Originally Posted by MSOCS
The fact that aircrew spend 99% of their sortie time using the HUD (i.e "primarily" using it) is another matter.
Again, no. The HUD is certified and taught as the primary flight instrument. This was/is the case for Tornado F3, F-15, Typhoon and Rafale - to my knowledge. I would be surprised if it were different on any other recent/current type. HUDs are designed with the intention of being the primary flight instrument. There would be no point in putting all the important stuff - attitude, heading, nav info, airspeed, altitude, ROC/D, etc, if it wasn't certified for use.