Hallo,

 

Trying to get familiar with all modes of IRS update I ended up trying to use RWY REMAIN feature of the IRS update in lieu of GPS or other position update features. 

 

However trying everything I couldn't see it in action. First test was with VOR L/R DME L/R, ILS L/R and GPS L/R set as failed and IRS set with slight offset coordinates. Afterwards I taxied the aircraft to the end of the runway, selected the correct runway and depressed TO/GA. 

 

Second test was with not failures but in NAV STATUS> NAV OPTIONS page I have turned off DME, LOC, VOR and GPS updates and used an intersection takeoff and entered the remaining runway in RWY REMAIN field. Upon selection of TO/GA in both cases the position didn't update to the runway threshold (or THR + distance) and remained in the wrong coordinates.

 

Can anyone confirm if they have tested this previously? Is my testing method flawed? Or is the feature actually not implemented?

 

Thank you,

 

Seems it don't want to update. Runway identifier and shift value on take off ref are not highlightened also, however they should during TOGA update.

 

And yes, you update FMC position, not the IRS.