I recently re-watched Terminator 2: Judgement Day with a friend. When it came to the helicopter chase scene, my friend commented "He's reloading the gun, how is he still flying the helicopter?"
Now we've seen the T-1000 form knives and take on alternate forms, and at one point the T-101 punches through its head, and the T-1000 compensates by latching on, changing its head to hands, and growing a new head. So it seems fairly trivial for it to change one (or both) of its legs into an extra hand capable of flying the chopper whilst its other hands are busy shooting/reloading
Unfortunately it was on TV so we couldn't go back and check, but was the T-1000 using 3 hands in that scene?