Let me explain why I believe that my statement is accurate.

There are many factors to the problem of mobile phone interference with aircraft systems.

Under normal circumstances, it is recognised that one mobile phone, operating correctly and within its specified limits poses little threat to any aircraft avionic equipment, itself operating correctly and within its specified limits.

However, even with a single phone that is malfunctioning, for whatever reason (ie has been subject to abuse, eg dropped), it can exceed its specified outputs, which in turn COULD affect other equipment.

Similarly if the equipment on the aircraft and its associated wiring has been compromised in any way, it COULD raise the risk of allowing spurious signals to enter and cause problems.

The actual position of the offending mobile within the aircraft cabin is also critical. Certain seats, ie window seats in close proximity to any external aircraft antenna, seats located over the electronics bay (typically located under the floor at the back of first class on a 747) are two such “hotspots” (my word).

Signals within this sealed metal tube (yes, I know the windows and doors can “leak” signals) can “bounce” (my word) around the cabin.

Finally, it has been shown in testing that when a GSM phone is transmitting in close proximity to a transmitting AMPS phone, intermodulation occurs. This results in unwanted frequency components that can affect the DMS system on the aircraft.

Now, if you have a full complement of passengers (typically 400) all using their mobiles;

1) The chances of a faulty mobile on-board is increased,
2) The absolute certainty that passengers will be located in “hotspots” on the aircraft.
3) There will be a cumulative effect of the signals “bouncing around” the cabin.
4) There will be a very high probability that there will be a mix of GSM and AMPS phones in close proximity thereby causing intermodulation.

I am sure that this answer will not satisfy everybody on this forum so I suggest that if you really need to see results from tests, scientifically carried out you can checkout the following site http://ntrs.nasa.gov/search.jsp

Once on the home page enter Doc ID 20030107608. This 198 page document should answer all you outstanding questions.