the fireproofing on the steel columns and trusses may be dislodged (see 8:46 a.m. September 11, 2001). [National Institute of Standards & Technology, 9/2005, pp. xxxvi, 83 pdf file] Photographs and videos of the towers will not show the state of fireproofing inside the buildings, but the National Institute of Standards and Technology (NIST) will try to estimate the damage to fireproofing using a series of computer models. Its severe case model (see (October 2002-October 2005)) will predict that 39 of the 47 core columns are stripped of their fireproofing on one or more floors and that fireproofing is stripped from trusses covering 80,000 ft2 of floor area, the equivalent of about two floors. NIST will say that the loss of fireproofing is a major cause of the collapse (see April 5, 2005), but only performs 15 tests on fireproofing samples (see October 26, 2005). [National Institute of Standards and Technology, 9/2005, pp. 41] According to NIST, less fireproofing is stripped from the North Tower (see 8:46 a.m. September 11, 2001).

Entity Tags: World Trade Center, Marwan Alshehhi, Fayez Ahmed Banihammad, Hamza Alghamdi, National Institute of Standards and Technology, Ahmed Alghamdi, Mohand Alshehri

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

The South Tower of the World Trade Center collapses.The South Tower of the World Trade Center collapses. [Source: Associated Press]The South Tower of the World Trade Center tilts to the southeast and then collapses. It was hit by Flight 175 at 9:03 a.m., 56 minutes earlier (see 9:03 a.m. September 11, 2001). [Washington Post, 9/12/2001; New York Times, 9/12/2001; MSNBC, 9/22/2001; USA Today, 12/20/2001; Associated Press, 8/21/2002; ABC News, 9/11/2002; National Institute of Standards and Technology, 9/2005, pp. 44] The first sign of the collapse is visible on floor 82. [National Institute of Standards and Technology, 9/2005, pp. 87] The angle of the tilt will be disputed after 9/11 (see September-November 2005), as will the time it takes the towers to fall to the ground (see September 12, 2001-September 2005). [Scientific American, 10/9/2001; Eagar and Musso, 12/2001; PBS Nova, 5/2002; National Institute of Standards and Technology, 8/30/2006]

Entity Tags: World Trade Center

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

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