Pilot's Guide

190-00663-03 Rev. A
Garmin G1000 Pilot’s Guide for the Beechcraft C90A/GT/GTi
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APPENDIX D
FREQUENTLY ASKED QUESTIONS
If a particular aspect of G1000 operational capability is not addressed by these commonly asked questions or in
the index, contact Garmin (see the copyright page or back cover for contact information) or a Garmin-authorized
dealer. Garmin is dedicated to supporting its products and customers.
WHAt iS SBAS?
The Satellite Based Augmentation System (SBAS) uses a system of ground stations to correct any GPS signal
errors. These ground stations correct for errors caused by ionospheric disturbances, timing, and satellite
orbit errors. It also provides vital integrity information regarding the health of each GPS satellite. The signal
correction is then broadcast through geostationary satellites. This correction information can then be received
by any SBAS-enabled GPS receiver.
SBAS is designed to provide the additional accuracy, availability, and integrity necessary to enable users to rely
on GPS for all phases of flight.
There are several SBAS systems serving different parts of the world. The Wide Area Augmentation System
(WAAS) is currently available in the United States, including Alaska and Hawaii. The European Geostationary
Navigation Overlay Service (EGNOS) offers coverage of Europe, parts of the Middle East, and parts of northern
Africa. The Multi-functional Satellite Augmentation System (MSAS) covers mainly Japan.
HoW DoeS SBAS AFFect APPRoAcH oPeRAtionS?
Both LNAV/VNAV and LPV approaches use the accuracy of SBAS to include vertical (glide path) guidance
capability. The additional accuracy and vertical guidance capability allows improved instrument approaches to
an expanded number of airports throughout the U.S.
The implementation of RNAV LP and LPV approaches further improves precision approach capabilities.
RNAV LPV approaches are designed to make full use of the improved GPS signal from the SBAS. This approach
combines localizer precision lateral guidance with vertical guidance similar to the typical Instrument Landing
System (ILS). RNAV LPV approaches allow lower approach minimums.
WHAt iS RAiM AnD HoW DoeS it AFFect APPRoAcH oPeRAtionS?
RAIM is an acronym for Receiver Autonomous Integrity Monitoring. RAIM is a GPS receiver function that
performs the following functions:
• Monitors and verifies integrity and geometry of tracked GPS satellites
• Notifies the pilot when satellite conditions do not provide the necessary coverage to support a certain phase
of flight
• Predicts satellite coverage of a destination area to determine whether the number of available satellites is
sufficient to satisfy requirements
For RAIM to work correctly, the GPS receiver must track at least five satellites. A minimum of six satellites is
required to allow RAIM to eliminate a single corrupt satellite from the navigation solution.
RAIM ensures that satellite geometry allows for a navigation solution calculation within a specified protection
limit (2.0 nm for oceanic and en route, 1.0 nm for terminal, and 0.3 nm for non-precision approaches). The
G1000 System monitors RAIM and issues an alert message when RAIM is not available (see Appendix A).
Without RAIM, GPS position accuracy cannot be monitored. If RAIM is not available when crossing the FAF,
the pilot must fly the missed approach procedure.