Portable Electronic Devices

Radio waves originating from either space based or ground stations must be in range of the aircraft transceivers for a connection to be initiated and once completed the traditional monthly bill from the phone company won’t come close to covering the connection costs.

An aircraft cabin is a rather fragile environment and a majority of WiFi routers operating here are reduced wattage from those found in the home or office. This can, in fact, be limited by the airworthiness documentation approving the system.

Many factors can impact the successful use of PEDs in a wireless aircraft. The signal is based on a standard WiFi protocol known as the 802.11 standard and uses 2.4 gigahertz as the operating frequency. Not all WiFi compliant devices have the same sensitivity which means some types of PED demand more of the signal than others to function and can reduce the signal for other consumers. Also, the more users streaming data will cause a slow down of the network as the data stream flow can be compared to a pipe and once capacity is reached the stream backs up.

Bluetooth equipment has been confirmed to raise havoc on 802.11 networks as it shares the 2.4 gigahertz airwaves. As Bluetooth utilizes a different data protocol the signal can confuse the 802.11 system bringing data flow to a crawl or even cause a shutdown of equipment. Crews using remote Bluetooth GPS antennas with an IPad have been suspect in terminating cabin Internet activities.

It may be hard to perceive a microwave oven as a portable electronic device but in some instances they do find their way onto aircraft. Microwave energy can be another killer of WiFi and any installation should be tested to ensure an acceptable coexistence.

Interference and the FCC

Cell phones (and other intentional transmitters) differ from most PEDs in that they send signals strong enough to be received at a far distance. Since 1991, the Federal Communications Commission (FCC) has banned the inflight use of 800 MHz cell phones. This is primarily a result of potential interference with ground networks.

The ban requires that in addition to the FAA testing proving no interference with aircraft systems, an operator would also need to apply for an exemption to the FCC before it could allow cell phone use inflight. Even if the FCC ever rescinds its ban, FAA regulations would still apply, and any installed equipment would be subject to FAA certification. The air carrier would have to show that the use of a particular model phone won’t interfere with the navigation and communications systems of the particular type of aircraft on which it will be used.

Airlines often let passengers use newer-model cell phones in what’s called “airplane mode,” disabling the transmit function. This capability allows users to take advantage of other functions. FAA guidance does permit airline passengers to make cell phone calls once the aircraft has landed.

WiFi and frequency analyzers are readily available and can be found in many forms varying from expensive and complex testers to free applications for an Android. Interference can come from a variety of locations including other PEDS, aircraft wiring, and other electronic components. A sweep of an aircraft cabin using a frequency analyzer is a good first step in preventing issues with portable electronics.

The impact of a PED on an operating aircraft has not as yet been fully explored; but, it is still quite probable some impact will occur sooner or later. This may be due in part to frustration of the PED owner with the challenges of staying connected. I just hope the impact does not result from a throwing arm. AMT

Jim Sparks has been in aviation for 30 years and is a licensed A&P. He is the manager of aviation maintenance for a private company with a fleet including light single engine aircraft, helicopters, and several types of business jets. He can be reached at sparks-jim@sbcglobal.net.