SF4 Boxer Question

So I’ve been toying around with dash ultra and thought in theory, TAP -> fadc -> dash ultra would work. But it seems like it doesn’t, anyone know why, or it doesn’t work just because it doesn’t work.

Thanks

TAP doesn’t do enough hit stun for you to combo a grounded ultra out of it after an FADC.

If you can catch your opponent in the air with a TAP however, you can usually juggle them with an ultra without needing to FADC.