Seems to be a lot of confusion on when exactly these moves spike, especially the back air. I haven't seen a really clear explanation, (and I've ended up changing the explanations in my guide about three times), so I figured I'd try to clear it up.
The down air, for me, is the easiest to spike with, but it's not as powerful as the back air. The spike occurs at the fourth (final) hit at the very tip of Lucas's foot. You can hit with this by performing it above opponents as they jump or use a recovery move into it. I find it easiest to spike with when I use my jump and start the move as I rise. This should cause the first three hits in the move to stun the opponent in place while Lucas rises, placing the final hit right on target. If the move does not spike, it means the opponent is too far up when the final hit happens. Try positioning Lucas a little higher so just the tip of his foot connects with them. If your opponent's body makes contact with your own during the final hit, the spike will miss.
The back air is the one which seems to have the most confusion. Unfortunately, I find it really difficult to explain. For me, it's easiest to think of Lucas's back air as a half-hour portion of a clock. He begins the kick on the hour, and ends it at the thirty minute mark. The spike occurs from about the ten minute mark to about the twenty minute mark. However, in order to spike, you must hit with the very tip of his foot--not with the sparks, and definitely not further in toward his body. The very tip of his foot. You can actually see the area the spiking portion covers clearly in practice mode. Set the camera to zoom and the speed to 1/4, then perform Lucas's back air. You should see the sparks start right at the ten minute mark. Right at that point, Lucas's foot will extend. His foot then performs the kick until about the twenty minute mark before pulling back in to his body. You can only spike when Lucas's foot is extended. This attack can hit opponents at the uppermost and lowermost points, but for the spike you must hit your opponent with the very tip of Lucas's foot while his leg is extended--that is, anywhere from ten minutes to twenty minutes. Got it?
I find this is easiest if I'm falling toward an opponent from above. Be careful with the spacing so the opponent doesn't end up touching Lucas's body--opponents coming too close is the number one way of missing the spike. Perform the back aerial as you move down toward your opponent, aiming to hit with the 15 minute mark. This should give you a small margin of error either way in which the opponent will still be spiked. For practice, use a practice dummy set to "jump." Time your jump so you end up above them, performing the back air so that they jump right into the tip of Lucas's foot as it hits fifteen minutes.
In the case of either spike, do not aim to hit with the sparks of energy, and do not let the opponent touch Lucas's body. Hit with the tip of the foot only.
Hope this helps, and sorry if this has been covered in depth before.
The down air, for me, is the easiest to spike with, but it's not as powerful as the back air. The spike occurs at the fourth (final) hit at the very tip of Lucas's foot. You can hit with this by performing it above opponents as they jump or use a recovery move into it. I find it easiest to spike with when I use my jump and start the move as I rise. This should cause the first three hits in the move to stun the opponent in place while Lucas rises, placing the final hit right on target. If the move does not spike, it means the opponent is too far up when the final hit happens. Try positioning Lucas a little higher so just the tip of his foot connects with them. If your opponent's body makes contact with your own during the final hit, the spike will miss.
The back air is the one which seems to have the most confusion. Unfortunately, I find it really difficult to explain. For me, it's easiest to think of Lucas's back air as a half-hour portion of a clock. He begins the kick on the hour, and ends it at the thirty minute mark. The spike occurs from about the ten minute mark to about the twenty minute mark. However, in order to spike, you must hit with the very tip of his foot--not with the sparks, and definitely not further in toward his body. The very tip of his foot. You can actually see the area the spiking portion covers clearly in practice mode. Set the camera to zoom and the speed to 1/4, then perform Lucas's back air. You should see the sparks start right at the ten minute mark. Right at that point, Lucas's foot will extend. His foot then performs the kick until about the twenty minute mark before pulling back in to his body. You can only spike when Lucas's foot is extended. This attack can hit opponents at the uppermost and lowermost points, but for the spike you must hit your opponent with the very tip of Lucas's foot while his leg is extended--that is, anywhere from ten minutes to twenty minutes. Got it?
I find this is easiest if I'm falling toward an opponent from above. Be careful with the spacing so the opponent doesn't end up touching Lucas's body--opponents coming too close is the number one way of missing the spike. Perform the back aerial as you move down toward your opponent, aiming to hit with the 15 minute mark. This should give you a small margin of error either way in which the opponent will still be spiked. For practice, use a practice dummy set to "jump." Time your jump so you end up above them, performing the back air so that they jump right into the tip of Lucas's foot as it hits fifteen minutes.
In the case of either spike, do not aim to hit with the sparks of energy, and do not let the opponent touch Lucas's body. Hit with the tip of the foot only.
Hope this helps, and sorry if this has been covered in depth before.
