Technology: Personal stereos take to the skies

2019-02-28 04:05:14

Apocryphal tales abound about airliners nearly crashing because passengers’ personal stereos, laptop computers or other electronic gadgets interfere with the plane’s navigation system. But there is no reliable evidence that this has ever happened, and the US Federal Aviation Administration is this month relaxing its regulations and allowing passengers to use electronic equipment while in flight. It is also setting up a reporting procedure for any interference that may occur. Scares about interference began around 1960, with worries about some portable radios. Oscillators in FM radios generate a high-frequency signal, and this could interfere with the instrument landing system that aircraft rely on in poor visibility. In May 1961, the FAA banned the use of FM radios in aircraft, and later extended this to all other portable electronic devices. New portable electronic devices are continually appearing, and their effect depends on where in the aircraft they are being used, and what the gadget and the aircraft’s electronics are doing at any given time. Meanwhile, aircraft manufacturers were building better shielding around their equipment to protect it from interference. The FAA’s Radio Technical Commission for Aeronautics reviewed the situation and in 1988 published a report saying that the practical risk of interference was ‘extremely low’. At the moment, different airlines and aircrews around the world have different policies, so passengers never know what gadgets they can or cannot use and when. The FAA has now issued an advisory circular which allows airline passengers to use portable electronic equipment except during landing and takeoff, in case it prevents passengers responding quickly in an emergency. Also passengers must be asked to turn their equipment off if there is any suspicion that it is causing interference. The crew must then report the incident to the FAA’s local Flight Standards District Office, so that information can be collated. The use of cellular phones while airborne will continue to be forbidden. Mobile phones transmit radio signals with a power of up to 10 watts. Even if the phone’s frequency, usually around 900 megahertz, does not clash with the frequency of an aircraft’s communication or navigation equipment, the network of wiring hidden in the aircraft’s body can act as an aerial and pick up the cellphone’s transmissions, possibly converting them into random noise. This noise could swamp the digital signals which the wiring is meant to carry. The FAA is, however, allowing passengers to use cellphones while the aircraft is on the ground, at the discretion of the crew. Britain’s Civil Aviation Authority is advising aircrew to check the cabin if they experience any problems. Otherwise there is to be no restriction except on cellphones,