Turn and Slip Indicator

The gyroscope of a turn and slip indicator is mounted yawing forces on the aircraft result in precession. This precession tilts the gyroscope left or right. A calibrated centering spring tries to return the gyroscope to the center position, and rate of turn is indicated.

A turn and slip indicator will be recognizable as a vertical needle which deflects left and right to indicate rate of turn. Marks on the indicator represent standard or and sometimes half standard rates of turn.

Turn Coordinator

A turn coordinator is recognizable has containing a miniature airplane as its method of indicating rates. The gyroscope of a turn coordinator is mounted at an angle, so that it detects both roll and turn rate. When a turn is initiated, the instrument will first show rate of roll. A rapid roll rate results in a steeper bank of the miniature airplane. The instrument then stabilizes to show turn rate.


Both turn and slip and turn coordinators contain integrated inclinometers. An inclinometer is simply a curved glass tube with a ball inside. In a coordinated turn, the ball is driven downward to the center of the tube. In uncoordinated flight, lateral forces throw the ball to another position in the tube.

Timed Turns

Turn and slip indicators and turn coordinators have markings which indicate when the airplane is being turned at standard rate. The standard rate of turn is 3 degrees per second. At this rate, it takes 2 minutes to complete a 360 degree turn.

Knowing this allows the pilot to make timed turns using the clock, which is often easier than relying solely on the compass. For example, if you wanted to turn 30 degrees right, you would establish a standard rate turn to the right for 10 seconds.

When maneuvering by reference to the instruments, turns are normally performed at standard rate. As airspeed increases, a greater bank angle is required to maintain a standard rate of turn. For this reason, pilots of high performance aircraft often use a 30 degree bank angle to maneuver and accept a lower than standard rate of turn, in order to avoid excessive angles of bank. Many autopilots are programmed to use a 25 degree bank angle for turns. In a small, single engine airplane, a standard rate turn might be accomplished with just a 15 or 20 degree bank angle because of the slower airspeeds flown.

Attitude and Heading Reference System

Many aircraft are equipped with an AHRS ("ahars"), which replaces the gyroscopes of a traditional flight instrument installation. These systems are solid state devices which often include integrated inertial sensors, rate gyros, magnetometers, and satellite reception. The AHRS compiles these inputs into attitude and heading information, which it transmits to the flight displays.

Air Data Computer

An air data computer receives and processes pitot-static pressures and total air temperature to calculate precise altitude, indicated and true airspeeds, and static air temperature.

Airspeed, altitude, vertical speed, and other calculated values are transmitted to the flight displays.