Small experiment was conducted which found that a target lock key "TAB" is not working properly.
If the gunner of a helicopter gunship or a plane (after selecting the self-guided anti-tank missiles) tries to capture the target key "TAB":

1. If an enemy tank is empty, the engine is switched off - target lock does not work.
2. If an enemy tank with the enemy within, the engine is never turned on - target lock does not work.
3. If an enemy tank with the enemy within, the engine is started - target lock works.
4. If an enemy tank with the enemy within, the engine was turned on, then off - target lock works!
5. If an enemy tank is empty, the engine is on - target lock does not work!

This means that the "TAB" checks whether there is an enemy in armored vehicles. If there is an enemy in armored vehicles - a target lock is running. If there is no enemy in armored vehicles - a target lock does not work. This also means that the armor will destroyed even if the engine is not running. Both cases are not correct. In Arma 2 has not been this problem, because it worked as follows:

1. If an enemy tank is empty, the engine is switched off - target lock does not work.
2. If an enemy tank with the enemy within, the engine is never turned on - target lock does not work.
3. If an enemy tank with the enemy within, the engine is started - target lock works.
4. If an enemy tank with the enemy within, the engine was turned on, then off - target lock does not work!
5. If an enemy tank is empty, the engine is on - target lock works!

I think that the a target lock has to work in the same way as in Arma 2, as in Arma 2 "TAB" checks enabled \ disabled engine in armor (which makes sense), but not in the presence of enemy armor, which is not really possible.
Then as a target lock now works leaves no chance of survival for armored vehicles. In Arma 2 in armored vehicles have a chance to survive if you have time to turn off the engine. In Arma 3 is no such chance!