In a straight flight, the

tail The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammal ...

of the airplane aligns the

fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraf ...

into the

relative wind In aeronautics, the relative wind is the direction of movement of the atmosphere relative to an aircraft or an airfoil. It is opposite to the direction of movement of the aircraft or airfoil relative to the atmosphere. Close to any point on the su ...

. However, in the beginning of a turn, when the ailerons are being applied in order to bank the airplane, the ailerons also cause an

adverse yaw Adverse yaw is the natural and undesirable tendency for an aircraft to yaw in the opposite direction of a roll. It is caused by the difference in lift and drag of each wing. The effect can be greatly minimized with ailerons deliberately designed to ...

of the airplane. For example, if the airplane is

rolling Rolling is a type of motion that combines rotation (commonly, of an axially symmetric object) and translation of that object with respect to a surface (either one or the other moves), such that, if ideal conditions exist, the two are in contact ...

clockwise (from the pilot point of view), the airplane yaws to the left. It assumes a crab-like attitude relative to the wind. This is called a

slip Slip or SLIP may refer to: Science and technology Biology * Slip (fish), also known as Black Sole * Slip (horticulture), a small cutting of a plant as a specimen or for grafting * Muscle slip, a branching of a muscle, in anatomy Computing and ...

. The air is flowing crosswise over the fuselage. In order to correct this adverse slip, the pilot must apply

rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally air or water). On an aircraft the rudder is used primarily to counter adve ...

(right rudder in this example). If the pilot applies too much rudder, the airplane will then slip to the other side. This is called a skid.

Stall

The skid is more dangerous than the slip if the airplane is close to a stall. In the slip, the raised wing — the left one if the airplane is turning to the right — will stall before the lowered one, and the airplane will reduce the bank angle, which prevents the stall. In the skid, the lowered wing will stall before the raised one, and the airplane will tighten the turn, and the stall can develop to a spin. At high altitudes, there is plenty of space for recovery. But during the final approach, when the airplane is close to the ground, a stall-spin accident is often fatal. A common cause of this accident is to enter a skidding turn in the airfield traffic pattern on the turn from base leg to final approach, unconsciously using excessive rudder in an attempt to tighten the turn and avoid overshooting the runway centreline.John S. Denker, ''See How It Flies''. http://www.av8n.com/how/htm/snaps.html#sec-skids

Deliberate skid

Deliberate skids are used in

aerobatics Aerobatics is the practice of flying maneuvers involving aircraft attitudes that are not used in conventional passenger-carrying flights. The term is a portmanteau of "aerial" and "acrobatics". Aerobatics are performed in aeroplanes and glide ...

and aerial combat. Deliberate slips done with vigorous application of roll and opposite rudder (lower the right wing and step on the left rudder) can be used as a dive brake. By balancing the roll's turn to the right with the rudder's yaw to the left, the plane continues to fly straight ahead but it presents its side rather than its nose to the airstream. The drag from this aerodynamically "dirty", clumsy position slows the otherwise sleek airplane. By modulating the amount of skid with rudder and aileron, the pilot can modulate the braking. Thus the plane can be slowed quickly in level flight or the descent to a landing can be dramatically steepened while holding the approach speed to a desired value.

References

Aerodynamics {{Aviation-stub

Stall

Deliberate skid

See also

References