10 - FDE175Section 10Fault Detection & ExclusionThe Garmin 400W-series software incorporatesa Fault Detection and Exclusion (FDE) algorithm,thus providing a basis for approval per FAA NoticeN8110.60 requirements for “GPS as a Primary Meansof Navigation for Oceanic/Remote Operations”.The FDE consists of two distinct features, faultdetection and fault exclusion. The fault detectionfeature detects the presence of an unacceptably largepseudorange error for a satellite (and presumably,position error) for a given mode of flight. Upon detec-tion, fault exclusion follows and excludes the sourceof the unacceptably large pseudorange error, therebyallowing navigation to return to normal performancewithout an interruption in service. To enhance safety,FDE functionality is provided for other phases of flight(non-precision approach, terminal, en route). The FDEfunctionality for non-oceanic flight phases complieswith missed alert probability, false alert probability andfailed exclusion probability specified by DO-229C /TSO-C146a.Detection and ExclusionAn FDE prediction must be performed prior todeparture for a flight plan involving Oceanic/Remoteoperation where GPS is to be the sole source ofnavigation. Prior to departure, the operator mustuse the FDE prediction program supplied with the400W/500W-series Trainer CD to demonstrate thatthere are no outages in the capability to navigateon the specified route of flight (the FDE predictionprogram determines whether the GPS constellation isrobust enough to provide a navigation solution for thespecified route of flight). Please, refer to the instruc-tions included in the Garmin 400W/500W-seriesTraining CD for complete details on using the FDEprediction program.
