The Federal Aviation Administration this week asked for public comment on passenger use of portable electronic devices on board aircraft. This could lead to a relaxation of current rules, which now only allow use of portable voice recorders, hearing aids, heart pacemakers, and electric shavers. An exemption allows use of any other personal electronic device (PED) that the aircraft operator has determined will not cause interference with the navigation or communication systems on the aircraft.
It’s too early to say what changes will be made to existing rules, but it may help make airline rules more consistent. For example, Southwest Airlines allows in-flight passenger use of GPS on its 737 aircraft, while Delta Airlines does not.
One of the most interesting parts of the FAA release is the Supplementary Information section where the history of the regulation of PEDs on aircraft is outlined and the potential impact analyzed.
The FAA's first rulemaking to address the issue of PEDs on aircraft was published in 1966. A major issue then was local oscillator radiation from portable FM radios. FM radios receive frequencies in the range 88-108 MHz and most FM receivers operated with an intermediate frequency (IF) of 10.7 MHz. The local oscillator required to convert the incoming RF to the IF frequency therefore radiates a signal from 98.7-118.7 MHz. Because the VOR system used for aircraft navigation operates in the 108-118 MHz band, it’s easy to see why the FAA was concerned about interference.
An analysis of potential PED interference on aircraft today is more difficult. Any device with a microprocessor requires a clock generator. Depending on the processor and the application, signals from these clock generators could fall anywhere in the RF spectrum, extending well above 1 GHz with current notebook and tablet designs. RF emissions from digital devices is strictly limited by FCC Part 15 rules, but many devices now include wireless broadband, Bluetooth, Wi-Fi and other intentional transmitters operating in several frequency bands. While these emissions are unlikely to cause any problems in their own bands, a damaged device could radiate signals that could interfere with critical RF systems such as GPS navigation.
The FAA inquiry raises some interesting issues beyond RF. It asks, “If some PEDs are found to be compatible with aircraft systems, should there be restrictions on the use of PEDs for other reasons?”
One example is the use of cell phones, which many passengers oppose in a tightly packed aircraft cabin. (I didn't see mention of the potential for interference to cell phone base stations on the ground.)
Another concern is that the devices themselves, not their RF radiation, could be a problem if the plane encounters turbulence and the devices become projectiles.
The FAA inquiry asks, “If some PEDs are found to be compatible with aircraft systems, should requirements to stow PEDs for takeoff, approach, land and abnormal conditions exist nonetheless to prevent personal injury?”
I often see passengers on flights leaving tablets and cell phones turned on during the times PED use is not allowed, stashing them in a purse or seat back pocket or just placing them face down on their lap. It’s also not unusual to see cell phones being turned on while the jet is on final approach--a particularly critical period of the flight when the flight attendants are seated. Fortunately the FAA has criteria (AC 20-164) for aircraft manufacturers and modifiers to establish PED-tolerance for new and existing aircraft, but that may not apply in the case of a malfunctioning device.
There is another option for such situations.
The FAA inquiry has a section about “Active monitoring for harmful interference.” Crew members would use this to detect harmful interference from PEDs, and instruct passengers to disable devices when they generate harmful signals. The FAA inquiry asks, “Should the FAA consider working with industry to develop standards for an active PED monitoring system?”
Considering how difficult it can be to change human behavior, I wasn't surprised to see the FAA inquiry also asking “Is it necessary to establish aircraft certification regulations to require new aircraft to be PED-tolerant?”
These are just a sample of the issues and questions raised in the FAA inquiry. Information in response to this inquiry must be submitted 60 days after the FAA inquiry is published in the Federal Register.