What is the primary difference between a skid and a slip?

The primary difference between a skid and a slip lies in the aircraft's relationship with its intended flight path and how the pilot inputs control inputs, particularly the rudder. A skid occurs when there is excessive rudder deflection to the inside of the turn, which can lead to an over-banked condition. This action causes the aircraft to turn tighter than it naturally would, potentially leading to loss of control or a stall. Essentially, a skid results from the pilot applying too much rudder in conjunction with bank, causing the wings to remain level or nearly level as the aircraft turns, which creates an imbalance between the lift and the aircraft's weight.

This understanding helps differentiate a skid from a slip, where the aircraft is not coordinated in a turn, and the nose may point slightly outside the turn due to insufficient rudder application. While the other options touch on components of flight dynamics, they do not effectively capture the primary defining factor of a skid as the outcome of excessive inside rudder input, making the response accurate in describing the nature of these flight conditions.