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Are personal electronics (of present or recent past; e.g. cell phones, mp3 players, iPads) a risk to commercial air travel? Is the typical request to "turn off all personal electronic devices" based on any reasonable data?

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    Don't have a source for this so I'm putting it in a comment, but keep in mind the EMF the airplane experiences from e.g. space -- the electronics must be shielded for that reason alone. Therefore I find it highly unlikely that any type of consumer electronic device would have any affect on avionics. Plus there are no known cases of these devices causing a problem. (But I don't have sources so I'm not going to put this as an answer) – Billy ONeal Mar 22 '11 at 15:01
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    I'm not going to be able to give a better answer than those that has answered. But if mobile phones really was a danger to aviation do anyone actually think they would let you board with one? You can't bloody well bring water on the plane anymore... – Kit Sunde Mar 22 '11 at 17:14
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    Commenting here, because this keeps coming up in answers. Confiscation (lack thereof) is not an issue. Lots of items much more dangerous than cell phones are not confiscated (lithium batteries). Lack of confiscation does not indicate lack of risk. – Russell Steen Mar 22 '11 at 19:21
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    @Billy ONeal: EMF from space is coming from outside, like blizzards, but the plane builds a Faraday cage. Consumer electronics are inside the plane. Should make a difference, no? – user unknown Mar 23 '11 at 0:07
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    @user unknown: It is possible to make and receive phone calls if you turned on your cellphone inside the plane (of course while the plane is still on land and in the range of a cell tower). If a plane's body truly acted as a Faraday cage, a phone should receive no (or lowered) signal inside a plane. – Lie Ryan Mar 26 '11 at 19:32
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From ABC News (2007):

An aviation safety database maintained by NASA shows a handful of incidents each year reported by pilots who suspected cell phones and other electronic devices had caused a problem during flight. Despite these reports, not a single air crash has been proven to be caused by the use of a cell phone onboard a plane.

John Nance, an ABC News consultant and veteran airline pilot, says there's little reason to worry about cell phones interfering with an airplane's navigational equipment. He says an airplane's electronic systems are "all heavily shielded. That means that stray signals cannot get into those systems."

The airlines can't allow cell phones to be used in flight until the technology has been proven safe. However, according to Nance, the Federal Communications Commission and the Federal Aviation Administration "have not done their job over about a 25-year period. And the airlines have quite properly said … if you're not going to tell us, then we're just going to default to the most conservative position and say we're not going to use them in the air."

Here is a study done in 2003 that concludes "Cellphones and other electronics are more of a risk than you think"

regulations already permit a wide variety of other portable electronic devices--from game machines to laptops with Wi-Fi cards--to be used in the air today. Yet our research has found that these items can interrupt the normal operation of key cockpit instruments, especially Global Positioning System (GPS) receivers, which are increasingly vital to safe landings.

...

There is no smoking gun to this story: there is no definitive instance of an air accident known to have been caused by a passenger's use of an electronic device. Nonetheless, although it is impossible to say that such use has contributed to air accidents in the past, the data also make it impossible to rule it out completely.

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Consumer devices that meet FCC emission limits can exceed safe interference limits set by the FAA for avionics, because the FCC and the FAA do not harmonize their regulations.

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At present, we believe that passenger use of electronics on board commercial aircraft should continue to be limited and that passengers should not be allowed to operate intentionally radiating devices such as cellphones and wireless computer equipment during critical stages of flight.

Let's presume there is a 0.01% chance that cell phones can cause a crash. Worldwide there will surely be more than 10.000 flights per day. So even with such a low percentage it would mean at least one crash per day. Looking at it this way I can understand the ban.

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    100% kudos to the FAA for NOT waiting until there is an accident before taking action. – DJClayworth Mar 22 '11 at 15:30
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    How does this reconcile with international airlines such as Emirates Air allowing cellphones to be used during flights? Do they not care about safety? This would be surprising to me, given that they have one of the best safety records, and have never had a fatality in over a million flights. I'm not sure I'd want to fly in a plane that would drop out of the sky when someone turned on their phone, even if it was a million-to-one shot. For an airline to say that seems ridiculous. – Ezra Mar 22 '11 at 17:02
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    Cell phones are prohibited so the fact that no accidents have happened while prohibited and thus low usage does not demonstrate that full use is risk free. – jjj Mar 22 '11 at 18:51
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    Something that results in a crash per day is not a low risk percentage. Clearly, because we don't have a crash per day, the industry/government players restrict and maintain things that remove risks that are less likely than .01%. Your percentage "proof" is a strawman argument. – Russell Steen Mar 22 '11 at 19:16
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    @Russell - my "percentage proof" wasn't intended as a proof, but as an attempt to explain why there is a ban. As long as there is even a small chance that cell phones can do harm, due to the large number of flights, it could still cause the loss of many lives. – Oliver_C Mar 22 '11 at 20:03
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Cell phones present a separate category, as they actively and intentionally transmit (i.e. generate E-M field), while the other appliances produce only a E-M noise, which is a lot weaker, see Small Aircraft RF Interference Path Loss:

For various reasons, many devices such as laptop computers are allowed during flights, while intentional transmitters such as wireless devices and phones are prohibited.

One particular issue with cell phones is that when they get far from the ground station (or lose connection to the ground station), they transmit a lot stronger signal to maintain the connection or to discover a station (the transmitted signal power varies in range 20 mW - 3 W, see also Mobile phone radiation). While one cell phone doing this would still most likely still be quite weak, having 400 cell phones transmitting at full intensity is something which could create an interference. This also explains why phones are not "confiscated" (like a knife would be) - a few of them left active does not matter, but having many of them could.

Besides of aircraft safety there are other concerns: active cells phones in the plane are bad for the phone operators, as the ground infrastructure is not designed for a situation like this. While the phone is quite far, it has a direct visual connection to many ground stations. See Mobile Phones and Aircraft

As the number of lines available in a particular cell is limited, the cells are sized according to the predicted number of simultaneous users. Inner-city cells are smaller than rural ones, based on the likelihood that there will be a greater demand for lines. Consequently, there are more cells per unit area in cities than elsewhere. It is also worth noting that the line-of-sight link from a mobile phone to a particular base station in a city is likely to be obstructed by buildings.

An aircraft could be carrying 500 cellphones. While passing directly over a city and thus unhindered by buildings, these phones could be in the line-of-sight of hundreds of base stations and could try to register with all of them. This would impose a temporary but extreme load on the network. The speed of the plane passing over the small inner-city cells would also result in an unusually rapid handover from cell to cell, possibly far in excess of the network's design limits.

It would be possible to provide an infrastructure on the plane to avoid the issues above, by having a dedicated station on the plane, which phones on board would connect to (this can be done with a weak signal, and with no need of any handover during the flight), and this station would then connect by one link to the ground network by some special means, e.g. using a satellite link. One paper attempting to design a scheme like this is ETSI White Paper No. 4, GSM operation onboard aircraft.

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    great answer. These are both the reasons I know. I also can add I have an engineer friend that went to school with me whom works for american airlines. If they want to allow an intentional radiator on the plane they have to get it certified safe. This requires a test flight. This is a very very large cost, and they have to do it per phone model, they consider it cost prohibitive and just ban phones as to avoid retesting constantly. – Kortuk Mar 24 '11 at 6:37
  • the reasoning as to why the higher cell density in cities is not complete. Another overriding reason is the shorter range due to signal deterioration in and around buildings. That's also why towers are often placed such as to have a clear line of sight down roads, rather than in blind corners. – jwenting Oct 4 '11 at 8:45
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The FAA regulation is based on a study from the RTCA which does indicate that cell phones can interfere with critical systems.

Clearly they do not interfere every time, and not every interference would result in a crash, and proof after the fact would be difficult. So the fact that no crashes have been blamed on this is not, by itself, proof that they pose no risk.

As to why all devices might be banned, airlines tend to err on the side of less lawsuits and less violations. The regulatory policy is clear that Airlines (in the US) are responsible for the effects of electronic devices operated on their planes, so they are going to be very hesitant to allow usage -- especially since research by the RTCA shows that some devices do interfere.

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    The airlines don't have a choice anyways on the cell phones. The FCC says "thou shalt not use cellphones in flight". Other electronic equipment is restricted by FAA requirements (which varies based on IFR or VFR flight, and sometimes by what the PIC chooses to allow). – Brian Knoblauch Mar 24 '11 at 20:07
  • another reason for a blanket ban is the impossibility of testing and verifying each and every piece of electronics a potential passenger might have in his posession, let alone training flight attendants to recognise and differentiate between all of them (often placed in covers, bags, skins) and remember which are or are not allowed. And situations like "yes sir, your eReader has to be turned off because it has a WiFi transmitter, the person next to you has a different model without such a transmitter so it is ok" isn't going to go down well with many passengers either. – jwenting Oct 4 '11 at 8:48
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It appears it is based on reasonable data. I have no knowledge about any FAA research, but (not so recently) the Mythbusters tackled the myth that it is forbidden to use cellphones to force you to use the on-board phones.

They had to build their own mock-up cockpit and throw a whole lot of interference-causing stuff at it, which sort of worked. However it supposedly only worked because the wires in their mock-up weren't properly shielded. This would be supported by their failure to cause any sort of interference in a corporate jet (a Hawker 800XP).

  • It's not just a matter of poor shielding. You can't shield the antennas of the radionavigation equipment. If some random poorly-manufactured (or damaged) device just happens to start emitting noise on the frequency used by the localizer or glideslope, they can throw off the ILS readings, which is extremely unhelpful when you're trying to land in low visibility conditions. ILS is still a surprisingly-simplistic system that isn't very difficult to fool. It's literally just a couple of directional AM signals and a measurement of their interference pattern (designed in the 1930s or 40s, IIRC.) – reirab Jan 9 '15 at 17:39
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As to no reported incidents, there is at least one. It was due to a passenger's refusal to turn off a boom box which interfered with the aircraft's navigational equipment. See, US v. Hicks, 980 F. 2d 963 (5th Cir.1992) retrieved from: https://scholar.google.co.th/scholar_case?case=6625292697406630772&q=boombox+interference+with+flight+crew&hl=en&as_sdt=2003

  • Welcome to Skeptics! This is poor evidence. It consists of a pilot committing a "post hoc ergo propter hoc" fallacy. It doesn't show that the boom box actually interfered with the aircraft's navigational equipment. – Oddthinking Aug 23 '18 at 15:14
  • It was not merely a question of the pilot's personal views. Federal officers made an arrest. Evidence was presented to a grand jury, which returned an indictment. A trial was had before a judge and jury. And Mr. Hicks was convicted based on the evidence. It may be "poor evidence" but it was sufficient enough to deprive him of his liberty for a term of years. – Michael Kane Sep 11 '18 at 12:21

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