In our local school system, administrators are creating rules to prevent students from having cell phones at all. Rather than focus on the reasonable argument that cell phones are disruptive in class, they instead focus on the “fact” that cell phones could inadvertently set off a bomb, just by being turned on. Is this true? In all of the bombing information I’ve read, terrorists intentionally call a cell phone attached to the bomb or use the alarm clock feature in a cell phone to set off the bomb.
This seems similar to the assertion that cell phones disrupt airplane controls and cause planes to crash. I know of no report that this has ever happened. I also believe that dozens of flights occur daily where cell phones have been accidentally left on, and those planes haven’t dropped out of the sky.
The idea that a cellphone could inadvertently set off a bomb is far-fetched, to say the least. Not impossible, but it’s a stretch. Cell phones are banned on planes ostensibly because they can interfere with navigation and communications equipment, not that they well cause the plane to drop out of the sky. Such interference is also questionable, but better safe than sorry.
There are numerous documented incidents which, while not conclusive, are very telling. There have also been studies which suggest a very real, if small, risk.
They actually tested this on Mythbusters with a plane safely on the ground. Basically, they couldn’t disrupt any of the avionics, even when they had the phones routed through a high powered transmitter. The real answer seems to be that it can screw up things with the towers on the ground, not knowing exactly where to hand the call off to, etc. (cellphones have a range of about 2.5 miles, BTW). Also, the FAA and FCC have done surveys and most passengers don’t like the idea of people being allowed to talk on cellphones while in the air.
Yeah, but when it comes to figuring out a way to cause death, destruction and mayhem, they seem to be pretty good at it. Witness the cement mixer episode.
I’ve got to jump in here and mention that you could set off a bomb w/ a phone if you wired it specifically to do that. It’s not the frequency or transmission that does it, though. It’s the receiver that’s in the bomb that’ll close a circuit.
Before anyone mentions Iraq’s IEDs as support for the idea, that never happens. They use long range cordless telephones calling their base stations, not a phone-to-phone cellular connection.
As a general rule, radio transmitters are required to be turned off at blasting sites. I remember a table giving safe distances for transmitters depending on their frequency and power, but can’t currently find it. As I use non-electric initiation, it’s not something I worry about anyway.
Ok, not the table I remembered, but found an ICI one from 1996.
A quick rundown ot the table: 5 to 25 watts, 50 metres min safe distance, with 50,000 to 100,000 watts having a min. safe distance of 3000 metres.
Now the plot thickens, found NZS 4403:1976, it separates AM and FM. AM is similar to above, though the 25 watt case is 30 metres. For a 1W to 10W FM transmitter, min safe distance is 1.5 metres.
So what is a cellphone? FM-like? With a max of 0.6W or is it less these days? I doubt it would induce enough current into a firing circuit to initiate it. Otherwise all IEDs fired by cellphone would go off when the cellphone tries to contact the tower.
And on preview, I see IntelSoldier has illuminated me with how IED’s are fired. Interesting. Perhaps they found cellphones do initiate their bombs before their time Ah, just thought of a better reason :smack:
My understanding is that this once was the case but no longer is. Cellular systems knows how to deal with a phone that’s “hitting” too many cells (basically, service is denied).
It can be greater. I was recently involved in a rescue following a plane crash, in which the injured pilot was able to talk on his cellphone. It was later determined that his call was processed by a tower over 30 miles from the crash site.
Administrator: Cellphones are not allowed on campus because they might set of bombs.
Doper student: Ah, excuse me, but aren’t bombs a much bigger problem than my cell phone?
Administrator: Never mind.
Furthermore, I think we can assume that the bomber is going to set off his bomb when it will cause maximum mayhem. Setting it off early is likely to be better not worse.
I am afraid it’s all going to change over the use of mobile phones on planes. A couple of airlines are planning (is is that threatening) to introduce systems which will allow passengers to use their phones while airborne . Story here :-
It’s not the controls that are interfered with, it’s the radios and navigation equipment, and as pointed out, it’s rare.
Nonetheless (and despite the Mythbusters episode) cellphones have on occassion disrupted airplane equipment. So far as I know, no crashes, but it could be a problem when flying in weather requiring flight by instruments (i.e. can’t see out the windows) as that requires precise navigation. For similar reason, you have to be careful about magnets being in a cockpit (compass interference)
But the real reason they’re a no-no on airplanes is the FCC, not the FAA. For ham radios and CB’s, for example, use on board is at the discretion of the pilot and either of those is more likely to cause a problem than is a cellphone.
Not too long ago I read an article (I don’t remember where) about this subject that suggested that there really was little to be gained by the airlines by allowing cell phone usage, and much to lose.
The author said that besides the obvious problem of the crew having to deal with annoying passengers who yak all day long and piss off their neighbors, the airlines would prefer that the passengers not be aware of events on the ground.
This second point is interesting: What if a family member died in an accident and a relative calls the passenger with the news? What if a passenger has a terrible fight over the phone that signals the end of their marriage?
It would be challenging to peacefully keep passengers cooped up in the plane after such a disturbing call.
Even on the most humdrum of days, there are thousands of flights in the United States. Statistically, among the many thousands of passengers in any given day, there must be several who, in an airplane-cellphone world, would receive distressing news while airborne that might hinder the crew’s ability to maintain calm.
Not to say that this is the true reason behind lack of enthusiasm from the airlines, but it is an interesting point to ponder.
Maybe more on target was the author’s discussion of the extreme cost of testing that would be needed to absolutely prove no risk, at the level of thoroughness demanded by the industry, contrasted with the minimal gain the airlines would see from it.
Nope. I gave it up and went back to working as an electronics tech. Research is kinda boring (even for Mythbusters) and I make more money as a tech, anyway.
They can plan and threaten all they want in Europe. But if they fly within US jurisdiction, the US FAA and FCC will enforce US regulations. And that currently means no cell phone use.
Ah, just thought of a better reason :smack: