Aircraft Turn Coordinator: Name, Differences, Advantage

The Turn Coordinator (TC) is a gyroscopic aircraft instrument that forms part of the basic aircraft six-pack. It combines two instruments into one, replacing the older turn and slip indicator with a more advanced design that displays the rate of turn and roll information while indicating whether the aircraft is coordinated. By providing a miniature airplane visual picture of roll rate, the turn coordinator can respond more quickly to the start of a turn, helping pilots establish and maintain a standard-rate turn.

Expert behind this article

Jim Goodrich

Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.

What is the other name for a turn coordinator?

There is no widely used separate name, the device is simply called a turn coordinator.

What instruments make up a turn coordinator?

The turn coordinator combines two instruments into one: a turn indicator (gyroscope) and an inclinometer. The gyroscope is mounted at a 30-degree angle upward in relation to the longitudinal axis of the aircraft, and it is housed in a double gimbal. This mounting angle allows the gyroscope to respond to both roll and yaw movements of the aircraft. The gyroscope spins at about 10,000-15,000 RPM and exhibits rigidity in space, maintaining its orientation regardless of aircraft movement. In the bottom part of the instrument, the inclinometer contains a small black ball sitting in a liquid-filled curved tube. The inclinometer ball indicates slip or skid by its position. When the ball drifts to the right, it indicates a skid. A small airplane symbol rolls depending on bank angle, providing visual indication of the aircraft's bank.

I understand that a turn coordinator is an integration of two separate instruments. The main unit is a gyroscope that represents velocity and rotation. An inclinometer, a tiny sphere incorporated into the same unit, reveals whether movement is unified.

Jim Goodrich

Pilot, Airplane Broker and Founder of Tsunami Air

What is the difference between a turn coordinator and a turn and slip indicator?

The difference between a turn coordinator and a turn and slip indicator is explained in the table below.

The core difference between a turn coordinator and a turn and slip indicator lies in what each gyro can sense. The turn and slip Indicator is sensitive only about the yaw axis and cannot determine yaw or roll. The turn and slip indicator provides slip skid indication via the ball in the inclinometer. An inclinometer is a liquid filled tube with a ball; the black ball moves to the outside of turn when skidding and to the inside when slipping. Therefore, the turn and slip indicator's ball in the inclinometer indicates slip or skid when not centered, giving the pilot a direct cue. Because the turn and slip indicator has a slip ball but no roll cue, the pilot must infer roll attitude from the bank index and the rate-of-turn needle.

The turn coordinator gyro is canted 30 degrees forward. Gyroscopic precession is used to displace the instrument indicator, so the miniature airplane banks proportionally to both roll and yaw. This combined presentation lets the pilot see an immediate roll command during recovery from unusual attitudes, whereas the older instrument delivers only yaw-rate information. Both instruments have an inclinometer, so the same ball indicates slip or skid in either case, but the turn coordinator adds the roll-rate dimension that the turn and slip indicator cannot determine.

What is the difference between a turn coordinator and attitude indicator?

A turn coordinator is electrically powered, and its canted gyro allows detection of rate of roll. An attitude indicator shows pitch and bank and is a vacuum powered gyroscope mounted inside gimbals to display aircraft orientation at an instant. Because of this construction difference, the attitude indicator controls pitch/bank position whereas the turn coordinator shows roll rate and coordination. When a partial panel situation occurs after attitude indicator failure, turn coordinator can serve as a performance instrument for limited aircraft control.

What is the difference between a turn coordinator and rate of turn indicator?

A turn coordinator and a rate-of-turn indicator both rely on a spinning gyroscope that exhibits rigidity in space and spins at 10,000-15,000 revolutions per minute, yet they display information differently. The rate-of-turn indicator presents a vertical needle; when no turn is detected the needle points to the index at the top of the instrument, and the standard-rate turn is indicated by index marks on the turn needle. Below the needle, the inclinometer - a liquid-filled tube containing a black ball - shows slip or skid.

In the turn coordinator the gyroscope is mounted at a 30-45 degree angle, with the front higher than the rear, so gyroscopic precession lets the instrument sense both roll and yaw. Instead of a bare needle, a miniature airplane symbol rolls right or left depending on the bank angle and the rate of turn, while the same black-ball inclinometer provides coordination guidance.

What is an advantage of an electric turn coordinator?

The advantage of an electric turn coordinator is that it remains functional when the vacuum pump fails. Traditional training aircraft use a mix of vacuum and electrical systems which provides redundancy. When the vacuum system fails, the electrical turn coordinator acts as a backup bank indicator. A canted gyroscope axis tilted to 30 degrees allows the indicator to respond more quickly to banking which allows autopilot systems to control bank rate.