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Installed on most of today's aircraft, a turn coordinator is a flight instrument designed to tell the pilot both an aircraft's rate of turn and quality of turn. A turn coordinator is broken down in to two components to relay each indication separately. The first part of the instrument consists of a miniature aircraft, viewed from behind, along with tick marks designating both straight flight and a standard-rate turn. A ball installed within a tube makes up the second component and resembles a construction level. This indicator relays information regarding the quality of the aircraft's turn.
Turn coordinators are installed on an aircraft's dashboard and are considered one of the pilot's primary instruments during flight. The miniature airplane component of the turn coordinator relays rate-of-turn information to the pilot and is a crucial component while flying under instrument flight rules (IFR). Turns during IFR should be made at the standard rate, which is 3° per second, and designated on the turn coordinator. This allows air traffic controllers to estimate how long an aircraft will need before completing the assigned turn. Using a rate of 3° per second, it will take an aircraft two minutes to make a complete 360° turn.
A turn coordinator's second component, sometimes referred to as the slip and skid indicator, tells a pilot if his aircraft is in coordinated flight. If the airplane is flying straight, the ball will be centered; otherwise, the ball will move to either side of the center. For example, if the aircraft is executing a left bank, yet the ball moves to the right, the aircraft is considered in a slip condition. If the ball moves in the direction of the bank, the plane is considered to be in a skid condition. The pilot must use his rudder pedals to maintain coordinated flight at all times.
Maintaining coordinated flight is crucial to the pilot for two reasons. Uncoordinated flight is less efficient, resulting in wasted energy and a higher consumption of fuel to perform the same amount of work. More importantly, uncoordinated flight results in a higher stalling speed. A higher stalling speed means the aircraft's wings will lose the ability to maintain flight earlier than normal — the cause of many aviation accidents and a dangerous situation for the pilot.
The basic turn coordinator operates using gyroscopes powered by the aircraft's electrical system. More sophisticated aircraft, such as commercial jets, utilize more sophisticated turn coordinators which make use of laser technology. In order to maintain safe and efficient flight, pilots on all types of aircraft must understand and make use of the information provided by their turn coordinator system.