Turn and bank indicator
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In aviation, the turn and bank indicator shows both the rate of turn and the coordination of the turn. The rate of turn is indicated gyroscopically and the coordination of the turn is shown by an inclinometer, which works in a way similar to a simple pendulum. No pitch information is provided.
The rate of turn is the actual rate at which the airplane is rotating. Tick marks, called "dog houses" because of their shape, generally show a 'standard rate turn'. The standard rate for most airplanes is 3 degrees per second, or 2 minutes per 360 degrees. One minute is often used in low speed aircraft like gliders, and 4 minutes is standard in high speed aircraft like the Concorde. The indicator is a white vertical needle. There are white markings at top center (for zero rate of turn), and one on each side, representing standard rate of turn to the left and right, respectively.
The coordination of the turn indicates whether the airplane is banked appropriately for its rate of turn. In an uncoordinated turn, the plane either slips or skids. In a properly coordinated turn, a passenger asked to point straight down would always point in the same direction relative to the airplane, straight into his seat, regardless of the actual bank angle of the plane.
The turn and bank indicator has been largely replaced by the newer turn coordinator. The turn and bank instrument is usually seen only on aircraft manufactured prior to about 1970.
A simpler way to see the coordination errors on some aircraft is to install a yaw string. This consists of a piece of wool 3 or 4 inches (8 or 10 centimetres) long taped to the center of the windscreen of the aircraft. The yaw string serves the same purpose as the ball in the turn and bank indicator except that it is more sensitive and removes the need to look at the instrument panel.