In aviation

Aviation

Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...

, coordinated flight of an aircraft

Aircraft

An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 is flight without sideslip

Slip (aerodynamic)

A slip is an aerodynamic state where an aircraft is moving somewhat sideways as well as forward relative to the oncoming airflow. In other words, for a conventional aircraft, the nose will not be pointing directly into the relative wind .A slip is also a piloting maneuver where the pilot...

.

When an aircraft is flying with zero sideslip a turn and bank indicator

Turn and bank indicator

In aviation, the turn and bank indicator shows the rate of turn and the coordination of the turn. The rate of turn is indicated from a rate gyroscopically and the coordination of the turn is shown by either a pendulum or a heavy ball mounted in a curved sealed glass tube. No pitch information is...

 installed on the aircraft’s instrument panel usually shows the ball in the center of the spirit level. There is no lateral acceleration of the aircraft and occupants perceive their weight to be acting straight downwards into their seats.

Particular care to maintain coordinated flight is required by the pilot when entering and leaving turns.

Advantages

Coordinated flight is usually preferred over uncoordinated flight for the following reasons:

• it is more comfortable for the occupants
• it minimises the drag
  Drag (physics)
  In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
  
   force on the aircraft
• it causes fuel to be drawn equally from tanks in both wings
• it minimises the risk of entering a spin
  Spin (flight)
  In aviation, a spin is an aggravated stall resulting in autorotation about the spin axis wherein the aircraft follows a corkscrew downward path. Spins can be entered intentionally or unintentionally, from any flight attitude and from practically any airspeed—all that is required is sufficient yaw...
  
  

Instrumentation

Airplanes and helicopter

Helicopter

A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...

s are usually equipped with a turn and bank indicator

Turn and bank indicator

In aviation, the turn and bank indicator shows the rate of turn and the coordination of the turn. The rate of turn is indicated from a rate gyroscopically and the coordination of the turn is shown by either a pendulum or a heavy ball mounted in a curved sealed glass tube. No pitch information is...

 to provide their pilots with a continuous display of the lateral balance of their aircraft so the pilots can ensure coordinated flight.

Glider pilots attach a piece of coloured string to the outside of the canopy to sense the sideslip angle

Sideslip angle

Sideslip angle, also called angle of sideslip , is a term used in fluid dynamics and aerodynamics and aviation. It relates to the rotation of the aircraft centerline from the relative wind...

 and assist in maintaining coordinated flight.

Axes of rotation

An airplane has three axes of rotation:

1. Pitch – in which the nose of the airplane moves up or down. This is typically controlled by the elevator
   Elevator (aircraft)
   Elevators are flight control surfaces, usually at the rear of an aircraft, which control the aircraft's orientation by changing the pitch of the aircraft, and so also the angle of attack of the wing. In simplified terms, they make the aircraft nose-up or nose-down...
   
    at the rear of the airplane.
2. Yaw – in which the nose of the airplane moves left or right. This is typically controlled by the rudder
   Rudder
   A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...
   
    at the rear of the airplane.
3. Roll (bank) – in which one wing of the airplane moves up and the other moves down. This is typically controlled by aileron
   Aileron
   Ailerons are hinged flight control surfaces attached to the trailing edge of the wing of a fixed-wing aircraft. The ailerons are used to control the aircraft in roll, which results in a change in heading due to the tilting of the lift vector...
   
   s on the wings of the airplane.

Coordinated flight requires the pilot to use pitch, roll and yaw control simultaneously. See also flight dynamics

Flight dynamics

Flight dynamics is the science of air vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw .Aerospace engineers develop control systems for...

.

Coordinating the turn

If the pilot were to use only the rudder to initiate a turn in the air, the airplane would tend to "skid" to the outside of the turn.

If the pilot were to use only the ailerons to initiate a turn in the air, the airplane would tend to "slip" towards the lower wing.

If the pilot were to fail to use the elevator to increase the angle of attack

Angle of attack

Angle of attack is a term used in fluid dynamics to describe the angle between a reference line on a lifting body and the vector representing the relative motion between the lifting body and the fluid through which it is moving...

throughout the turn, the airplane would also tend to "slip" towards the lower wing.

However, if the pilot makes appropriate use of the rudder, ailerons and elevator to enter and leave the turn such that sideslip and lateral acceleration are zero the airplane will be in coordinated flight.