There seems to also be some confusion here about 'yawing', 'slipping' and 'balanced flight'. These are three different beasts that can occur completely independently of each other.
An aircraft flying straight and level is in balance, not yawing or slipping.
An aircraft in a traditional sideslip (constant heading) is slipping, out of balance but not yawing.
An aircraft in a balanced turn is in balance and yawing but not slipping.
An aircraft in a slipping turn is not in balance, but is slipping and yawing.
An aircraft in a rudder turn is out of balance, slipping and yawing.
A twin engine aircraft with one engine inoperative flying wings level is in balance, slipping but not yawing.
A twin engine aircraft with one engine inoperative flying at a zero slip bank angle is not in balance or yawing or slipping.
A twin engine aircraft with one engine inoperative in a balanced turn is in balance, slipping and yawing.
A twin engine aircraft with one engine inoperative flying with zero slip in a turn is yawing, but out of balance and not slipping.
9 permutations of three independent elements.
Last edited by Nomde plume; 25th December 2015 at 10:50.