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There seems to be a lot of debate behind the cell phone usage ban on airplanes. A lot of cell phones now have airplane modes so we can enjoy out electronic devices in peace while aboard commercial aircraft. We keep hearing how cell phone communication could interfere with the aircraft instruments and devices. The ban was put into place in 1991 and was almost lifted in 2007, but was upheld by the FCC. I am curious what devices technically do they interfere with? What exact instruments do cell phones radio frequencies potentially interfere with? What on an aircraft uses similar radio frequencies? Or is it all just a general concern since there is a lot of electronic communication that needs to take place for an aircraft to operate safely?

EDIT: This could apply to smart phones, laptop data cards, and other devices (Kindle, etc.) that connects to the cell networks while on aircraft.

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closed as off topic by TheTXI Aug 10 '09 at 17:02

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@TheTXI I agree with you partialy with this not being computer related, but with all the smart phones and data laptop cards out there, I figured this was computer related as cellular networks are being used by computers all the time. Just a thought. –  Troggy Aug 10 '09 at 17:43
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7 Answers 7

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Basically cell phones generate a lot of electromagnetic noise. When a conductor is in a changing magnetic (or electormagnetic) field a current will be induced. That's the basic reason why cell phones can interfere with instruments, basically with everything that involves signals passed over wires.

Nowadays most wires and instruments are properly shielded (as cell phones are not the only source of electromagnetic stuff and it's better to take precautions before anything goes wrong.

That's probably also why the ban is still in place, as it is better to be safe than sorry. The Mythbusters once ran a few tests and concluded that cell phones can and will interfere with certain instruments in an airplane, though they couldn't reproduce it with a recently-built aircraft. But risking one case where instruments are not properly shielded and an aircraft goes down is probably worse than simply banning all cell phones.

Similar reasons go for medical equipment in hospitals.

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99% of cell phones (and all electronic devices) will cause absolutely zero ill effects on an airplane.

They ask you to keep your phone and other radio equipment off to make sure that the other 1% does not interfere with any of the airliner's communication equipment. It's to make absolutely sure that the plane can operate safely with no outside interference they have to deal with.

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Yeh, who would want to fly in an airplane if 1 out of every 100 flights went down due to that 1% problem ;) –  AaronLS Feb 5 '10 at 12:42
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I'd say cell phones cause almost no interference. After all, do you think everyone remembers to turn off their phones before take off? It's not like the airlines have a way to check.

The fact that most passengers can't be bothered to put their seats upright tells me that there are plenty who don't turn off their phone as well. And since airplanes haven't been falling from the sky, I'd say interference is nil.

The real reason is because it would be too disruptive for other passengers to have all kinds of people yakking in their phones.

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That is the stupidest argument I've ever heard in my life. There have been cases of plane crashes where cell phone use was strongly implicated, but never proven. Just because most of the time it doesn't interfere doesn't mean it will never interfere. If you were on one of those crashes, you probably wouldn't feel so smug. –  Paul Tomblin Aug 10 '09 at 18:01
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I'm not aware of any crashes where cell phone use was strongly implicated but never proven. I'm far more aware of countless cases of cell phone use on a plane with no effect whatsoever. Care to share any references? As I and others have said, if cell phones really cause a problem do you think the airlines (or FAA) would just rely on asking us to turn off our phones? Seriously? –  Paul Lefebvre Aug 12 '09 at 0:44
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Although not an answer to your question, I do believe that even if you were allowed to use your cell phones, you would have serious problems with the service. When you move between cells, your signal is handed off to the next cell - traveling that high & fast, I believe you would mostly likely have serious hand off problems.

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Two things to consider, somewhat contradicting each other.

1) If it were really true that cell phones could have a serious affect, the FAA would simply mandate that all airplane equipment be shielded such that it cannot be affected by cell phones. This is usually how the FAA works. It does not rely on sheep (aka Passengers) to actually listen and turn off their phones (as noted by Paul L in another answer).

The FAA is severely uptight about airplane safety and security!

2) Using a Blackberry as an example, put it next to a telephone (Old IBM ROLM PBX phones are REALLY vulnerable to this) and send yourself an email. You will soon hear some crazy interference, off the HUNG UP phone!

Some laptops experience this as well. Leave your BB sitting next to it, and as certain data packets come in, the laptop speakers make some odd noises, even when muted.

So clearly there really is a possibility of interference. Now whether it is sufficient to be problematic, I think the FAA's laxity on this issue answers that question.

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This phenomenon is called resonant harmonics. What is happening when you hear this sound is the transmitted signal is inducing a current in the wire which is connected to the audio amplifier within your computer. While most of the time limiting the input gain is sufficient to control volume, these controls are useless when the resonance is produced between the input circuit and the amplifier. The amplifier is boosting the noise that is effectively introduced after the input circuit. This is a symptom of poor shielding to be sure. –  Axxmasterr Aug 10 '09 at 15:29
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The problem with saying "airplane equipment be shielded" is that most of that equipment needs to receive electromagnetic signals. If it can receive a correct signal from a ground based navigation station, it can receive an incorrect signal from a cell phone that's causing resonance with something else. –  Paul Tomblin Aug 10 '09 at 18:04
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The resonant harmonic phenomenon exists for all cell phones that use the GSM standard. See google.com/search?q=GSM+buzz –  las3rjock Aug 10 '09 at 18:36
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Awesome! I never knew the name for it! I did not associate it with GSM vs CDMA either. Thanks for the info! That is great stuff to know! –  geoffc Aug 10 '09 at 19:16
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@geoffc I will not exclude the possibility that CDMA phones can cause audio interference, but GSM phones are notorious for doing so, as the Google search illustrates. –  las3rjock Aug 10 '09 at 21:35
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It isn't due to interference with one instrument, it is that each and every phone can be different and they are not thoroughly tested.

It can be any and all devices if the cables used throughout the plane are not properly EM shielded.

That being said, the main reason for this is just existing laws and there are a few airlines who are starting to allow passengers to use their phone in air (for a much higher price!).

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This is a good point. You could have many international devices being used that are not regulated. –  Troggy Aug 11 '09 at 16:26
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Cell phones won't interfere with the plane's instrumentation. The main reason they aren't allowed is because the cell phone carriers don't like to deal with all the small charges generated by the phones switching cells as they fly over them.

It's just another silly government regulation that defies logic.

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It defies logic because there isn't any. There isn't any logic because it's stupid. Phone carriers own the cell towers, they don't get charged when they switch towers, and when they do, they charge roaming. Airliners don't care in the slightest how much money cell companies make. –  Grant Aug 10 '09 at 19:27
    
Yep, but obviously the FAA cares (illogically). –  Lance Roberts May 26 at 2:01
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