Soon-to-be-Released Technical Report Could Permit Cell Phones to Fly

The 400-word Radio Technical Commission for Aeronautics report does not advocate the use of cell phones on planes, but rather details what tests airlines should conduct to determine whether a plane is at risk of interference.

The RTCA's reports ultimately could lead to the FAA's allowing in-flight cell phone use. Still, an airline would have to show the agency that each make and model of aircraft is safe from interference, said Gregor said.

"Proving noninterference could be a big challenge for airlines," he said.

The FAA allows certain electronic devices -- laptop computers, handheld video game devices, MP3 players and even cell phones whose wireless capabilities are off -- to be used after a plane reaches an altitude of 10,000 feet and if an airline has proved that the device does not interfere with safe operation of the aircraft. The agency said that at lower altitudes, any interference could be more of a safety hazard as the crew focuses on takeoffs and landings.

The FAA said a cell phone signal differs from other portable electronic emissions because it is strong enough to be received at distances far from the user. While cell phones and other portable electronics do not operate on the same frequencies as an airplane's communications equipment, they can emit unintentional signals.

"The issue tends to be what were called spurious emissions," Carson said. "They're not intentional. They're artifacts of the way the radio creates a signal."

Potential dangers:

* The emissions can travel through the plane's windows to make contact with the communication and navigation antennas, mounted on the outside of the aircraft.

* Stray signals can radiate energy that gets into the plane's wiring and travels to its communications receiver or onboard computers to connect indirectly.

* The unintentional emissions can radiate energy that directly makes contact with the onboard computers or communications receiver.

The question is whether those emissions affect a plane's systems, making it unsafe to fly. There is no real proof that they do. Aviation experts have long believed at least one or two passengers aboard every commercial flight inadvertently leave cell phones on, yet cell phones have not been proved to have led to any crashes.

Airlines shared with the RTCA committee a number of anecdotal reports of interference, but the interference could not be repeated in controlled tests, Carson said.

Lufthansa, for example, shared its experiences with the committee in trying to verify reports of interference from portable electronic devices.

"They'd say that `a Game Boy or cell phone was turned on, and when we turned it off, the interference seemed to go away,' " Carson said. "In almost all cases when they chased down those reports, either the interference could not be repeated or they found something else that was the cause of the problem.

"The bottom line is that you need an assessment to determine how the interference is getting in. It's a bad idea to just blame portable electronic devices."

Paul Guckian, vice president of engineering for Qualcomm and a member of the RTCA committee, said the committee's research has shown that cell phones are not the sole issue.

"The fact is that a cell phone or notebook computer or PlayStation Portable -- any of those electronic devices -- have the equivalent potential to interfere with the aircraft communication system," Guckian said.

Boeing and other commercial manufacturers are already taking steps to shield an aircraft's equipment from unintentional emissions, which should make the next generation of planes less susceptible to the stray signals from cell phones and other handheld devices.

Even if the issues with stray emissions are resolved, the FCC is concerned that signals from airplanes confuse cellular networks.

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