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By Katia Moskvitch
The theory goes that mobile phones and other gadgets could interfere with
sensitive electronic systems. So why is it still so difficult to prove the
truth behind the claims?
I have a guilty secret to confess. My plane was preparing for take-off from
London s Heathrow Airport in March when a flight attendant made the usual
request for passengers to turn their electronic devices off. Far from
complying, I pushed my smartphone deeper into my pocket. I had important work
messages to check, and surely my little handset wasn t going to cause the plane
to plummet from the sky, was it?
It seems I'm not alone. A recent survey found around four out of 10 US air
passengers admitted they don t always turn their gadgets off on flights. One
notable occasion saw the actor Alec Baldwin reacting furiously on Twitter after
being kicked off a Los Angeles-to-New York flight before take off for refusing
to stop playing the online game Words With Friends on his phone.
According to regulations, which are pretty uniform around the world, the use of
portable electronic devices is not allowed below around 3,000m (10,000ft), even
in "flight mode which stops the transmission of signals. Above this height
devices like laptops and music players can be used, but phones must remain off.
These rules are important, we are told, to avoid potentially dangerous
interference between signals from these devices and sensitive onboard
electronic systems. But do these fears have any scientific basis, or is it time
to relax the rules?
The fear of interference comes from the fact that gadgets connect to the
internet or to mobile phone networks using radio waves. To explain the
theoretical dangers, Peter Ladkin, Professor of Computer Networks and
Distributed Systems at Bielefeld University, Germany, uses the analogy of
holding a blowtorch to your household heating pipes. The central heating system
in your house makes changes based on the readings of thermometers within those
pipes, so the blowtorch will heat the water, change the temperature readings
and trigger the system to make adjustments.
Personal mobile devices could act in a similar way on aeroplanes, on which
hundreds of electronics-based systems, known as avionics, are used for
navigation, to communicate with the ground and to keep track of the components
that keep them in the air. Some involve sensors that communicate information to
cockpit instruments. It's not just an issue with mobile phones. Kindles, iPods,
laptops, handheld gaming consoles they all emit radio waves. If these are at
frequencies close to those of the avionics, signals and readings could be
corrupted. This could affect systems such as radar, communications and
collision avoidance technology, and the problem is potentially magnified if
gadgets are damaged and start emitting stronger radio waves than they should,
or if signals from multiple devices combine.
So much for the theory, but is there any proof that this is a problem? There
are no known recorded incidents of crashes having been definitely caused by
such interference, but that said the causes of accidents can sometimes remain
unknown. A flight recorder may not identify that a critical system has failed
because of electromagnetic interference from passengers devices.
System malfunction
But while definite proof may be lacking, there is plenty of anecdotal evidence
that the risks should be taken seriously. A report summarising 50 cases of
safety issues thought to have been caused by personal electronic devices, was
published in January this year. These were compiled from the US Aviation Safety
Reporting System, a database maintained by Nasa, to which crew members can
anonymously submit reports of safety problems. One such case was summarised as
follows: "First Officer reports compass system malfunctions during initial
climb. When passengers are asked to verify that all electronic devices are
turned off the compass system returns to normal.
A 2006 analysis of the database identified 125 reports of interference from
electronic gadgets, of which 77 were defined as "highly correlated". In one
incident a 30-degree error in navigation equipment was immediately corrected
when a passenger turned off a portable DVD player. This problem reoccurred when
the device was switched back on. Fight crew have reported a number of similar
cases in which they have watched readings on navigations systems change
apparently in response to passengers being asked to turn specific devices on
and off. In another report, the International Air Transport Association (IATA)
identified 75 separate incidents of possible electronic interference that
pilots believe were linked to mobile phones and other electronic devices
between 2003 and 2009.
In the competitive world of aviation, some airlines such as Virgin Atlantic and
Delta Airlines have started advertising the use of technologies that allow
greater use of mobile devices on flights. In-flight mobile phone systems such
as OnAir and AeroMobile use miniature on-board base stations called picocells
which allow devices to transmit at lower power levels. Transmissions are
processed, transmitted to a satellite and then on to the normal ground
networks. This, says AeroMobile chief executive Kevin Rogers, enables the use
of mobiles as a roaming service just like when you go to a foreign country,
except that in a foreign country you don t need a satellite link. Some
airlines, such as Boeing, are now starting to fit AeroMobile equipment during
production.
These systems allow you to use your phone while at cruise altitude, but not
during take-off and landing. Rogers thinks that this might change one day, but
at the moment it is still difficult to prove categorically that there is
indeed no interference so airlines tend to err on the side of caution and be
conservative.
But as Rogers adds: Many phones are always left on anyway. If there was a real
risk of interference of a mobile phone or an iPad with the aircraft s systems,
people would not be allowed to take them on the aircraft at all.
Some air authorities remain unconvinced, however. In-air mobile services cannot
be used in US airspace, for example. The US Federal Aviation Administration has
come under pressure to relax its rules and last year set up a group of experts
to study the question. A decision is expected by the end of this year.
Richard Taylor, a spokesman of the UK s Civil Aviation Authority, believes it
is just a matter of time before we see more widespread use of mobile devices on
aircraft, but that calls will remain banned during take-off or landing for the
foreseeable future.
When regulators like us are convinced that an aircraft can be used safely even
with portable electronic devices being used in the cabin, that the signal being
emitted from the cabin at any stage of the flight can be safely absorbed
without affecting any of the aircraft systems, of course the rules will be
relaxed, he says. But it s up to the manufacturers, and of course to the
airlines, to prove that they are operating the aircraft safely.
Perhaps that day may come soon. However, having learnt how difficult it is to
prove definitively that planes are safe from interference, I'll be making sure
my phone is properly switched off in future. After all, when I'm en route to my
holiday in the sun, I don't want my handset to be responsible for tricking the
pilot into landing in some rainy old place. Or for something even worse.
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