[pdonis]

> Heading and altitude are NOT independent.

Yes, I know how planes make turns. It is valid to point out that a TCAS instruction that included a heading change would, at least for the plane whose TCAS instruction was to increase altitude, also have to include an engine power increase, which might not be feasible depending on the altitude (cruise power might already be pretty close to max power). Or else make the turn a very slow one, which would decrease its usefulness in collision avoidance.