As the use of portable electronic devices (PEDs) has boomed, so have complaints about restrictions on their use, especially during airplane takeoff and landing. These regulations arose out of concern that radio emissions from PEDs might interfere with aircraft electronics systems. Takeoff and landing are critical times during a flight, and they require the crew’s full attention, constant communication with air traffic control and the correct functioning of all instruments. Opponents of these restrictions claim that the use of devices such as cell phones has not been shown definitively to have an effect on any operations of the aircraft. The Federal Aviation Administration (FAA) in the US and similar organizations in other countries have been taking the “better safe than sorry” approach.
Regulations
As of 2013, FAA regulations state that cell phones are not to be used at any time during a flight, and most other PEDs, such as laptops, CD players and game machines, must be switched off during takeoff and landing. In most cases, the takeoff and landing periods are defined as while the airplane is below 10,000 ft (3,048 m). On average, an aircraft takes about 15-20 minutes to reach this altitude, so the restrictions only apply for two relatively short periods at the start and end of the flight. There are some devices that are exempt, including heart pacemakers, hearing aids and electric shavers, as these are known not to cause interference. The ban dates originally from 1988 and was intended not only to prevent radio interference, but also to avoid the possibility of injuries caused by PEDs flying around or passengers’ attention being distracted during safety demonstrations.
In August 2012, it was announced that the FAA was to reconsider its restrictions on the use of PEDs, although the ban on cell phone use would remain. A study group was set up to look into testing methods and determine which, if any, devices can be used safely. As of 2013, The FAA is awaiting the group’s recommendations.
Many modern airplanes have WiFi systems that allow passengers to access the Internet via laptops and other devices. These systems are tested for compatibility with aircraft electronics and must be approved by the FAA. The making of calls using Voice-over-Internet-Protocol (VoIP) applications, however, is not permitted, in order not to cause irritation to other passengers.
Aircraft Electronic Systems
Airplanes contain a number of electronic systems to enable communication with the ground, assist with navigation and monitor the behavior of crucial components and equipment. These systems are collectively known as avionics. Many of them involve the transmission and receipt of radio signals and are therefore potentially susceptible to interference from devices that produce radio waves at similar frequencies. Radio frequency radiation can also induce electrical currents in wiring, so other avionics systems could be affected.
Avionics in modern airplanes are shielded from interference, but older planes that lack adequate screening may still be in service and, in any case, shielding cannot be comprehensive. The systems that use external antennae to receive signals are most at risk from interference as they are designed to pick up very weak signals and cannot be shielded. The aluminum frame of an aircraft can screen out radio waves, but there are gaps, such as the windows, through which interfering signals can pass and be picked up by antennae outside. The frame can also act as a resonant cavity, which amplifies signals from PEDs.
Portable Electronic Devices and Their Effects
All electrical equipment produces radio waves, whether this is intentional or not. Cell phones and devices connected to the Internet must do so to communicate with other devices. Perhaps less well known is the fact that CD and MP3 players, for example, also emit electromagnetic radiation at radio frequencies. PEDs have been shown to be capable of producing emissions through most of the radio spectrum used by aircraft systems. There is no proof that these can actually interfere with avionics, but there are a number of documented incidents, reported by pilots and other airline staff, that strongly suggest such interference.
There are a huge variety of portable electronic devices of various types and brands and checking the strength and frequencies of the emissions of each and every one is impractical. Although there is no conclusive evidence that PED emissions can interfere with systems in modern aircraft, there are too many unknowns for them to be considered safe for use at crucial times, such as takeoff and landing. While some devices, such as laptops, have built-in electronic shielding, this may deteriorate over time, get damaged or be removed and not replaced during an upgrade, so it cannot be guaranteed that they will not produce emissions. Since it is not feasible to check all individual PEDs for compatibility with aircraft systems, a ban on the use of all such devices below 10,000 ft (3048 m) is regarded as the most sensible option.
Cell phones transmit strong signals that can be received at great distances. This raises the possibility that they could interfere not only with aircraft systems, but also with ground-based communication at airports. This is the reason why their use is banned throughout a flight. Many modern cell phones have an “airplane” mode, which prevents calls being made, but allows some other functions to be used, such as playing games. Use of phones in this mode may be permitted, but it is left up to individual airlines.