Why are you so nasty?
... to your question:
The SCC in the 22. floor was destroyed by the fireball (!), but had a back-up, the Operations Control Center (OCC) in the underground:
"A new operations center (OCC) will contain backup for the security command center (SCC), and the security command center will contain backup for operations center functions, including alarms, intercoms and elevator controls. Remote processors for access control and alarms at the parking garages, and workstations at the guard booths, parking office, visitor centers and security command center and other areas, are connected to a main, redundant file server."
Both Centers were not operable on 9/11.
For the top-down demolition itself, it was not necessary. But it was necessary to hinder the fireman from their work and to cover up the plot.
from
http://z10.invisionfree.com/Loose_Change_Forum/index.php?showtopic=18745
"From other sources we know that the OCC wasn't directly affected from the explosions like the SCC.
Look again at this quote from transcript 37 we already used before:
WTCCH. 09 - POLICE DESK - 3541 CENTER
SEPTEMBER 11,2001
WORLD TRADE CENTER - CH. 09
POLICE DESK - 3541 - CENTER
DURATION: 1.25 HOURS
PAPD OFFICER MAGGETT:
Port Authority Police, Officer Maggett.
ED CALDERONE - OCC:
Maggett, this is Ed at the OCC. I got word that there's an explosion down on B-4. We got people hurt down there, B-4.
PAPD OFFICER MAGGETT:
B-4?
(...)
That the OCC wasn't directly affected is also confirmed by this report of which we can conclude of that the CCTV still functioned in the OCC. Note also this statement from the report:
When the first plane hit, Compas was in his office on the basement level of the hotel. "It sounded to me as if there were three loud bangs and then the building shook," he says.
Interestingly, he experienced three loud bangs and then the building shock. As the building shock due to the plane impact, shouldn't the bangs, travelling with the sound of speed, be heared after the building shock?
Note that Compas left the OCC after the first plane hit, Ed Calderone left also the OCC for helping people, same as Douglas Karpiloff who was last time seen in the OCC, before he went out to help people.
And from William Rodriguez we know, that the OCC wasn't even manned when he was there, before the second plane hit:
I find water all over, run straight to the south tower where they have the OCC (operation control center) that was created after 1993. They spent $155 million to retrofit the building, and to supposedly straighten it out after the 1993 bombing, and to set up a whole security system, the control center. When I got there and started hitting the window there was nobody there. There was nobody there—the control center, where they have all the cameras, and the recordings. (Source)
Indeed, from the 9/11 Commission Hearings we also know that the OCC didn't play an important role in the firefighting and rescue efforts. The NIST "Emergency Response Operations Report" only mentions the OCC twice relating to the emergency response:
* A building Fire Safety Director spoke with one of the FDNY Chiefs about the possibility of using elevator phones for communication with the building's Operation Command Center (OCC). This person and a FDNY Battakion Chief were dispatched to go and check it out. These men were never seen again. (NIST NCSTAR1-8, p.46)
* 8:58:04 WTC Security radio report, PA Channel X- "What elevators are running in Building number One?"...(?)...OCC...(?)... "S2 to all security guards, hold your posts. Don't allow people in...(?).... Do not allow anyone into the courtyard of any ...(?).... leading into the.....(?)...copy?" (NIST NCSTAR1-8, p.200)
According to NIST, the OCC had also access to the electronically controlled doors:
The first door to access the stairwell to the roof was protected by an acess card reader. Upon opening the first door, the individual would enter a vestibule where, upon showing ID to a closed-circuit television monitored at the Operations Control Center (OCC), the door would be electronically unlocked from the OCC. (NIST NCSTAR 1-7, p.41)
So this means that also the OCC was affected by the explosions as it had lost control over the electronically accessible doors.
(It should be noted that the NIST confused the location of the OCC, "The Operation Control Center was located in the B1 Level of WTC 1 and was a backup Fire Command Center." (NIST NCSTAR 1-7, p.39). This would of course suggest that the WTC1 basement explosions did not produce severe damage when the nearby OCC wasn't even affected. The NIST makes this error only in Draft 7, in Draft 8 the location is given correct: "A new Operations Control Center with the capability to monitor all HVAC systems and elevators in both towers was constructed on the B1 level of WTC2" (NIST NCSTAR 1-8 , p.17) )
From this NIST-figure we can conclude that also the control over the HVAC system was lost.
Smoke (dark grey) in almost all floors of the tower indicates that the HVAC system controls were inoperable.
HVAC systems that are not shot down during a fire, or are set in a mode that re-circulates air through the building, may directly cause smoke spread through the building. (NIST NCSTAR1-4 ,p.70)
Of course smoke on almost all floors interferes the emergency efforts in a negative way and slows down the firefighting attempts.