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British Civil Aviation Authority declares: mobile phones interfere with avionics

Posted on 3-May-2003 13:50 | Filed under: News

Research by the Civil Aviation Authority (CAA) has proved that mobile telephone transmissions made by airline passengers can interfere with aircraft equipment.

The tests support the existing CAA ban on the use of mobile telephones on board aircraft when the engines have started. This has been in effect since the widespread introduction of mobile telephones and was supported by initial research performed in February 2000.

The latest study found that the use of mobile telephones can adversely affect navigation and communication functions, producing significant errors on instrument displays and background noise on audio outputs.

The research backs up reports from pilots, who have stated that interference from mobiles has caused:

  • False notification of unsafe conditions, e.g. incorrect baggage compartment smoke alarm warnings
  • Malfunction of aircraft systems
  • Interrupted communications due to noise in the flight crew headphones
  • Distraction of crews from their normal duties due to increased work levels and the possibility of having to invoke emergency drills

    Dan Hawkes, the avionics specialist at the CAA who supervised the research, explained: �The tests demonstrate that mobile telephone use near an aircraft�s flight deck or avionics equipment bay can adversely affect systems that are essential for safe flight.

    �For safety reasons the current policy of prohibiting the use of mobile telephones by passengers while the aircraft�s doors are closed for flight must continue.�

    The report also contains a number of follow-up recommendations:

  • Continued restriction of mobile telephone use by passengers in aircraft
  • Aircraft operators should alert their flight crews to the specific risks from mobile telephone use on the flight deck, and introduce procedures to ensure telephones are switched off. Similarly, the general aviation community should be alerted to these dangers in small aircraft
  • Check-in staff should seek confirmation from passengers that mobile telephones in luggage have been switched off
  • Reminder notices should be placed in airport departure lounges and at aircraft boarding points
  • Research into mobile telephone interference risk should be continued to take account of continuing technological advancements

    In October 2002, a set of avionic equipment was tested under controlled conditions in a test chamber for susceptibility to cellphone interference. General aviation avionic equipment, representative of earlier analogue and digital technologies, was used. The equipment, comprising a VHF communication transceiver, a VOR/ILS navigation receiver and associated indicators, together with a gyro-stabilised remote reading compass system, was assembled to create an integrated system.

    The tests covered the cellphone transmission frequencies of 412 (Tetra), 940 (GSM) and 1719MHz, including simultaneous exposure to 940 and 1719MHz. The applied interference field strengths were up to 50 volts/metre for a single frequency, and 35 volts/metre for dual frequencies.

    The following anomalies were seen at interference levels above 30 volts/metre, a level that can be produced by a cellphone operating at maximum power and located 30cms from the victim equipment or its wiring harness.

  • Compass froze or overshot actual magnetic bearing.
  • Instability of indicators.
  • Digital VOR navigation bearing display errors up to 5 degrees.
  • VOR navigation To/From indicator reversal.
  • VOR and ILS course deviation indicator errors with and without a failure flag.
  • Reduced sensitivity of the ILS Localiser receiver.
  • Background noise on audio outputs.

    Most anomalies were observed at 1719MHz.

    The results of the tests endorse current policy that restricts the use of cellphones in aircraft. Recommendations are made that would further reduce interference risks, and to continue the studies to determine interference effects in aircraft from cellphones and other transmitting devices.

    The download link below points to the .pdf with the full report.

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