A cost-benefit case for ADS-B equipage of general aviation aircraft cannot be made, concluded an Aviation Rulemaking Committee (ARC) in a report published last week. Analysis of public comments relating to the FAA’s September 2007 ADS-B NPRM showed 101 positive and 1,271 “non-positive” responses. Sources tell AIN that most commenters regarded the plan as offering little or no benefit compared with its compliance costs. The FAA subsequently appointed the ARC to recommend improvements to the document. The NPRM mandated ADS-B “Out” units in all aircraft by 2020, but these provide pilots with no more than their current transponders, which remain required as ADS-B backups. The more expensive ADS-B “In” equipment, whose cockpit displays show other aircraft, was not mandated. But sources say that without incentives, many operators might delay buying ADS-B “Out” equipment, assuming that, like GPS units and personal computers, avionics prices will fall over the next 12 years while units purchased today could be obsolete by 2020. As one FAA insider conceded to AIN, “We didn’t anticipate it might be interpreted that way.”