Position Reference

Performance Initialisation Route Climbs Cruise Descent Direct Intercept Legs Departures and Arrivals Hold Progress Fix Previous page Next page

The Position Reference page does not have to be used on a normal preflight. It is presented here in a logical sequence because it is accessed from the Position Initialisation page.

Position Reference page 2 displays positions calculated by the FMC and IRS. Positions are displayed as the latitude/longitude calculated by the individual systems.

FMC POS - Displays the FMC calculated latitude/longitude.
IRS L - Displays the latitude/longitude of the L IRS.
IRS C - Displays the latitude/longitude of the C IRS.
IRS R - Displays the latitude/longitude of the R IRS.
RAD UPDATE PURGE - (SB changes with PURGE prompt on the POS REF page)

Used to remove the influence of radio updates from the FMC position. If the FMC determines that it is locked out of radio updating due to a position error, the PURGE UPDATES - POS 2 message is displayed.

When PURGE is displayed:
  • removes radio updates from FMC position
  • displays the IRS position (combined position of the 3 IRSs) on the FMC
  • changes the line title to PURGE ARMED and the prompt to CONFIRM


When CONFIRM is displayed:
  • sets the FMC position to the IRS position
  • allows radio updates to resume
  • increases the error term used to determine the validity of navaids to a value based on the time since the IRSs were aligned.
INDEX - Displays the INIT/REF INDEX page.
GS - Displays the current groundspeed from the FMC.
GS - Displays the current groundspeed from the L IRS.
GS - Displays the current groundspeed from the C IRS.
GS - Displays the current groundspeed from the R IRS.
Radio Update Station Mode - (SB changes with PURGE prompt on the POS REF page)
Displays the current mode of radio updating in the heading - either DME-DME, VOR-DME, LOC or NAV STA (no radio updating).

Displays the identifiers of the navaids being used for radio updating.
Displays the ROUTE page.

Pegasus | 11.40.20 | ROUTE>