Chicago’s O’Hare airport recently implemented its first RNP (required navigation performance) instrument approach. The satellite-based precision approach is part of the new generation of GPS approaches popping up at airports around the nation and the world. Chris Baur, president and CEO of Hughes Aerospace, the company that developed the approach, told the Aviation Examiner David W. Thornton on Wednesday that the new approach is an environmentally friendly alternative to current land-based approaches.
Instrument approaches are the procedures used by pilots to locate the landing runway when the weather precludes a visual approach. At large airports like O’Hare (KORD), the typical method of tracking to the runway involves an ILS (instrument landing system) approach. ILS approaches use land-based transmitters to send signals to the pilots that bring the airplanes to the touchdown point on the runway both laterally (with a localizer) and vertically (with a glideslope). This requires two separate transmitter facilities for each runway that utilizes an ILS. This can be cost-prohibitive for small airports.
RNP approaches utilize satellite navigation technology instead of ground-based navigational facilities. The aircraft’s flight management computer is programmed to fly a predetermined course along a series of waypoints, locations on a map that do not have to coincide with any geographic feature, toward the runway. Because the airplane is following GPS waypoints, approaches can easily be planned to avoid terrain features or noise sensitive areas. They can also be developed over water where land-based facilities are impractical. At some airports, RNP approaches even follow a curved path to the runway using RF (radius to fix) segments, such as this approach at Atlanta’s Peachtree-DeKalb airport (KPDK).
Check out the rest of the David W. Thornton’s story here!