The physics of 9/11

Michelle Malkin re-visits the 9/11 Conspiracy Theory. Dismissing a Brigham Young professor as a "Moonbat," MM suggests the prof might be ready to sign on with Oliver Stone. The prof says he thinks the Twin Towers were destroyed by explosives, more so than by jet planes.

I read all the posts, and I got thinking about some of the conspiracy-theory webpages that were up around 2002 and 2003. I didn't print them off or save the URLs, but I do vividly recall one of the sites talking about the cell phone calls that were said to have been made from the doomed jetliners and how such calls from private cell phones would have set off a "cascading" effect.

I did a little digging and found the following on a cache of an old message board:
If the hijackings of September 11 were staged, the organization responsible would also be sure to add other elements to the basic plan, not only developing lists of hijackers, but sending fake cellphone calls from some of the passengers. The following analysis focuses on Flight 93, from which more alleged cellphone calls were made than from the other three flights combined. It could be called the "Cellphone Flight." Like the staged attacks themselves, the calling operation would be complex, involving the a) deployment of voice mimicry techniques, gathering personal intelligence on at least some of the passengers, c) coordination of calls with the operation's timeline.

Any analysis of the cellphone and "airfone" calls from Flight 93 must begin with some basic, high-altitude cellphone facts. According to AT&T spokesperson Alexa Graf, cellphones are not designed for calls from the high altitudes at which most airliners normally operate. It was, in her opinion, a "fluke" that so many calls reached their destinations. (Harter 2001) In the opinion of a colleague of mine who has worked in the cellphone industry, it was a "miracle" that any of the calls got through from altitude. (See the recent proposal to install equipment to make cellphone calls possible from aircraft.) An aircraft, having a metal skin and fuselage, acts like a Faraday cage, tending to block or attenuate electromagnetic radiation. One can make a cellphone call from inside an aircraft while on the ground because the weakened signal is still close enough to the nearest cellsite (relay tower) to get picked up. Once above 10,000 feet, however, calls rarely get through, if ever.

Here is the statement of an experienced airline pilot: "The idea of being able to use a cellphone while flying is completely impractical. Once through about 10,000 feet, the thing is useless, since you are too high and moving too fast (and thus changing cells too rapidly) for the phone to provide a signal." (AVWeb, 1999)

People boarding aircraft for the last decade or so have all heard the warnings to turn off their cellphones for the duration of the flight. The reasons for this regulation are somewhat mysterious, since the usual explanation, that delicate aircraft electronics might be affected by cellphone signals, is cast somewhat in doubt by the fact that all avionics are shielded from stray electromagnetic radiation. (Spitzer 1987) On the other hand, the FCC had apparently requested that airlines make this rule, owing to the tendency for cell phone calls made from aircraft at lower altitudes to create "cascades" that may lead to breakdown of cellsite operations. (Fraizer 2002)

The cascade problem is more likely at altitudes of 10,000 feet or lower, where reaching a cellsite, although still a touch-and-go matter, is more easily accomplished. However, because of its superior position, the cellphone may reach several cellsites at once. This can create problems, as software that determines which site is to handle the call makes its judgment based on the relative strength of calls. If the call is made from an overhead position, it may well not be able to distinguish relative strength at different cellsites. When this happens it is designed to close off the calling channel, selecting another channel in its place. But the same problem of deciding which cellsite should handle the call also occurs on the new channel, so the new channel is closed, and so on. One by one, in a rapid cascade that would last only seconds, all the channels would be closed, leading to a network-wide breakdown.

As I have pointed out elsewhere, cellphone calls from commercial aircraft much over 8000 feet are essentially impossible, while those below 8000 feet are highly unlikely down to about 2000, where they become merely unlikely. (Dewdney 2003) Moreover, even at the latter altitude (and below), the handoff problem appears. Any airliner at or below this altitude, flying at the normal speed of approximately 500 mph, would encounter the handoff problem (Dewdney 2003). An aircraft traveling at this speed would not be over the cellsite long enough to complete the electronic "handshake" (which takes several seconds to complete) before arriving over the next cellsite, when the call has to be handed off from the first cellsite to the next one. This also takes a few seconds, the result being, in the optimal case, a series of broken transmissions that must end, sooner or later, in failure.

It must also be remarked that the alleged hijackers of the Cellphone Flight were remarkably lenient with their passengers, allowing some 13 calls. However, it would seem highly unlikely that hijackers would allow any phone calls for the simple reason that passengers could relay valuable positional and other information useful to authorities on the ground, thus putting the whole mission in jeopardy.
One thing's for sure... we need closure on the 9/11 issue.

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