The meat-and-potato point defense weapon in FreeSpace 2
it is used by every race and virtually every warship (GVC Aten
doesn't count), and some non-warships (GTFr Triton
) the GTC Aeolus
actually makes most of its warship kills with flak rather than its weak SGreen
Flak Turrets are more of a deterrent weapon, although they are still one of the more effective AA weapons in the game.
Flak is a very deadly weapon, the GTC Aeolus is proof of this.
Flak is primarily a danger to a fightercraft with a breached shield quadrant, ANY breached shield quadrant, even if it's on the other side of the fighter from the flak gun. Pay close attention to your shields and equalize their strength often if under flak fire.
As said above, if you have any breached quadrant, you're going to die soon. When you have to destroy the first Sathanas's beam turrets, you should pipe more power into the shields to avoid being killed by the flak. (If you go up close like I did.)
Flak's lethality is debatable. Most people seem to agree that flak won't kill you outright unless you stay in one place for too long and hold down the primary fire button like you would do in FS1. It's a distracter weapon keeps you on the move and bounces you around, but rarely kills a competent pilot. It is more effective against heavier, slower targets than light fighters. Some say that blob turrets are more effective against bombs than flak is.
It depends on the difficulty. On lower difficulties, flak may not hurt you at all, but on higher difficulties, flak can be very lethal in a short amount of time.
Flak cannons are actually fairly dangerous. Because even though flak rarely makes direct hits, its shells explode when they pass near a fighter. Prolonged exposure will bring down your shields and leave your hull open to one hell of a battering. On higher difficulties your shield simply evaporates in seconds and you're screwed. They're still relatively effective without weapons subsystem active unlike other more dependent weapons, such as beams.