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Electromagnetic Interference from Personal Electronic Devices
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Most regulators ban the use of transmitting personal electronic devices (T-PEDs), including mobile phones, in flight. The use of other, non-transmitting, personal electronic devices (PEDs) is not allowed during critical phases of flight (takeoff, climb, approach and landing). There are several flight safety related reasons for this:
- Active radio transmitters, such as mobile phones, and non-transmitting electronics, including virtually all electronic devices, emit electromagnetic radiation which could interfere with aircraft avionics.
- Some mobile phone systems cause interference on aircraft radios and intercom systems. This can be very irritating to the crew and disrupt communication.
- During critical phases of flight, it is important that the cabin crew are able to communicate with the passengers, provide information and issue safety instructions to them. It is therefore good practice to prohibit the use of PEDs at this point in the flight.
The ground networks that support mobile phones are not designed to handle connections from phones travelling at high speed or at a height where they are able to connect to several different masts simultaneously. The use of mobile phones in flight therefore causes network problems and additional costs for service providers. Although not a flight safety issue, it is a further consideration influencing the ban on use of mobile phones in-flight.
Interpretation and compliance with regulations is left to the aircraft operator. Most interpret "critical phases of flight" as below 10,000 ft or 3,000 m and prohibit use from when the doors are closed.
Increasing numbers of aircraft are fitted with WiFi enabling passengers to access the Internet in flight. It is common for such access to again be restricted to when the aircraft is above 10,000 feet or only made available at the same time as the in-flight entertainment system.
Some regulators are allowing the use of mobile phones on the taxi-in, after the aircraft has cleared the active runway, provided that the operator can provide evidence that there is no significant risk of interference to critical aircraft systems.
The level of electro-magnetic radiation from an individual PED might be low but there is concern that, with so many devices being carried in the cabin, the cumulative amount of radiation might be significant. There is no evidence that PEDs have been the cause of interference or malfunction of aircraft systems but, likewise, few of these devices have been cleared as safe for operation on an aircraft while airborne.
When a mobile phone in the cabin of an aircraft communicates with a ground station several miles below, it will have to transmit at maximum power to be received, thereby increasing the risk of interference with aircraft systems.
All electronic devices fitted to, or carried on, an aeroplane need to comply with appropriate airworthiness certification requirements to ensure the highest margins of safety. Clearly, it is impractical and probably unnecessary to certify all PEDs for use onboard an aircraft.
Current airline policy serves to mitigate the potential threat posed by radiation from PEDs but many passengers ignore instructions not to use them, despite cabin crew instructions and with absolutely no understanding of the science or aircraft systems.
- Flight Safe Mode: Most T-PEDs are now equipped with a "flight safe mode" which allows the user to disable/suspend the device's transmitting functions while still permitting other functions that do not require signal transmission.
- Picocells: To enable passengers to use mobile phones in flight, some airlines are fitting a device known as a picocell; the picocell acts as a miniature mobile telephone tower communicating with mobile phones within the aircraft and relaying the signals to either satellites or a terrestrial-based system. The picocell is designed and maintained for full compatibility with the rest of the on-board avionics. Communication between the picocell and the rest of the telephone network is on separate frequencies that do not interfere with either the cellular system or the aircraft's avionics much like the on–board phone systems already aboard many commercial aircraft. Since the picocell's antennas within the aircraft would be very close to the passengers and inside the aircraft's fuselage both the picocell's and the phones' output power can be reduced to very low levels reducing the chance for interference.
- AC 91-21.1B "Use of Portable Electronic Devices Aboard Aircraft" - FAA
- CAP 756 "Portable Electronic Device Generated Electro-magnetic Fields on board a Large Transport Aeroplane" - UK CAA
- "The airline passenger - a partner in the safety management system or an obstacle to it?" - article in HindSight 9, July 2009. This article, written by John Barrass in conjunction with Professor Robert Bor, looks at passenger behaviour and attitude to safety.