What is electromagnetic interference and what problems can it cause in the aircraft?

Answer 1

Ok, electromagnetic interference is the fact that a current carrying inductor can induce a current in a nearby object. If a current carrying conductor, ie a wire, carrys a current it creates a magnetic field. The opposite can also occur where a magnetic field can induce a current in a current carrying inductor. Now, lets apply it to say, a mobile phone, ever been near a speaker and receive a text message or a call, the speaker seems to make this funny sound, your mobile is creating a magnetic field that induces into the speaker windings creating a magnetic field because it is a coil in the speaker and thus makes the cone of the speaker move. Lets take your mobile phone onto the aircraft shall we.... You are flying 40,000 feet up and for some impossibility you receive a phone call, or more likely, your phone trys to find the nearest tower by upping its output. It induces a voltage /current in any current capable conductor, lets say next to your seat is the aircrafts navigation sensors, it induces a current in that and the computer on the plane gets the wrong reading, too high or too low, it changes what the computer displays and you decide to fly into a mountin because the pilot changes course because of incorrect readings. In actual fact the number of incidents because of mobiles etc on aircraft are small, think they have only caused one crash. This is why you use shielding, ie cover the wire with a metallic sheath, the inducted field conducts onto the shieth, protecting the cable and transferring it to the planes 'ground'

Hope this helps.