Slip (aerodynamic)

A slip is an aerodynamic state where an aircraft is moving 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. Flying in a slip is aerodynamically inefficient and can also cause motion sickness in passengers. Inexperienced pilots will often enter slips unintentionally during turns by failing to coordinate the aircraft using the rudder; however there are common situations where a pilot may enter a slip deliberately by using opposite rudder and aileron inputs, most commonly in a landing approach at low power. Without a slip it is difficult to increase the steepness of the glide without adding significant speed. This excess speed can cause the aircraft to fly in ground effect for an extended period, perhaps running out of runway. In a slip much more drag is created, allowing the pilot to dissipate altitude without increasing airspeed, increasing the angle of descent (glide slope). Additional airspeed will further increase the steepness of descent.
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