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Shuai Chen
Section: 66804
Illumin Paper
Electromagnetic Interference: The Reason You Can’t Use Your Phone on Aircrafts
Electric fields can be produced by the voltages, and magnetic fields can be produced by electron flows.
Combining both the electrical field and magnetic field will result in electromagnetic fields (EMI). Even
though it is true that electromagnetic interference will not necessarily to bring down an aircraft from the
sky, theoretically, there are potential risks and concerns the EMI can create a problem
Introduction
Have you ever wondered that every time when you take a flight, why would the flight attendants
ask you to turn off your cell phone and other electronic devices? Or have you ever raised the
question that is it even possible to take down a ninety million airplane by your forty dollars IPod
Shuffle? It will not surprise me if you asked any question like that. It is very common today that
cell phones are banned during a flight. In the United States, the Federal Aviation Administration
(FAA) prohibited the usage of cell phones and other passenger electronic devices on the
aircrafts. Turkish Airline’s announcement states straight forwardly that “Mobile phones interfere
with the flight instruments and have a negative effect on flight safety.” [1] Even more, some
Chinese airlines prohibit all electronic devices during the flight. Today, most of the airlines
around the world have similar regulations. Even the most loosely aviation regulations include
banning the usage of electronic devices during take-off and landing. Most of people have a sense
that using cell phones and Wi-Fi in airplane is somehow dangerous, but they don’t know why.
The most common view today for banning electronic devices during takeoff and landing is these
devices may produce electromagnetic interference that interfere with the aircrafts’ navigation
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and communication systems, and therefore risks the plane and passengers in great danger. In
order to uncover more about how cell phones and other electronic devices will “messed up those
giant steel birds”, at first we have to know what electromagnetic interference (EMI) is.
What is Electromagnetic Interference?
Imagine that you are working or studying in a quiet room, but suddenly, somebody turned on a
vacuum cleaner. The sound that the vacuum cleaner makes is so loud that you cannot even focus
on your work. This is an example very similar to the electromagnetic interference. In high school
or college physics, students learn that electric fields can be produced by the voltages, and
magnetic fields can be produced by electron flows. Combining both the electrical field and
magnetic field will result in electromagnetic fields. EMI happens when the signals of
electromagnetic fields temporarily interfere with other devices that are planned to be used [2].
Even though, for some people, EMI seem to be a professional term that only applies in the
relevant fields, it actually exist surrounding our lives. Generally, there are two sources to cause
an electromagnetic interference. The first one is electromagnetic radiation, a fundamental
phenomenon that relates to the electromagnetic field, which is produced by moving charges.
Electromagnetic radiation are generated by outside sources can interrupt or degrade the
performance of an electrical circuit. A classic example of EMI by electromagnetic radiation in
our daily lives is when we put our cell phones or laptops
close to a radio that has been turned on, we often hear
continuous “beep” noises from the radio’s speaker. That is
because the electromagnetic fields of our cell phones or
Figure 1: Example of EMI on TV antenna system
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laptops interfere with the radio circuits. The second cause to generate EMI is electromagnetic
induction, which occurs when magnetic field is varying. Sometimes, EMI occurs on our TV
antenna systems (see Fig. 1) [3]. In this case, it probably means that the TV signals are being
distorted due to electromagnetic induction.
Today, one major technique to reduce
electromagnetic interference in a circuit is adding
shields on electronic devices. Taking coaxial cable
(see Fig. 2) as an example, the center core of the
cable is formed by conducting material [4]. Around
the core, there is a layer of insulated covers to block
Figure 2:Cross-section through a coaxial cable
showing shielding and other layers
external electric fields. This shielding technique is often known as Faraday Cage. The amount of
electromagnetic interference reduction is depends on the material and its thickness, the size of
shielded volume, and the frequency of the electric field. However, when we deal with EMI on
airplanes, apparently this technique is not that promising because it is impossible to shield every
part of the airplanes, and moreover their navigation and communication systems has to be
exposed to receive radio frequencies from the outside. Thus, if the current technology cannot
solve the EMI problem, then we should examine what risk that EMI will bring to the aircraft?
Can Your Cell Phone Really Bring down a plane?
As the question has been raised previously: is it even possible to take down a ninety million
dollar aircraft from the sky by using forty dollar IPod Shuffle? The answer is a no. If any
electronic device could do this much of damage, FAA or any other aviation related organization
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would prohibit consumers to carry electronic devices on board. In fact, according to a recent
CNN news report, so far there is no such an event suggested that “electromagnetic interference
from a portable electronic device brought down a commercial plane or was a contributing factor
in an accident.” In addition, based on a survey by the Consumer Electronic Association, about
one-third of airplane passengers admitted that they has left their electronic devices on during a
flight in the last year [5]. Giving a quick glance on these facts, it seems like if you do not follow
the rules that flight attendants tell you, there is no big deal. The real reason that cell phones are
impossible to bring down airplanes is because aircrafts control systems today are fully installed
within the planes and absolutely shielded to keep outside signals away [6]. However, even
though it is true that electromagnetic interference will not necessarily to bring down an aircraft
from the sky, theoretically, there are potential risks and concerns the EMI can create a problem.
Thus the attitude of EMI will not affect aircrafts is wrong.
How EMI can affect aircrafts?
Unlike the well protected aircrafts control systems, aircrafts navigation systems are especially
vulnerable. There are two reason for this: one is some parts of navigation systems are designed to
detect and act on outside signals. The other reason that navigation systems are vulnerable is
because radio based systems are very sensitive to even low level of interference [6]. Therefore,
electromagnetic interference to the navigation may potentially, although rare, affect aircrafts to
deviate from the correct course or raise pilots’ operation difficulties during critical phase of
flying (take-off and landing).
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Aircrafts communication systems are also exposed to the outside signal by the similar way if the
aircraft is under a serious EMI environment. Pilots communicate to the ground control, report the
planes positions to the air traffic control, and collect weather information with all sorts of radio
frequencies and different types of radars. If a consumer has his or her cell phone turned on, and
the frequencies it transmitted overlaps with any frequencies that aircrafts are used, false message
could be sent or received, which is hazardous to commercial aviation [7].
Nowadays, although scientists and engineers have proved in theory, electronic devices such as
cell phones and laptops are potential sources to cause EMI in aircrafts, there is still no clear
statistics showing what electronic devices will surely dangerous a commercial flight due to
electromagnetic interference. It is also impossible for flight attendants to check or scan every
consumer’s electronic devices before taking off. Therefore, the world consensus on making
regulations to ban electronic devices in airplanes are based on the principle “better safe than
sorry”.
Engineers are now seeking the solutions for EMI.
Just like the report that CNN news addressed in the end, “technology is creating a problem, and
technology is solving the problem.” In Europe, some regulations and technologies have allow
customers to use their phones in some limited commercial flights. On the other hand, facing the
pressure of competition, many other airlines in the world is moving toward to seek new
technologies to eliminate the barrier of EMI. In 2011, Emirates Airline start to provide Wi-Fi
access on its A380. Recently, Emirates OnAir system allows passengers to use their own cell
phones during the flight. Some American airlines now are also preparing to introduce new
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technologies to allow their passengers using
cell phones in air and now waiting for
permissions. Flights carry an equipment
called Pico cell (see Fig. 3), a small cellular
base station that can communicate send cell
phones frequencies in the aircrafts to
satellites or ground stations [8]. However,
Figure 3: Working diagram of Pico cell
the cost of using this on board calling
service will be higher and the transmission speed will be lower. The cover range of Pico cell
network is also small, but is enough to provide services on airplanes. Another company
AeroMobile also provides on-board cellphone services on commercial flights. Its equipment can
be installed while the planes are in manufacturing or in later upgrading. Currently there are
sixteen airlines are using AeroMobile services. AeroMobile has its own cellular operator, which
cell phone calls will be routed through satellites to the ground. In addition, AeroMobile will have
an EMI screen system to keep mobile phones and other electronic devices from trying to contact
with the ground-based networks. It is so far the best on-board cellphone services provider, and
handling EMI issue well in its operation.
Conclusion
Electromagnetic interference is a usual phenomenon in physics world. Relating it to aviation, it
can bring problems to both pilots and passengers. People today have realized it is time to invent
some new technologies to deal with these problems. We have reasons to believe, in the near
future, the problem of electromagnetic interference in aircrafts will be overcome by human’s
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wisdom. However, before we have fully solved this issue, we still need to pay attention on it.
During a flight, the interference by electromagnetic field on the aircrafts instruments may be
small, but the consequences can be high.
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Work Cited
[1] B. Strauss, M. G. Morgan, J Apt, and D. D. Stencil. (2006, Mar). Unsafe at Any Airspeed?
[On-line]. Available: http://spectrum.ieee.org/aerospace/aviation/unsafe-at-any-airspeed
[2] Electromagnetic Interference (EMI) Information [On-line]. Available:
http://www.bostonscientific.com/lifebeat-online/electromagnetic-interference.html
[3] B. Stallion. (2006). Electromagnetic Interference (EMI) on TV Antenna Systems
[On-line]. Available: http://www.tvantenna.com/support/tutorials/emi.html
[4] Modern Cable Technologies [On-line]. Available: http://truestats.biz/coacsial.html
[5] M. M. Ahlers and R. Marsh. (2014, Sep 23). Can Your Cell Phone Bring Down a Plane?
[On-line]. Available: http://www.cnn.com/2013/09/23/travel/cell-phones-devices-on-airplanes/
[6] P. B. Ladkin et al., “Electromagnetic Interference with Aircraft Systems: why worry?”
Bielefeld Univ., Bielefeld. Germany, Rep. RVS-J-97-03, Jul. 13, 1997.
[7] Why am I not allowed to use my cell phone in airplanes or hospitals? [On-line]. Available:
http://www.howstuffworks.com/question230.htm
[8] Approval for Mobiles on Aircraft [On-line]. Available:
http://news.bbc.co.uk/2/hi/7314362.stm