Crab landing
From Wikipedia, the free encyclopedia
A crab landing is a method of landing a fixed-wing aircraft in a crosswind.
A landing with a strong crosswind is one of the most technically difficult and dangerous maneuvers in aviation, and the crab-landing technique combined with elements of other techniques is widely considered one of the best ways of handling such a situation. In a crab landing, the plane flies along the center of the runway during approach. In order to maintain its position over the center, the nose is pointed off-center, slightly into the wind. Thus the longitudinal axis of the aircraft is at an angle to the runway while its ground track is along the extended centerline of the runway.
In a traditional crab landing, the plane descends in this manner, and then the pilot kicks the plane around at the last second in order to orient the nose of the plane parallel with the runway with the rudder pedals. This is very tricky to do correctly, and must be timed perfectly—if the pilot turns too soon, the plane will be blown off the runway, but if he turns too late, the landing gear will not be aligned with the runway and he risks seriously damaging or breaking it and possibly crashing the plane. Even if the pilot rotates the plane at the correct moment, the plane will still begin to drift with the wind as soon the crab angle is reduced, so the landing gear will have to absorb some side load on touchdown.
Because of these huge risks, most pilots advocate crabbing for the majority of the descent, and then changing to the slip technique when at a low altitude over the runway and using that for the rest of the descent. This is often referred to as the 'crab and slip' method. However, landing gears (e.g. those of commercial airliners) are designed to withstand enormous side forces so that if the plane touches down with a significant crab angle, it won't necessarily be damaged.
There are an extremely small number of planes which have a special landing gear which can be rotated with respect to the plane. This is required because their outboard engines are too far out on the wing and too close to the ground and would scrape the ground if the slip technique was to be used. This feature of the landing gear enables the crab landing technique to be used throughout the entire descent, without the need to execute the dangerous turn at the very last moment before touchdown. The B-52 Stratofortress is an example of this.
