The road to ADS-B may well be paved with good intentions, but for operators of smaller aircraft there could be some serious ­financial potholes ahead. The FAA’s Engineering Branch announced in August that all future ADS-B installations must be performed under ­individual supplemental type certificates (STC), replacing the earlier ADS-B practice of granting broad field approvals for avionics installations in a variety of similar aircraft models under the agency’s approved model list process.

According to the Aircraft Electronics Association (AEA), which represents the nation’s avionics shops, under the new rule individual ADS-B installation costs will at least double for corporate aircraft, and could increase by as much as 700 percent for general aviation. In a letter to FAA Administrator Randy Babbitt, the AEA stated that the rule “may have an unintended consequence in the industry’s ability to implement your Flight Plan for NextGen.” The association continued, “Without your immediate intervention, this will stall early equipage, delay early implementation and, at the extreme, cause the failure of ADS-B implementation altogether.”

The issue here is that ADS-B GPS position reporting ­accuracy and system integrity ­specifications have been tightened and, since an ADS-B transponder is not a “stand-alone” unit but has to interface with GPS, aircraft altitude and possibly FMS and other systems, the regulators see the STC process as the only way to prove overall system compliance. Ric Peri, AEA v-p for government and industry affairs, pointed out that the ADS-B installation task isn’t as straightforward as it might first appear. It was, he said, “the most complicated ‘simple’ avionics system issue in general aviation.” The FAA does state, however, that as it gains experience in the early use of the STC process, it expects once again to permit (much lower-cost) field approvals.

The interesting question now is just how many private operators will voluntarily step forward to take a large financial hit for their ADS-B installations, to ease the blow for those who follow. In view of the rather doubtful user benefits of ADS-B out, as distinct from the real benefits of ADS-B in, it appears that the AEA’s warning about stalling, delaying and, at the extreme, causing the failure of ADS-B’s implementation could well be prophetic.

The FAA has advised the AEA that it is studying the association’s concerns. Meanwhile, the association has advised its members that it “cannot encourage or support the early implementation of ADS technology until this flawed policy has been resolved.”