[Captain-Ahmed]

The following guidelines are advised by Boeing for a crosswind landing. These guidelines assume steady wind (no gusting). These winds are measured at 33ft/10 m. Tower height for a runway 148 feet/45m. in width. Basically, there are 3 landing techniques which may be used to correct for cross winds: De-Crab, Crab, and Sideslip.


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De-Crab





The objective of this technique is to maintain wings level and the aircraft position near the runway centerline during approach. The nose points into the wind so that the aircraft approaches the runway slightly skewed with respect to the runway centerline (crabbing). This gives the impression of approaching the runway flying sideways, which can be disorienting for the pilot. Position is maintained by balancing the crosswind component, or more accurately the drag force arising from it, with engine thrust. Wings are maintained level throughout the approach. Right before the flare, opposite rudder (downwind rudder)is applied to eliminate the crab, with a simultaneous application of opposite aileron to maintain a wings-level attitude, so that at touch down, the body, velocity vector, and bank angle are all aligned with the runway, and the aircraft is positioned near the center.




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Crab



This is similar to the De-Crab technique. The principal difference is the aircraft touches down whilst still crabbing. The position on the runway is corrected after touch down. This applies significant slip angle to the tires, and increases the lateral loads on the undercarriage, so this technique is bounded by speed restrictions and is not generally recommended.






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Sideslip



This requires a higher level of skill. The purpose of this technique is to maintain heading aligned with the centerline. The initial phase of the approach is flown using the Crab technique to correct for drift. The aircraft heading is adjusted using rudder and ailerons to align with the runway. This places the aircraft at a constant sideslip angle, which its natural stability will tend to correct. Sufficient rudder and aileron must be applied continuously to maintain the sideslip at this value. The dihedral action of the wings has a tendency to cause the aircraft to roll, so aileron must be applied to check the bank angle.
With a slight residual bank angle, a touchdown is typically accomplished, for the cross wind direction shown, with the right main wheels touching down just before the left wheels. Excessive control must be avoided because over-banking could cause the engine nacelle or outboard wing flap to contact the runway/ground.
In strong crosswind conditions, it is sometimes necessary to combine the crab technique with the sideslip technique.




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Reference

Boeing Flight Crew Training Manual

https://en.wikipedia.org