A turn coordinator is similar to a turn-and-bank indicator in that the pilot uses it to determine the rate of turn. Theexternal difference between the two instruments is that the turn coordinator uses the outline of an airplane to indicate the rate of turn instead of an airplane to indicator as the rate of turn instead of needle,as shown in Fig.1 .The turn coordinator has re placed the turn-and-bank indicator as the standard turn-rate-indicating instrument on many aircraft.