http://www.dailymail.co.uk/travel/travel_news/article-3527966/What-happens-don-t-switch-phone-aeroplane-mode-flight.html
What happens when you don't switch your phone to flight mode?
By Chris Kitching for MailOnline 12:50 07 Apr 2016, updated 20:38 07 Apr 2016
Some passengers falsely believe that a phone's signal can cause a crash
Experts said technology is becoming increasingly reliable and safe
A phone signal can interfere with radio communications in the cockpit
Airline passengers are repeatedly told to switch their mobile phones to flight
mode – but what happens if they don’t?
There’s a belief that a phone’s signal can interfere with important electrical
or telecommunications systems in the cockpit, but is it capable of causing a
plane to crash?
MailOnline Travel reveals what happens when passengers or crew don’t switch off
their phones during a flight.
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Most flights ban passengers from using their mobiles for voice calls or text
messaging once in the air
WHY YOU CAN’T USE YOUR MOBILE PHONE TO MAKE IN-FLIGHT CALLS
Most commercial flights don’t allow passengers to use their mobile phones to
make calls or send text messages in mid-air out of concerns over safety or the
comfort of everyone on board.
The ban was originally brought in over fears the radio frequency emitted by
mobiles belonging to passengers or crew could malfunction a plane’s electronic
systems.
This is not a problem with new phones and on-board systems such as picocells,
which aren’t widely used. But, on most flights, the ban remains in place.
Passengers are allowed to use their electronic devices, including smartphones
and tablets, during the entire duration of a flight, including the pre-flight
safety demonstration, as long as they have been switched to flight mode.
However, the rules may vary by airline.
Some international airlines have equipped some of their planes to allow voice
calls and texts in-flight, said the UK Civil Aviation Authority.
In the US, the Federal Communications Commission has banned airborne calls
using mobile phones since 1991 over concerns that they could disrupt towers on
the ground.
The FCC has reconsidered the ban, but lawmakers have argued for it to remain in
place solely for passenger comfort.
Those who travel by private jet, however, are usually permitted by the crew to
use their devices to communicate with the outside world.
Some passengers believe personal electronic devices such as mobile phones and
tablets need to be turned off because they could bring the plane down.
However, there is no evidence signals from passengers’ electronic devices have
ever caused a plane to malfunction and crash, and experts said modern
technology is safe and reliable.
If anything, a mobile that hasn’t been switched to flight mode may just annoy
pilots and air traffic controllers with an unpleasant sound.
It’s the same kind of noise that can be heard over speakers if a mobile is
nearby and it’s due to the phone’s powerful radio emissions.
Signals from mobile phones can interfere with radio communications between the
cockpit and control tower
HOW DOES A PICOCELL SYSTEM ALLOW IN-FLIGHT CALLS?
The system works using a small telecommunications base station called a
picocell.
A picocell is low cost and typically the size of a ream of A4 paper.
It acts as a miniature mobile telephone tower communicating with mobile phones
within the aircraft and relaying the signals to either satellites or a
land-based system.
Communication between the picocell and the rest of the telephone network is on
separate frequencies.
There is no interference with the aircraft's equipment as is the case with
on–board phone systems already on many commercial aircraft.
Interference is reduced because both the picocell's and the phones' output
power can be reduced to very low levels.
In a blog post for AirlineUpdates, a pilot wrote that transmitting mobiles can
and do cause audible interference on an aircraft’s radios, but it’s fairly rare.
The pilot added: ‘You’ve probably heard this interference yourself when a phone
is set near a speaker.
‘It sounds like a “dit-dit-dit-dit” tone and it’s pretty annoying.’
The pilot wrote that it doesn’t happen every time a phone is on inside a plane
and they fly 50 times a month and only hear it through their headphones once or
twice over that period.
The risk of interference has been drastically reduced by modern technology.
The pilot admitted interference is usually from a phone belonging to a crew
member who forgot to switch it to flight mode, given that the pilots and
forward flight attendants are seated closest to the radios.
If there is repeated interference from mobiles it could cause the flight crew
to miss a critical radio call from air traffic control, the pilot wrote, adding
that it happened on a recent flight as a passenger surreptitiously texted on
his phone.
The interference stopped once the passenger was told to turn on flight mode.
While most flights ban voice calls and text messages in-flight, some
international airlines have equipped some of their planes with
telecommunications base stations, or picocells, which operate at very low
power.
These specially-designed systems don't interfere with the flight crew's
communications.
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