The Civil Aviation Authority research found that standard cell phone use can cause a compass to freeze or to overshoot its actual magnetic bearing. Also, flight deck and navigation equipment indicators can be rendered unstable and inaccurate, and transmissions can interfere with critical audio outputs.
Cell phone use has long been banned on airplanes, along with use of many other electrical devices. But passengers have often accused airlines of being over-officious in their enforcement of the ban, even suggesting that it is unnecessary. Many airlines have had experience of passengers who are willing to break the ban in order to make a call. This latest research may frighten passengers into compliance with the rules.
In the United States, the Federal Aviation Administration (FAA) bans the use of cell phones on airplanes because of worries that calls could interfere with a plane's navigation system.
A number of anonymous posters on the Professional Pilots' Rumour Network--a popular online community for airline pilots and crew--expressed mixed feeling over the findings.
One poster said: "Occasionally during the taxi out, we overhear the characteristic rapid chirping of a mobile phone through our headsets. More often than not, it turns out to be a crew phone, we switch it off, then continue with no ill effects.
"Sometimes, however, it becomes necessary to hold clear of the runway and make (an announcement) reminding (passengers) to switch their phones off. At the very least, something back in the cabin is emitting enough of a signal to be picked up by the cockpit intercom. I think that once in a while I have observed deviations in some of the aircraft (navigation) kit while the interference is going on."
Another poster on the site expressed concerns over the issue, suggesting that it is almost impossible to ensure all cell phones are switched off.
"If (the findings are) true, then we can never eliminate the possibility of an active phone on board by simply issuing instructions that all mobiles must be switched off. We either need a foolproof system of scanning for active phones (tricky because they can be 'quiet' for minutes at a time) or we need to 'harden' aircraft systems so this ceases to be a threat."
Silicon.com's Will Sturgeon reported from London.