turnbuckle. An adjusting device used in a run of aircraft control cable to adjust its tension. A turnbuckle consists of a brass barrel and two threaded cable terminals made of steel. One terminal and one end of the barrel have left-hand threads, and the other terminal and the other end of the barrel have right-hand threads. The cable terminals are both started into the barrel, and as the barrel is turned, the terminals both screw into it. Screwing the terminals into the barrel increases the cable tension by shortening the cable.
turn coordinator (aircraft flight instrument). A rate gyro instrument that shows at a glance when a standard-rate turn is being made. The dial has a symbol which represents the rear of an airplane with marks that align with its wing tip when a standard-rate turn of 3° per second is being made. A black ball in a curved glass tube below the airplane symbol shows when the angle of bank is correct for the rate of turn being made.
The rate gyro is mounted in a canted gimbal (a tilted mounting frame) that allows the gyro to precess, or roll over, when the aircraft rotates about either its vertical or longitudinal axes. The gyro sensing rotation about both axes makes the instrument more sensitive and gives a more accurate indication of the condition of a turn than that shown by a turn and slip indicator.

turning error (magnetic compass error). See northerly turning error.