Slip landing
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A slip landing is a technique for landing a fixed-wing aircraft in a crosswind. As the pilot begins his final approach, he corrects for the wind by angling the plane and using the ailerons and rudder.
Essentially, the rudder is used to keep the plane pointing in the same direction as it is traveling relative to the ground. The ailerons are used to keep the aircraft over the extended centerline. In this configuration, one wing will be lower than the other and the aircraft will not be flying (relative to the wind) in the same direction it is pointing. Part of the lift generated by the wings pulls the plane into the wind.
Because slips are uncomfortable for passengers and can increase the risk of the plane entering a spin, slips are generally not used for the entire descent. Pilots usually advocate a combination of the slip landing and crab landing techniques for the smoothest possible landings.
Prior to touchdown, it really does not matter which way the plane is pointing so long as it travels along the runway's extended centerline, so a crab is used during this portion. The plane is rotated into the wind to remain over the runway's extended centerline. Passengers remain comfortable and the plane continues to point in the direction it is moving relative to the air it is flying in.
Just before touchdown, the crab is converted into a slip. Rudder is used to align the plane's yaw angle to point straight down the runway. Because this removes the crab, the plane will start to lose runway alignment as the wind pushes. This is prevented by the application of opposite aileron. This slip is generally continued all the way until touchdown and the main wheels on the wing down side touch prior to the main wheels on the other side.
