The flight attendant closes the door, and we all turn off our cell phones, right? Wrong. People use cell phones on airlines quite a bit, even when they're not supposed to, a new study shows. Because the signals given off by phones and other electronic devices can interfere with a plane's navigation, the researchers argue that steps should be taken to reduce any potential threats before passengers are allowed to use cell phones routinely on flights.
Avionic equipment has trouble deciphering navigation signals when a crowd of personal electronic gadgets creates background noise. Still, the actual risk to a flight is low, according to Federal Aviation Administration (FAA) simulations on the ground and in laboratories. But no one has monitored what goes on during an actual flight.
So aviation safety researcher Bill Strauss, now at the Naval Air Warfare Center in Patuxent River, Maryland, and colleagues decided to find out. First they scoured the Aviation Safety Reporting System database, which logs about 15% to 20% of safety problems noticed by crews. They found that the U.S. fleet experiences some sort of electronic interference about 2 to 3 times a month. The interference ranges from minor glitches to potentially disastrous anomalies. In 1996, for example, a tower radioed the pilot of a commercial jet, telling him he was 30 degrees off course. The problem disappeared when a passenger turned off his DVD player.
Next, the team decided to take some trips. Boarding 37 commercial flights from three cooperating airlines during 1 month, the researchers placed recording equipment in overhead bins to measure electronic signals emitted in the cabin. Not only did team members see people using their cell phones while flying, the recordings picked up between 1 and 4 signals in the cell phone range per flight. In addition, the team identified signals in the same frequency range as that used by some airlines' GPS navigational equipment. Although the researchers did not evaluate the GPS navigation during flight, the signals coming from the passengers have the potential to cloud the navigation device, says Strauss, especially if 200 people suddenly feel the need to phone home.
"We all kind of knew that people used cell phones on flights, but Strauss has the data," says electromagnetics researcher Jay Ely of the NASA Langley Research Center in Hampton, Virginia. "If [airline] policies become more accepting of these devices, more people will use them, and odds are that will make it more likely we'll see effects." He adds that better coordination between regulatory agencies, policy makers, and device manufacturers will help prevent the use of frequencies that overpower airliner systems.