Is It Safe to Use Your Laptop in the Air?

The departure lounge in any airport terminal tells the story. Dozens of men and women in suits are clasping cellular phones between ears and shoulders, peering at beepers, scanning electronic calendars and tapping on laptop keyboards.

This is personal electronics at its most powerful. But there’s just one problem: Some airline safety experts believe the accouterments of the wired, as well as entertainment devices such as CD players and game machines, are jeopardizing air safety by interfering with navigation equipment.

Already, most airlines have banned the use of electronic devices during takeoffs and landings. But questions are still being asked about whether additional restrictions, possibly including a total ban on in-flight electronics use and inspections to ensure compliance, might be necessary.

There is little consensus as to whether a safety problem exists. Airlines, eager to keep their best customers happy, say the current restrictions are adequate, and the Federal Aviation Administration so far agrees. Some business travelers are impatient with even the current restrictions.

“My question is about the probability of such problems occurring,” says Christopher McGratty, chairman of McCammon McGratty & Co. of Dallas. “If the probability is quantifiable, then I think people would be happy to forgo the convenience of using their equipment. But because I’ve never heard a credible explanation, the blackout periods annoy me.”

There are still many unknowns about the possible in-flight effects of electromagnetic emissions, or radio signals, from portable electronic devices.

PEDs operate at frequencies from a few kilohertz for simple radios to 133 megahertz for laptop computers. When signals are generated simultaneously, as they often are by dozens of passengers operating a variety of PEDs, the emitted frequencies can cover the entire range of navigational and communication frequencies used aboard an aircraft.

Most airplane computer systems are shielded from radio frequency interference. Navigational and communication systems, however, are difficult to shield because they operate within those frequency ranges and have antennas located at various points outside of an aircraft’s skin.

“That is the primary focus of the PED issue,” said David Walen, national resource specialist for electromagnetic interference at the FAA. “The concern is that electronic devices will radiate at a particular frequency that may be received by a navigational antenna--and, in turn, that the receiver attached to the antenna will think it is receiving a valid signal when it isn’t. The fear is that it will try to interpret that unintentional signal rather than the real signal from the ground.”

Until recently, the evidence of actual interference has been anecdotal. Interference is difficult to duplicate in a controlled testing situation because there are so many variables: different types of portable electronic devices, often altered either for improvement or simply by wear and age; different types of equipment on the plane; and different airframe structures.

Even the placement of the electronic device on the plane has an effect because electromagnetic frequencies will be absorbed by some things and reflected by others.

“It’s like the rabbit ears we used to use to improve television reception,” said Finbarr O’Connor, electromagnetic compatibility manager of R&B; Enterprises in West Conshohocken, Pa. “You could get great reception if you held on to one of those ears with one hand and stood on one leg, just so.”

The two organizations that have studied the issue the most thoroughly are the National Aeronautics and Space Administration’s Aviation Safety Reporting System (ASRS) and the RTCA, formerly known as the Radio Technical Commission for Aeronautics.

The ASRS has maintained a database of voluntarily reported safety incidents for the last decade. Of the nearly 69,000 overall incidents, 52 were thought to have involved interference from PEDs. Because reports made to ASRS are voluntary, officials there say they cannot be used to establish the scope of the problem.

But the reports do provide dramatic illustrations of problems when they occur. In one incident, a large passenger plane was at cruising altitude, 28,000 feet over the Midwest, when the needle on its main navigational compass began to swing erratically.

A quick check of the navigational equipment by the pilots yielded no explanation. Everything appeared to be working normally. Then a flight attendant checked the cabin and discovered a passenger playing an electronic chess game. The instant the hand-held game was turned off, the compass readings returned to normal and the plane was able to continue its flight safely, according to the report.

Reports by pilots of similar incidents have spurred concern, although no accident is known to have been caused by a portable electronic device.

“We have identified incidents that have had various effects on navigation or communications equipment, but none have jeopardized the safety of the flight,” said Vince Mellone, operations manager for the ASRS. “Since the airlines have adopted the policy of not allowing the devices while planes are descending or ascending, there has been a big drop-off in the number of incidents reported.”

But some pilots disagree, arguing that the current prohibition during takeoffs and landings doesn’t go far enough.

“The ban is incorrect in the assumption that 10,000 feet is the altitude limit on these occurrences,” said one pilot quoted in the ASRS database who said he experienced interference on his flight at about 25,000 feet.

“Monitoring passengers for the use of these items is virtually impossible,” said another pilot, after repeated warnings over the plane’s public announcement system failed to convince passengers to turn off their radios and computers.

The only solution, according to some pilots, is to insist that computers and similar devices remain turned off throughout the flight.

“Until corrective measures are taken by industry and government to rectify potential hazards caused by electronic interference, airlines should give consideration to having portable electronic devices shut off,” said one commercial pilot.

But the airline industry contends that the risks of interference from electronic devices are minimal and that further restrictions are not warranted based on current knowledge.

“The Federal Aviation Administration’s current position is that above 10,000 feet, while there is a finite risk, it is small and acceptable,” said John Wade, marketing manager for commercial aerospace at Primex Aerospace Co. in Redmond, Wash. “There is also a risk that all engines will simultaneously stop, but we fly with that risk every day.”

Primex manufactures Empower, an in-seat laptop supply source that many airlines are now installing, and Wade worries that “laptops are simply becoming a scapegoat for many other problems.”

Wade said electronics manufacturers could improve the shielding for computers and other electronic devices so they cannot interfere with navigational equipment.

Representatives of some pilot groups, however, think the responsibility lies with the airlines and the regulators. They contend that passengers should be educated better about the dangers of using computers and games on aircraft.

Others, including the RTCA, advocate installing emission-detection devices, similar to smoke detectors, aboard commercial aircraft. Unfortunately, such devices are in the development stage, and neither the FAA nor the RTCA would say when they will be available for use. O’Connor, the electromagnetic expert at R&B; Enterprises and a member of the RTCA’s study committee, said the potential for interference exists but that additional studies are necessary to determine the precise danger.

“The potential for this kind of interference is high, but what is the probability?” asked O’Connor. “Is it a nuisance or a safety issue? We simply don’t know yet. There is a lot of work that needs to be done.”