It's somewhat disappointing given the number of times this discussion has been had on Pprune that there are some decrying the possibility of passenger electronics interfering with aircraft systems. New comers forgiven.
http://www.caa.co.uk/docs/33/CAP756.PDF
Over the past ten years, the CAA has received 65 MORs relating to interference experienced with one or more of the aircraft systems that cited PEDs as a factor, which were not subsequently found to be caused by a system's malfunction.
PEDs will radiate RF emissions from their internal components such as poorly filtered oscillators, processor clocks, unsuppressed electric motors, and power supply converters. These emissions are referred to as unintentional because they occur as a by-product of the PED's operation.
In addition, some PEDs will also need to transmit RF signals at specified frequencies as a part of their functionality. These transmissions are referred to as intentional transmissions.
PEDs fall into two main categories:
a) those that only emit radio signals as a by-product of their operation (unintentional transmitters); and
b) those that transmit radio signals as a part of their functionality (intentional
transmitters).
Examples of PEDs classified as unintentional transmitters include:
a) personal computing equipment such as laptops, Personal Digital Assistants (PDAs) etc.;
b) electronic cameras;
c) radio receivers;
d) audio and video reproducers;
e) electronic games and toys; and
f) time measuring equipment.
Examples of PEDs classified as intentional transmitters include:
a) mobile phones;
b) personal computing equipment (laptops, PDAs, etc.) with wireless network
devices (plug-ins or embedded);
c) two-way pagers;
d) two-way radios;
e) radio transmitters; and
f) remote control equipment, which may include some toys.
http://www.caa.co.uk/docs/33/CAPAP2003_03.PDF
Effects of Interference from Cellular Telephones on Aircraft Avionic Equipment
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 reports linked interference with effects including:
• False warnings of unsafe conditions (e.g. baggage compartment smoke alarms);
• Distraction of the flight crew from their normal duties;
• Interrupted communications due to noise in the flight crew headphones;
• Increased work load for the flight crew and the possibility of invoking emergency drills;
•
Reduced crew confidence in protection systems which may then be ignored
during a genuine warning;
• Malfunctioning of multiple systems essential to safe flight.
The difficulties experienced in trying to reproduce the events have led many (including pilots) to question whether a genuine problem exists. The degraded navigation precision could result in an inability to meet required navigation performance with potential adverse effects on aircraft separation and terrain clearance. However,
the potential adverse impact on flight safety and the need to keep that risk to tolerable levels have led to restrictions on the use of cellphones in aircraft.
Bolding mine.
Our operation experienced a baggage compartment fire warning put down to a phone in a passengers bag. System itself could not be faulted.
Also remember the stories from a Red Flag (reliably reported) where the F-16 and F-15 were unable to start engines due to, ahem, jamming.