In 2006, the FAA proposed requiring that many communications users seek FAA No Hazard Determinations not only before they make changes in the height of a tower, but also prior to frequency or power changes. The FAA sought to review applications to determine if proposals would create any interference to frequencies used by the by aircraft and by the FAA for air navigation purposes. This review would be in addition to any review that the FCC made of interference considerations. Many communications companies and engineering firms argued that this second layer of frequency review was unnecessary; and certain engineering groups contended that the FAA’s interference programs were not accurate – finding interference where none existed. After over 4 years of consideration,the FAA has now decided that most of the frequency blocks that it was considering did not really pose a threat to air navigation, with one exception. The FAA determined that interference problems do arise from FM operations, and thus the FAA did not dismiss their proposal to require its approval of FM changes – even where no tower height changes are planned.
The FAA, however, apparently will not be making this decision alone. Instead, that FAA is coordinating with the FCC and NTIA (an Administration in the Commerce Department that coordinates between various government agencies that use spectrum) to adopt policies that will govern the potential for interference from FM stations to FAA operations. The FAA’s Notice says that more information about what is to be proposed for FM stations should be forthcoming soon. This can be a real issue for FM stations, especially ones proposing significant power increases or frequency changes in congested metropolitan areas with numerous public, private and military airfields in the vicinity.
There have been a number of cases where FM stations have received FCC construction permits only to run into construction issues based not on concerns over tower heights, but instead based on FAA interference concerns. In a few cases, these issues have arisen after an FM station has commenced operations, causing broadcasters to have to turn their stations off after they had become operational. The FCC’s rules currently do not require FAA approval for a power or frequency change, except when the change involves a change in tower height. Even the FAA rules do not spell out this concept of seeking prior approval for any proposal that could cause RF interference to FAA air navigation frequencies. Nevertheless, in recent years, the FAA has conditioned new tower construction on tower owners coming back to the FAA to get approval for the addition of new frequencies on their towers, even if the tower height is not changed. As the tower owners subject to such conditions on their tower operations are sometimes slow to seek FAA approval (waiting for a signed lease, for instance), FAA issues often do not come to light until late in the FM station’s construction project – often well after FCC approval of their construction permits, and often after the construction has begun following the signing of a lease agreement. And, as stated above, many engineers feel that the current standards used by the FAA far overstate the potential for interference to FAA operations from FM stations. While no one wants to cut it too close when air safety is on the line, many engineers have concluded that the FAA program will block station construction even when the predicted interference is at heights where aircraft don’t fly (like where it is close to the ground) or on frequencies that already receive significant interference from existing FM stations (so that any new interference would be effectively masked by the existing interference). These issues need to be considered, as the potential for significant restrictions on FM changes may well arise from an across the board approval process using very tight interference standards. This is a very important proceeding. So keep watching to see what happens in coming months.