Electronic Interference Part 1 – Cell Phones

There are dozens of documented reports that suggest electronic interference from cell phones caused a disruption to key flight instruments, but not everyone is convinced. In some reports, the cell phone wasn’t even “on,” but operation in standby was suspected of causing problems with flight instruments! Other reports contend that there is a lack of direct evidence. Regardless, if you believe “where there’s smoke, there’s fire” then flying with a cell phone should be done with great care — and you’d be in good company.

Boeing research indicates that the fuselage of a standard, aluminum-skinned airplane is a nearly perfect reflector. Cell phone use in that fuselage will result in a great deal of the cell phone’s output being reflected through the aircraft’s interior and if the right harmonic finds the right spot in the avionics, problems will develop. As a result, Boeing has issued formal recommendations that certain electronic devices be turned off during critical phases of flight, and others — including cell phones — not be used at all.

The FAA responded as early as 1989 with FAR 91.21 prohibiting the use of nearly all electronic devices on aircraft. However, the FAA revised FAR 91.21 by 1993 to provide commercial carriers with the right to decide which devices would be allowed and today, both the FAA and independent experts seem unconvinced that there is any real threat.

Try It — At Your Own Risk
Next time you are sitting at your computer, reading iPilot, try this simple test: Place your cell phone within a foot of your monitor, and call it. The electromagnetic waves from many cell phones will scramble the display on the computer monitor. Now think about this in the context of your next flight — you forget to turn off your cell phone and someone calls you. Whether they scrambled the screen or not, those same electromagnetic waves will go bouncing around your cockpit, your flight instruments and your avionics! Translation: Keep your cell phone powered down while you are in flight, and you will avoid any of the electronic interference it can cause.

BOTTOM LINE: FAR 91.21 is clear on this subject, as are the various FCC regulations — Do not use your cell phone in flight unless all other communication has been lost.


A commercial airliner was on a return flight to Dallas / Fort Worth Airport in Texas. After departure, the flight crew was directed by New York Departure Control to proceed directly to Parke Intersection. Before reaching Parke, New York Departure directed the airliner to turn left 10 degrees and intercept the LRP 067 radial and proceed inbound. Upon intercepting the radial and passing 13,000 feet, New York Departure advised the flight crew that they were south of the course.

The flight crew started to look over the flight instruments, and found that they were all indicating that they were on the 067 radial. The flight crew asked the flight attendant to check the cabin for the usage of illegal electronic devices. While this check was in progress, the crew found both compass systems 40 degrees in error with the wet compass!

The flight attendant found two Game Boys in use, and one cell phone. The flight crew requested that the cell phone be shut down, and reset the compass systems. Once this action was performed, the problem was corrected and the flight continued.

The flight crew considered this problem as a Navigation Compass System Error caused by Passenger Electronic Devices in use. This is just one of dozens of similar case files in the NTSB archives, concerning the use and interference of cell phones while in flight.

Editor’s note: For a list of ASRS incidents involving electronic interference, visit http://asrs.arc.nasa.gov/report_sets/ped.pdf and for more information on the subject, watch for George’s next installment…