In January of 1993, a pilot found that his directional gyros were off by as much as thirty degrees. A flight attendant searched the passenger compartment, and found twenty-five AM/FM radios tuned to the same football game and a laptop computer in use. Once the devices were shut off, under threat of confiscation, the navigational controls returned to normal. In another instance, an airplane received a report that it was seven miles off course. A stewardess checked the cabin and found a laptop computer with an external battery pack, a video game, and a calculator in use. Once shut off, the primary compass returned to normal. Another aircraft experienced trouble with its communications radio and asked for the flight controllers to switch to a different frequency. The crew switched over, heard music on the new frequency, and switched again with the same result. A flight attendant asked the passengers to shut off their FM radios, and the cockpit regained normal communications. Time reported that a landing DC-10 "almost crashed when a passenger in first class turned on his portable compact disc player." These incidents have created a state of terror in the airline industry. To the airlines, computer-carrying actuaries are as dangerous as bomb-carrying PLO terrorists. According to airlines, the radio frequency (RF) waves created by all electrical devices can interfere with sensitive equipment used to monitor certain RF waves to help navigation. If passenger's PEDs, or Portable Electronic Devices, interfere at these frequencies with enough strength, the devices could damage or disable an airplane's navigational controls. Currently, all major airlines ban the use of PEDs during landing and takeoff. The policies during noncritical flight times vary: many, including Delta, Northwest, and SwissAir, do not allow laptop peripherals, CD players, FM radios or TVs at all. However, many experts do not agree about the risk. Boeing, the world's largest aircraft manufacturer, has conducted its own tests to determine the risk. Jim Boone, the director of avionic/flight systems for Boeing, states, "There is no problem." Instead of ignoring the problem or banning PEDs and hoping nothing else happens, airlines need to act. Airlines need to conduct intense real-world tests to determine what devices cause interference and take proper precautions for those devices by shielding the navigational antenna in order to guarantee passenger safety.
In October of 1993, PC/Computing conducted experiments to determine what devices actually cause strong interference in the proper frequencies. The VORs (very high frequency omnidirectional radios) that airplanes use operate between 108MHz and 117.95MHz, just above FM radio frequencies. Of the seven laptops tested, only two emitted any interference. However, since the signal was barely over the normal noise level, the RF waves would not cause any damage. When tested three meters from the receiver antenna (in a Boeing 727, passengers seated at the very back of the cabin are about 12 meters from the navigational antennas), the strongest signal was -105 dBm. To interfere, a signal of -62 dBm is needed, which is approximately 60,000 times stronger than -105 dBm. CD players produced some RF waves, but the frequencies were not in the right range. Peripherals also displayed little interference. On the other hand, AM/FM radios produced strong signals in the correct frequencies, especially when multiple radios were tuned to the same frequency, as was the case mentioned with the football game. Cellular phones (which are not allowed to be used at any time on any airline) produced the strongest signals in the correct frequency. If the airlines conducted these tests, they would probably reach similar conclusions. Only AM/FM radios and cellular phones need to be banned. Business passengers would flock to an airline that allowed laptops to be used at all times and could prove that laptop use is safe.
By shielding the back of the airplane to prevent cabin emissions from reaching the navigational receiver antenna, airlines can provide an even safer environment for their passengers. Hearing aids and pacemakers obviously cannot be banned, even though they produce significant RF waves. If laptops or other devices are old or cracked, internal signals can radiate out. Simple aluminum shielding would be sufficient to block most of the RF waves. However, by using technology developed in the new generation of "fly-by-wire" aircrafts, such as the Airbus A-320, airlines can replace mechanical and hydraulic linkages with digital ones. Not only are these linkages more accurate and dependable, they can withstand a high-intensity radiated field, as mandated by the FAA. This would prevent terrorists from utilizing a remote controlled unit capable of giving off large doses of VOR range emissions. Navigational control and communications would both be affected. The threat of removing all navigational control and outside communication is as dangerous as any bomb. Pilots would have to control the aircraft by what they could see out the window and by the feel of the plane. Airlines with the new type of "fly-by-wire" or shielded compartments would become the leaders in safety in the flying industry.
Although intensive testing and shielding would cost a great deal, passenger safety is worth any cost. In 1988, the Radio Technical Commission for Aeronautics (RTCA) conducted tests to determine whether interference could potentially threaten air safety. They concluded that only an unlikely combination of events could cause any problems. However, the RTCA recommended that the FCC and the FAA research the problem further. In five years, neither have done anything. But recently, the FAA has asked the RTCA to reopen its investigation. A special committee with members such as Apple, IBM, Sony, and PC/Computing has been established to study RF emission. The airlines need to cooperate with this committee in order to provide maximum protection for their passengers. The tests should be complete by the end of this year. By using these findings and new shielding technology, airlines should one again make flying one of the safest methods of transportation.
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