In the last blog, we discussed how the FAA and aircraft industry recognized that personal electronic devices, or PEDs, were causing problems aboard aircraft. With the proliferation of PEDs onboard, and especially those with wireless capabilities, action was needed quickly to address safety concerns. The FAA requested the RTCA form a new committee, SC-202, made up of over 100 individuals from the aircraft industry, airlines, computer, medical, telecommunication, and commercial electronics industries, consultants, FAA, and elected officials. The group was formed specifically to address PEDs that had transmitters, cellular technology, wireless radio frequency networks, and the like. These transmitting PEDs are referred to as T-PEDs.
There was a recognition that guidance for the use of T-PEDs was extremely important. Incidents were being reported, often anecdotal and erroneous or misinterpreted. However, it created much interest in the media and the public. Several issues with PEDs were found, including:
- They were not configured the same, or maintained, and thus could be degraded;
- They could be located anywhere in the passenger deck, including (and often) in the flight deck;
- T-PEDs could be activated, deactivated, carried on the person, stowed in luggage, or in a number of other variabilities;
- T-PEDs had less stringent standards applied than aircraft-installed equipment. This resulted in a collision between T-PEDs operating bands and aircraft radio bands.
SC-202 recognized that there was not a well-established understanding of the degree to which aircraft were tolerant of T-PEDs or the importance of each phase of operation (departure and arrival, cruise, taxi, or parked). The issue had to be quickly addressed, which induced performance of tests of the T-PEDs, analysis of the aircraft to be immune, and understanding that would be a monumental task on many aircraft, then to perform testing to determine potential issues. Front-door coupling (direct exposure to the aircraft antenna) and back-door coupling (exposure to the cabling or directly into the equipment) were addressed.
The technology of many aeronautical signals at the time was of 1940s vintage, including VOR, Glideslope, and Localizers used for landing. These did not include advanced signal processing to mitigate interference signals from PEDs or T-PEDs. Receivers that were exposed to out-of-band interference from T-PEDs could become desensitized, losing operational dynamic range. Intermodulation products, cross modulation, spurious emissions, and many other problems were considered. After four revisions were generated in four years, the 2008 edition of DO-294C, Guidance on Allowing Transmitting Portable Electronic Devices (PED) Tolerance, is 412 pages long and provides recommendations on how to deal with these issues.
Understanding this was not adequate, SC-202 also created DO-307, Aircraft Design and Certification for Portable Electronic Devices (PED) Tolerance. Work was continued by SC-234, which updated the document to DO-307B in 2022. Along with the 2016 document DO-363, Guidance for the Development of Portable Electronic Devices (PED) Tolerance for Civil Aircraft, they provide airframe manufacturers and airlines with methods to determine safety margins and criteria for risk assessment and the ability to analyze, troubleshoot, and mitigate issues that may be found.
Much of the instrumentation testing is based on DO-160D and later. In general, to assure tolerance to T-PEDs, Category R is often the minimum level required for Section 20. Category R has two advantages. First, radiated susceptibility is stepped from 20 V/m below 400 MHz to 150 V/m above, where many of the T-PEDs transmitters operate. It also uses 0.1%-4% pulse modulation instead of squarewave amplitude modulation or 50% duty cycle pulse modulation. This short duration modulation is more in line with the type of transmissions encountered from T-PEDs. In comparison, Category W of 100 V/m starts at 100 MHz and is performed both CW and with 50% squarewave modulation. For many avionics, despite being a lower level above 400 MHz, Category W is a more difficult requirement to meet.
