WAAS approaches are fundamentally different from VOR and ILS approaches in that, because the signal is coming from space, the approach does not rely on the aircraft following a beam transmitted from the ground. WAAS essentially corrects the broadcast GPS signal for errors introduced by atmospheric conditions and other factors. Although the FAAs long-term plan is to decommission VOR and ILS where feasible, that wont happen for more than a decade even under the most optimistic of schedules. So far, of the two WAAS boxes out there, the Garmin AT (formerly UPSAT) CNX80 has an integrated VOR while Chelton Flight Systems uses a GPS/WAAS receiver from FreeFlight Systems to drive its Highway in the Sky EFIS.ĭont scrap your KX-155s yet, though. WAAS receivers, in fact, render obsolete the need to carry a working VOR or ADF for IFR flight. But WAAS does represent a solid step forward in the fundamental shift from ground-based navaids to satellites. If this Jetsons scenario sounds too good to be true, well, it is. The hardware limitations for low approach minima become such things as runway lights and cell phone towers. The FAA and airport operators will be happy because these improvements come with no additional maintenance of ground-based navigation equipment, except for a couple dozen buildings scattered across the country that process information. Dream long enough and youll see datalinked freeflight followed by precision approaches into just about everywhere. Step up your expectations a notch and youll get better instrument approaches into far more airports than is currently possible. GPS is working properly about 95 percent of the time, but WAAS engineers have set the reliability bar at 99.999 percent reliability by the end of 2006. Everyone knew it was coming, but the oft-delayed entry of the wide area augmentation system into the world of GPS is still somewhat startling in its potential.Īt the very least, WAAS promises more reliable and more accurate GPS coverage than ever before.
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