Ig-88b plus gunner gives you three attacks if you can miss the first one.
Only if done in the right order and with the right ship. So ships that have passenger and cannon slot that leaves the Slave 1, the YV-666 and the Mist hunter's tractor beam.
First attack misses triggering B's ability (using the hypothetical IG-88 crew card) fires a cannon shot say tractor beam which also misses. That triggers Gunner who make a primary firepower attack and no more attacks are made this turn.