A turn and bank indicator only shows "rate" of turn. The Cessna aircraft I learned on had an electric one with a mini airplane on it. As you banked you put the wing tip of the little airplane on an index and then knew you were in a standard rate turn. The problem is that this instrument does not show "bank" per se. In turbulence the wings rock and roll all over the place. It is a difficult skill to acquire to fly by turn coordinator. (turn and bank) only. For example if the pilot gets in to a steep spiral it can be very difficult to use only a turn and bank to recover.