The HUD has not been released yet. The 1.1.0 update says
"HUD System - Coming Soon!A fully modelled 3D HUD is coming soon! This will have dynamic projection, adjustable declutter settings, and collimated view effect. Accurate brightness levels and a new seating position ensure optimal usability. It also includes a unique feature, allowing the HUD symbology to shift relative to aircraft direction in challenging crosswind conditions, making crosswind landings even more manageable! Keep an eye out for this awesome addition, coming very soon!"
