Mobile phones on aircraft

In the U.S., Federal Communications Commission (FCC) and Federal Aviation Administration (FAA) regulations prohibit the use of mobile phones aboard aircraft in flight. In Europe, regulations and technology have allowed the limited introduction of the use of passenger mobile phones on some commercial flights, and elsewhere in the world many Airlines are moving towards allowing mobile phone use in flight. Many airlines still do not allow the use of mobile phones on aircraft. Those that do often ban the use of mobile phones during take-off and landing.

On the one hand many passengers are pressing the airlines and government to allow and deregulate mobile phone use, while some airlines, under the pressure of competition, are also pushing for deregulation or seeking new technology which could solve the present problems. On the other hand, official aviation agencies and safety boards are resisting any relaxation of the present safety rules unless and until it can be conclusively shown that it would be safe to do so. There are both technical and social factors which make the issues more complex than a simple discussion of safety versus hazard.

The debate on safety

In the United States, the use of mobile phones and similar devices on airborne aircraft has been banned by the Federal Communications Commission.

One report asserts correlations between the use of mobile phones and other portable electronic devices in flight, and various problems with avionics. Another study concluded that some "portable electronic devices" used in the cabin can exceed the aircraft manufacturer's permissible emission levels for safety with regard to some avionics. On the other hand, a direct link between such devices and actual RF interference with aircraft systems has not been scientifically proven. Most reported incidents to date have been impossible to reproduce in tests.

Since these regulations were originally imposed by various international aviation agencies, ultra-low-power devices, such as picocells, have been developed. Reasons for this include improved security, reduction of interference, reduced health risks and to allow safe in-flight use of mobile phones. Many airline companies have now added such equipment to their aircraft. More are expected to do so in the coming years.

Electromagnetic interference

Electromagnetic interference to aircraft systems is the most common argument offered for banning mobile phones (and other passenger electronic devices) on planes.^{[citation needed]} Theoretically, active radio transmitters such as mobile phones, walkie–talkies, portable computers or gaming devices may interfere with the aircraft. Non-transmitting electronic devices also emit electromagnetic radiation, although typically at a lower power level, and could also theoretically affect the aircraft electronics. Collectively, any of these may be referred to as portable electronic devices (PEDs).

A NASA publication details the fifty most recent reports to the Aviation Safety Reporting System (ASRS) regarding "avionics problems that may result from the influence of passenger electronic devices." The nature of these reports varies widely. Some merely describe passengers' interactions with flight crews when asked to stop using an electronic device. Other reports amount to crews reporting an anomaly experienced at the same time a passenger was witnessed using a mobile phone. A few reports state that interference to aircraft systems was observed to appear and disappear as that particular suspect device was turned on and off. Another study describes a clear link where a passenger's DVD player induced a 30 degree error in the display of the aircraft's heading, each time the player was switched on.

A 2003 study involved three months of testing with RF spectrum analyzers and other instruments aboard regular commercial flights, and one passage reads:

...our research has found that these items can interrupt the normal operation of key cockpit instruments, especially Global Positioning System (GPS) receivers, which are increasingly vital to safe landings. Two different studies by NASA further support the idea that passengers' electronic devices dangerously produce interference in a way that reduces the safety margins for critical avionics systems.
There is no smoking gun to this story: there is no definitive instance of an air accident known to have been caused by a passenger's use of an electronic device. Nonetheless, although it is impossible to say that such use has contributed to air accidents in the past, the data also make it impossible to rule it out completely. More importantly, the data support a conclusion that continued use of portable RF-emitting devices such as cell phones will, in all likelihood, someday cause an accident by interfering with critical cockpit instruments such as GPS receivers. This much is certain: there exists a greater potential for problems than was previously believed.

A 2000 study by the British Civil Aviation Authority found that a mobile phone, when used near the cockpit or other avionics equipment location, will exceed safety levels for older equipment (compliant with 1984 standards). Such equipment is still in use, even in new aircraft. Therefore, the report concludes, the current policy, which restricts the use of mobile phones on all aircraft while the engines are running, should remain in force.

Critics of the ban doubt that small battery-powered devices would have any significant influence on a commercial jetliner's shielded electronic systems. Safety researchers Tekla S. Perry and Linda Geppert point out that shielding and other protections degrade with increasing age, cycles of use, and even some maintenance procedures, as is also true of the shielding in PEDs, including mobile phones.

Several reports argue both sides of the issue in the same article; on the one hand they highlight the lack of definite evidence of mobile phones causing significant interference, while on the other hand they point out that caution in maintaining restrictions on using mobile phones and other PEDs in flight is the safer course to take.

Health concerns

Following OnAir's series of tests that showed electromagnetic radiation of onboard GSM mobiles being lower than 1% of the limits endorsed by the World Health Organization and so significantly undercutting radiation levels of common terrestrial emission levels, inflight usage of mobile phones is considered harmless to passengers' health.

The debate on other issues

Social resistance to mobile phone use on flights

Many people may prefer a ban on mobile phone use in flight as it prevents undue amounts of noise from mobile phone chatter. AT&T has suggested that in-flight mobile phone restrictions should remain in place in the interests of reducing the nuisance to other passengers caused by someone talking on a mobile phone near them.

Competition for airlines' in-flight phone service

Skeptics of the ban have suggested that the airlines support the ban because they do not want passengers to have an alternative to the in-flight phone service such as GTE's Airfone.^{[citation needed]} Andy Plews a spokesman for UAL's United Airlines was quoted as saying "We don't believe it's a good safety issue"..."We'd like people to use the air phones." Such services are much more expensive than mobile phone services and provide slow data rates at a similarly high price.^{[citation needed]} In general the airlines have had little success in selling these services and the in-flight phone equipment has disappeared from most U.S. domestic flights.^{[citation needed]}

Current status

In flight technology

Some airlines have installed technologies to allow phones to be connected within the airplane as it flies. Such systems were tested on scheduled flights from 2006 and in 2008 several airlines started to allow in-flight use of mobile phones. Some airlines that are installing the equipment are also considering the issue of "phone-free zones" and "quiet time" on long flights.^{[citation needed]}

Status of specific regions and individual airlines

Emirates Airline

On 20 March 2008, Emirates Airline flights began allowing in-flight voice calls on some commercial airline flights.

European services

AeroMobile and OnAir allow the use of personal electronics devices aboard flights. The services are most readily available in Europe and are licensed to specific airlines.

Qantas

As of mid April 2007 Qantas teamed up with Panasonic Avionics Corporation and AeroMobile to commence a three-month trial that would "enable customers to send and receive e-mails, access the Internet and send and receive text messages from their own mobile phone".

Ryanair

On 30 August 2006 the Irish airline Ryanair announced that it would introduce a facility to allow passengers to use their mobile phones in-flight. This service started on 19 February 2009 with 20 of their Dublin based aircraft.

Turkish Airlines

Turkish Airlines' stated position is that "Mobile phones interfere with the flight instruments and have a negative effect on flight safety."

Mobile phones on corporate jets

Dassault Aviation implemented a new concept designated SafeCell on 2 April 2009 when the Falcon 2000 commenced flying.

United Kingdom

On 18 October 2007 the Office of Communications published proposals for the technical and authorisational approach that would be adopted to allow this for European GSM users on the 1800MHz band on UK registered aircraft. and on 26 March 2008 Ofcom approved the use of mobile phone-supporting picocells aboard aircraft in the United Kingdom. Airline companies will have to first equip the aircraft with picocells and apply for licences.

Regulations and practice in the United States

To prevent disruption to the cellular phone network from the effects of fast-moving cell phones at altitude (see Technical discussion, below), the FCC has banned the use of mobile phones on all aircraft in flight. The FCC did, however, allocate spectra in the 450 MHz and 800 MHz frequency bands for use by equipment designed and tested as "safe for air-to-ground service" and these systems use far more widely separated ground stations than standard cellular systems. In the 450 MHz band co-channel assignments are at least 497 miles apart and in the 800 MHz band only specific sites were authorized by the FCC. The 450 MHz service is limited to "general aviation" users, usually corporate jets, while the 800 MHz spectrum can be used by airliners as well as for general aviation. The 450 MHz spectrum is named AGRAS while the name of the 800 MHz service is under review following an auction of the spectrum in 2006.^{[citation needed]}

The FAA in 14 C.F.R § 91.21 prohibits the use of portable electronic devices, including mobile phones, for all commercial flights and for those private flights being made under instrument flight rules (IFR). It does allow that the airline (or, for privately operated aircraft, the pilot) can make an exception to this rule if the operator deems that device safe. This effectively gives the airline, or the private pilot, the final word as to what devices may safely be used aboard an aircraft as far as the FAA is concerned although the FCC restriction still applies.

• Note that for aircraft operated by an airline the pilot is not considered the "operator" and cannot legally allow exceptions to the airline's restrictions although the pilot may dictate additional restrictions.

Future technologies

A few U.S. airlines have announced plans to install new technology on aircraft which would allow mobile phones to be used on aircraft, pending approval by the FCC and the FAA. This method is similar to that used in some cars on the German ICE train. The aircraft would carry a device known as a picocell. A picocell acts as a miniature base station (like a cellphone tower) communicating with cellphones within the aircraft and relaying the signals to either satellites or a terrestrial-based system. The picocell will be designed and maintained for full compatibility with the aircraft avionics. Communication between the picocell and the rest of the telephone network will be on separate frequencies that do not interfere with either the cellular system or the aircraft's avionics, similarly to the on–board proprietary 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 metal shell both the picocell's and the cell phones' output power could be reduced to very low levels, which would reduce the risk of interference. Such systems have been tested on a few flights within the United States under a waiver from the FCC.^{[citation needed]}

ARINC and Telenor have formed a joint venture company to offer such a service aboard commercial aircraft. The cell phone calls are routed via satellite to the ground network and an on-board EMI screening system prevents the cell phones from attempting to contact ground-based networks.

These systems are comparatively easy to implement for customers in most of the world where GSM phones operating on one of just two bands are the norm. The multitude of incompatible mobile phone systems in the United States and some other countries makes the situation more difficult — it is not clear if the onboard repeaters will be compatible with all of the different cell-phone protocols (TDMA, GSM, CDMA, iDen) and their respective providers.

Technical discussion

The U.S. Federal Communications Commission (FCC) currently prohibits the use of mobile phones aboard any aircraft in flight. The reason given is that cell phone systems depend on channel reuse and operating a phone at altitude may violate the fundamental assumptions that allow channel reuse to work.

Cell phones are intentionally designed with a low power output. A tower is the center of a "cell" and due to attenuation with distance (inverse square law) cell phone transmissions at ground level can usually be received only weakly by towers in adjacent cells and not at all in cells farther away (non-adjacent cells). This allows the channel used by any given phone to be reused by other phones in non-adjacent cells. This principle allows tens or hundreds of thousands of people to use their phones at the same time in a given metropolitan area while using only a limited number of channels.

Channel reuse works because a cell phone on the ground will only have one "closest" tower that can possibly use a particular group of frequencies, CDMA codes, or time slots. The software that manages the system assumes that the signal from a phone on a particular tower can, on other towers, only be "heard" at greatly reduced signal strength. The frequency, code, or time slot used by the phone can therefore be reused by other phones on other towers.

If a cell phone is operated from an aircraft in flight above a city these assumptions are no longer valid because the towers of numerous different cells may be about equidistant from the phone. Several towers might well assume that the phone is under their control and the phone could be assigned a free channel by one tower but could also be heard on other towers using the same channel group. The channel might already be in use on those other towers and could cause interference with existing calls. Even if the software can cope with hearing the same phone on multiple non-adjacent towers the result at best is an overall decrease in system capacity.

An additional concern is the output power of the cellular handset. Because the towers might be miles below the aircraft the cell phone might have to transmit at its maximum power to be received. This would increase the risk of interference with electronic equipment on the aircraft.

See also

• Air-ground radiotelephone service
• Ansett New Zealand Flight 703 – There is speculation that mobile phone interference with the radio altimeter while on instrument approach may have caused this crash although the official accident report cites the cause as pilot error and states "The aircraft manufacturer’s avionics representative advised that there was no likelihood that the operation of a computer, other electronic device or a mobile phone would have affected the aircraft’s flight instruments."
• Crossair Flight 498 – An alternate theory of the 2000 crash of this flight was based on the use of passenger mobile phones which resulted in a number of countries outlawing the use of cell phones on flights.

Notes

• Study: In-flight cell calls pose risk to planes
• 'Hello? I'm on the plane': Ryanair passengers will be able to use mobiles on board – at a price
• 47 CFR § 22.925: FCC prohibition of airborne cell phone use, 1Oct2006

External links

• 14 CFR § 91.21: The FAA rules regarding portable electronic devices
• Advisory Circular 91.21-1A: Use of portable electronic devices