Re: How do you use the TAC cannon?
Then head on out to the flight deck. You dont use the tac cannon on the 4 legged walker, you have to go to the left side of the flight deck where theres the crate of rocketlaunchers and take cover there. That will be your "office" for the remainder of the level. Sit there and keep grabbing rocketlaunchers and shoot at the top of the walker's head. You'll see pieces flying off it and smaller explosions. That means youre damaging him. Keep at it and soon he'll be brought down.
Once he goes down, a monster of a boss comes up over the side. Make sure you stay by where your rockets are. You have to destroy 4 turrets on the front of this guy. Theres 2 on the top left and right, and on the bottom left and right (on the torso, not the 2 things on the sides)
Once you destroy those turrets, the VTOL with doctor -whats-her-face will de-activate the shield on the left wing of the boss. Once done, take the tac cannon and nuke it. After thats done, they will go to the right side of the boss and deactivate that one. Nuke the wing on that side as well.
Once thats done, the thing will start to fly over the carrier. Take the rockets and shoot it at the blueish circle thing under the boss. It will open up and then the other delta guy will say NUKE THAT ****ER! Run back and launch the nuke into the blue center opening, and then run to the end of the flightdeck and jump in the VTOL.
Thats where the fireworks start smile