Making pilots eject are based on several factors:
- The relative condition of your ships. If his ship is almost dead and your ship is pristine, then the chance is higher. If you have high amounts of energy left, that helps as well.
- How fast you deal the damage. If you dish out a lot of damage on a short period of time, they're more likely to bail.
- Your combat rating. The higher it is, the higher the %.
- The size of the ships. You aren't going to make heavy fighters bail as often if you are in a dinky scout.
There seems to be bail checks set at various levels of ship HP. If they don't bail at 90%, taking them down to 50% will trigger another chance. If they're almost dead (<10% hp), then no matter what you do to them they won't try to bail again, just finish them off.
Also, having a high shield but low hull damage weapon, like a pulsed beam emitter, helps a lot. Use that to zap away their shield real fast, then nibble away at the hull until they bail.
Finally, I don't know if Terrans will actually bail, at least in X3:TC, you couldn't make ATF ships bail.
If you take your PBE mounted fighter and go find a bunch of M5 and M4s, you'll get them to bail quite fast.