Position Reference
Position Reference page 2 displays positions calculated by the FMC, IRS, GPS and radio navigation receivers. The FMC position can be updated to IRS, GPS or radio position on this page.
Positions are displayed as the latitude/longitude calculated by the individual systems. When BRG/DIST is selected the IRS, GPS and radio positions are shown as bearing distance from the FMC position. 11.40.14
FMC (GPS) - The source used by the active FMC for position data is displayed next to the FMC line title. In the example, the FMC uses GPS for position data. Displays the FMC calculated latitude/longitude. Identifies the source for calculating the FMC position:
GPS - position calculated from GPS and inertial position data.
IRS - position calculated from inertial position data only.
RADIO - position calculated from navigation radio and inertial position data.
LOC-GPS - position is calculated from localizer, GPS and inertial data.
LOC-RADIO - position is calculated from localizer, navigation radio and inertial data.
LOC - position is calculated from localizer and inertial data.
IRS - Displays latitude/longitude position or the bearing and distance from the FMC position determined by the IRS. If the displayed position is derived from all three IRSs, (3) is displayed. If the position is from a single IRS then (L), (C), or (R) is displayed to indicate which IRS position is displayed.
GPS - Displays latitude/longitude position or the bearing and distance from the FMC position determined by the GPS.
RADIO - After airborne, displays latitude/longitude position or the bearing and distance from the FMC position determined by navigation radios.
RNP/ACTUAL - Displays the RNP and actual navigational performance (ACTUAL) of the FMC. Default RNP is in small font. Valid RNP entries are in the range 0.01 to 99.9. ACTUAL entry not allowed. When ACTUAL exceeds RNP, EICAS displays the UNABLE RNP message.
Note: The FMC stops GPS updating if GPS data accuracy degrades due to satellite availability or unfavourable geometry. Subsequently, the FMC receives updates from another system.
Note: The FMC stops GPS updating if GPS data accuracy degrades due to satellite availability or unfavourable geometry. Subsequently, the FMC receives updates from another system.
INDEX - Displays the INIT/REF INDEX page.
UPDATE ARM - Push:
arms FMC position update function
changes prompt to ARMED
adds NOW prompts to right side of INERTIAL, GPS, and RADIO lines
Push a NOW prompt key to update FMC position to the selected source.
ACTUAL - Displays actual navigation performance (ANP) of the IRS, GPS and navigation radios.
ACTUAL - Displays actual navigation performance (ANP) of the IRS, GPS and navigation radios.
ACTUAL - Displays actual navigation performance (ANP) of the IRS, GPS and navigation radios.
DME DME - Displays radio station identifiers. Position update mode is indicated in the line title:
DME DME
VOR DME
Line and title are blank when no radio position is computed.
LAT/LON - Push - alternates position data format between bearing/distance or latitude/longitude.
The page illustration is shown in the latitude/longitude display format. Latitude/longitude format displays are actual position. Bearing/distance display is relative to the FMC position.
The page illustration is shown in the latitude/longitude display format. Latitude/longitude format displays are actual position. Bearing/distance display is relative to the FMC position.