Nothing unsafe? Don't be so sure...
Effects of Interference from Cellular Telephones on Aircraft Avionic Equipment
"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
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 project was managed by UK CAA and assisted with loaned equipment and personnel from
Vodafone PLC, CSE Aviation (Oxford), and BAE SYSTEMS (Woodford)."
Of the problems above, those that affect ILS (Instrument Landing System) are the ones you really don't want to have while landing in bad weather, only just above the minima...