A typical objective after a touchdown is to have the aircraft lined up with the runway, regardless of the technique. Each approach has benefits and drawbacks. The benefits and drawbacks of each ᴍᴇᴛʜod should be understood if your aircraft is permitted to use more than one. You should follow the ᴍᴇᴛʜod recommended by your aircraft’s ᴍᴀɴufacturer and be aware of any restrictions. I’ve flown planes that deᴍᴀɴd a crab landing (T-38), deᴍᴀɴd sideslip landing only (B-707, T-37), let you employ any ᴍᴇᴛʜod with restrictions on the sideslip (B-747), or deᴍᴀɴd a just prior to touchdown.
The information that follows is based on the references listed below, along with my thoughts and ᴍᴇᴛʜods. Nobody explains the approaches more clearly than Boeing, and the majority of late-model Boeings support all three with a few restrictions. Each technique was introduced using the Boeing 737 NG Flight Crew Training ᴍᴀɴual as a starting point, with other aircraft being suggested for a different perspective. If the information in your ᴍᴀɴuals on cross-wind landings is lacking or quiet, the following might help.
The 737 technique that follows can be found in other Boeing ᴍᴀɴuals, thus it might not be exactly applicable to other aircraft that permit a touchdown in a sideslip. However, it gives you more information than you had if your handbook offers no advice at all or if you are seeking how “the big boys” do it.
The main gear touchdown on the extended runway centerline is made possible by the sideslip crosswind technique, which aligns the aircraft with it.
The crab ᴍᴇᴛʜod is used to fly the initial part of the approach to land in order to account for drift. The centerline of the aircraft is parallel to or on the centerline of the runway before the flare. In order to avoid drift, the longitudinal axis is aligned to the intended track using the downwind rudder, while the wing is lowered into the wind using the aileron. To maintain the desired course, a constant sideslip is created using an opposite rudder and a low wing against the wind.
The upwind wheels touch shortly before the downwind wheels to complete the touchdown. Over-banking could result in the outboard wing flap or engine nacelle making contact with the runway, hence it’s important to avoid over-controlling the roll axis.
When this ᴍᴀɴeuver is properly executed, the rudder and aileron control positions are almost fixed during the final stage of the approach, touchdown, and the start of the landing roll. However, since crosswinds and turbulence frequently coexist, it can be challenging to maintain cross-control coordination during the last part of the approach to touchdown.
When there are heavy crosswinds, it might be required to add a crab if the crew decides to fly the sideslip to touchdown. The upwind wing is lowered and the crab angle is used to make the main gear touchdown. To align the aircraft with the runway centerline as the upwind wing touches first, a modest increase in the downwind rudder is applied. To keep the wings level during touchdown, more upwind ailerons should be used.
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Video resource: DutchPilotGirl