Air units-> no use armorpiercing ammo.

[Epoletov___SPR]

Mi-24P it Weapon # 153 -- GH-30K

This weapon all over again uses HE ammo, and then AP at shooting on armour target!

Others gun at helicopters (Cobra, Ka-52) normally operate.

[Suhiir]

Helcopters are different from aircraft. They're flying vehicles and use AP ammo normally.

If you look ar aircraft only (class 11) weapons you'll see most have a higher kill value then ground weapons of the exact same type. This I assume simulates AP ammo since that slot s used for number of weapons for aircraft.