Tre...
A "caged" HUD will LOCK the HUD Pitch Ladder and Velocity Vector to the middle, so you can see it, even in high wind conditions. Normally, an "uncaged" HUD Ladder will move side to side as well and can drift off the screen if the sidewinds are too high. "Caging" it locks it down and instead of moving left or right, you will see a "ghost" velocity vector, denoting where the wind is pushing you. The ghost v/vector looks like the regular v/vector without the circle. Instead, you will just see the three sticks. If you need pics, let me know. To enable, simply bring up the HUD Control Panel, and click ON the CAGE switch.
Also, you are close on TACAN. Press TCN, then "4" and "7" and Enter. Once entered, just make sure there is a green colon to the immediate left of the "X". The green colon ":" denotes selection/activation when using any of those 5 side menu windows on the HUD UP FRONT CONTROLLER.
Later
Sludge