Garmin G1000 Pilot's Training Guide (-05) - Page 8

• APV Approach with vertical guidance is an International Civil Aviation Organization (ICAO) term referring to specific ICAO criteria adopted in May 2000. This approach classification allows stabilized descent using vertical guidance without the accuracy required for traditional precision approach procedures. The US has developed criteria for lateral/vertical navigation (LNAV/VNAV) and LPV approach procedures that meet this approach classification. LNAV/VNAV and LPV approaches provide guidance in both the lateral and vertical planes. • SBAS Satellite-based augmentation systems use satellites and networks of ground stations to provide improved accuracy for received GPS satellite signals. Internationally, many countries are working with the International Civil Aviation Organization (ICAO) to standardize satellite-based augmentation systems (SBAS) globally. WAAS is an SBAS currently being implemented in the United States 2. Describe how WAAS provides improved accuracy. The Wide Area Augmentation System (WAAS) uses a network of ground stations to provide necessary corrections to received GPS SPS navigation signals. Precisely surveyed ground reference stations are strategically positioned across the country, including in Alaska, Hawaii, and Puerto Rico, to collect GPS satellite data. Using this information, a message is developed to correct any signal errors. These correction messages are then broadcast the same frequency as GPS signals by communication satellites to receivers on board aircraft. WAAS is designed to provide the additional accuracy, availability, and integrity necessary to enable users to rely on GPS for all phases of flight, from enroute through approach for all qualified airports within the WAAS coverage area. WAAS supplies two different sets of corrections: 1corrected GPS parameters (position, clock, etc.) and 2Ionospheric parameters. The first set of corrections is user position independent (i.e., they apply to all users located within the WAAS service area). The second set of corrections is area specific. WAAS supplies correction parameters for a number of points (organized in a grid pattern) across the WAAS service area. The user receiver computes ionospheric corrections for the received GPS signals based on algorithms which use appropriate grid points for the user location. Furthermore, the appropriate grid points may differ for each GPS satellite signal received and processed by the user receiver, since GPS satellites are located at various positions in the sky relative to the user. The combination of these two sets of corrections allows for significantly increased user position accuracy and confidence anywhere in the WAAS service area. 3. Explain the capabilities of TSO-C146a GPS equipment during instrument approaches, per the AIM. The equipment automatically utilizes WAAS error corrections for safe navigation of LNAV/VNAV instrument approaches. These approaches provide both horizontal and vertical guidance. This equipment can also navigate LPV approaches developed specifically for WAAS, providing ILS-like performance. 4. Equipped with TSO-C146a GPS equipment, what other navigational instruments must your aircraft have on board to navigate in National Airspace? Using TSO-C146a GPS equipment, a pilot could legally navigate solely by use of WAAS GPS, even in areas where VOR or NDB reception is poor or non-existent. All TSO C129/C129a systems require the presence of another approved navigation system appropriate to the intended route of flight. 4 GIFD Pilot's Training Guide 190-00368-05 Rev. B