Just like in the original C&C, the Chinook is an unarmed transport helicopter. It will work just like the other vehicles (when you're inside, you'll get that nifty "third person" view), but there are no guns inside, outside, or on the Chinook.

And I'm willing to bet that you won't be able to "stand" on the aircraft at all, with those big rotors and all, so midair nuke attacks are probably not going to happen.