Top Decay in Topcolor-Assisted Technicolor

Conventional technicolor models with light charged technipions ($\pi ^{\pm} _T$) lead to an unacceptably large contribution to $t\ra {\pi ^+_T} b$ decay rate. Topcolor-assisted technicolor models also have additional PGBs called top-pions ($\pi ^{\pm}_t$) which may contribute to this decay. We study the potentially dangerous mixing of charged top-pion and technipions in toy models of `natural' topcolor-assisted technicolor. We find that the $t\ra {\pi ^+_{t,T}} b$ decay rate in such models can be within experimental limits due to a combination of heavy top-pion and small $\pi _t - \pi_T$ mixing.