Using current A3 stable build (1.36.128579) and A2CO (1.63.112555), "canFire vehicle = false" with player as gunner for an undamaged helicopter with no ammo. Try attached mission. There is no problem with this per se, but biki page
https://community.bistudio.com/wiki/canFire
says that "This command checks only the damage value, not the ammo!"
Solution: change biki page to list correct behavior, or change canFire command to report "true" for undamaged vehicle with no ammo. {F25322} {F25323}