This supposedly only works on Crows Nest.

When you get into the pelican launch hangar (Rally Point Alpha) there will be Phantom Dropships deploying Grunts, Jackals and Brutes then flying out of the hangar.

Before the Phantoms retreat, climb onto one of those yellow pylons (if you can't get onto the pylon, fetch a Deployable Cover and jump on the Phantom with that), kill the Grunt on the gunners seat and while holding RB jump into the gunners seat (don't worry about the Grunt behind you but you can kill the bastard if you like) and you should attach to the Plasma Turret like any normal turret.

When the Phantom retreats you will go with it out of the hangar with the other Phantom behind you (if there is one). Then after about a minute the Phantoms will fall dead to the ground but they will not be destroyed, I think you automatically get out of the gunners seat without being able to get back in but you can flip the dead Phantom by pressing RB, then realising you are wasting your time on flipping a Phantom that won't even fly.