Reference button

On a number of threads I see people describing the use of the reference button for a final alignment of the Viggen Nav system while aligned on the starting runway.

This has confused me (an easy thing to accomplish) as I though (from the plane manual) the reference button only reset the Nav reference altitude , and that the Nav position fix was manually updated using the Tv button while the radar is off.

What have I missed please?

Hi,

I think that when you are on the ground, with LS as the waypoint, pressing the ref button just re align the whole flight plan in reference to the starting runway heading (that’s why you need to be perfectly aligned before pressing the button). If not doing this, the nav system realignment is done automatically during the takeoff run and if you have crosswind, drift due to wind, it may then introduce some error.

Pierre

You dont need to use reference button to alling your INS.

When you start up the VIGGEN, leave your NAVIGATION SELECTOR in EBR mode, dont switch on your HUD. When you are on runway and well alligned with it, switch to NAV mode. Run up with stage 2 and when you reach 250km/h, your INS system alligned it self.

If you land (after your mission) and you have to take off again, repeat these steps but, in this case, you have to use the reference button(when you're in the center of the runway) because INS system alligned it self just one time.

P.S.: sorry for my bad english...