FMC Question

[zachlog 18]

Per the manual, the NAV RAD button is used for specifying VORs and ADFs. What I don't understand is how this information is used. How can these stations be used for navigation ? Are they supposed to be used for actual navigation or are they informational only ? Unlike other aircraft, there is no NAV function for capturing the course (CRS) specified in the NAV1 radio (I am aware of PB/D waypoints, etc., and their use in the FMC).I would appreciate some guidance for the FMC's NAV RAD button.Zach

[FLEX1978 373]

They are used for Raw navigation due to IRS drift (would you trust the map display 100% on a CATIII3B Approach?) also they are used to partialy update the FMC. This is a very basic answer and I'm sure someone else will give you more info.Rob

[downscc 1,327]

Read the AOM (Pg 7-4 Navigation Radios). You can use the VOR for navigation but the primary use is for FMC calculation of position along with the other sources.