The HUD has four master modes:
WOW (Weight On Wheels).
NAV + APP (APP is a NAV submode)
AA
AG

Here is how it works now:

WOW overrides anything while the aircraft is on the ground.
NAV is default mode when in the air.
APP is NAV submode.
HUD changes to the appropriate mode based on selected weapon in the PCA or by HOTAS.
If not weapon has been selected, it will select AA Gun: CAN when you click Master Arm ON.
Here is how it must work:

WOW overrides anything while the aircraft is on the ground.
NAV is default mode when in the air.
APP is NAV submode.
AA mode is engaged only when selecting CAN or MAG by HOTAS.
Clicking on PCA HOTAS button will revert to NAV (only if neither 530 or POL are selected).
AA mode is engaged if either 530 or POL are selected in the PCA. Deselecting 530 or POL in the PCA returns to NAV.
Clicking on MAG in the PCA does not change into AA, nor does it returns to NAV if AA is engaged.
MAG option in the PCA is used to activate magic seeker search option. It does not select the missile for launch nor does it set the system in AA mode.
CAN and MAG HOTAS selection are overrides. System will ignore any PCA selection until you click the PCA HOTAS button.
Selecting any type of AG weapon in the PCA does not change the system to AG mode. Only the PCA changes to display weapons option in the top row.
To activate AG mode you must:
Select AG weapon in the PCA.
Click the Special Modes Switch Forward.
To return to NAV with AG weapon selected you must:
Click the Special Modes Switch Aft.
The Master Arm switch only authorizes weapons launch/release/fire. If no weapon is selected, nothing happens. System remains in NAV or APP.

What does this mean?
That during Air-to-Air engagements you can have all three weapons ready at your fingertip:
You preselect 530 in the PCA and then choose CAN, MAG or 530 by using the HOTAS buttons: CAN, MAG or PCA.

For Air-to-Ground operations this means that you can set your attack plan without losing NAV data. You enter AG mode only when you are ready.

As you can see this is a major change in the HUD/PCA functionality and it requires some time and testing to get it right.
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