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When an airplane is on a long final approach (more than 200 feet above the touchdown zone), the ailerons and rudder have distinctly different responsibilities than when the airplane is on a short final. While on a long final, the ailerons are holding a heading and the rudder is simply ensuring coordination. If any crosswind exists, the airplane will be in a crab, with the heading of the airplane being determined by the pilot to defeat the crosswind. An airplane with a slow speed will have a bigger crab angle, and a faster one will have a smaller crab angle. A stronger crosswind will require a big- ger crab angle and a lesser crosswind will require less crab angle. Easy, right? Yes, easy.
But, what do the controls do during a short final? At some point in the ap- proach, usually about 100 feet (or so) above the runway, the pilot must make a mental shift and reposition the flight controls differently. The pilot must align the longitudinal axis of the airplane (line from nose to tail) with the alignment of the runway. So, the rudders have one (and only one) responsibility when land- ing: align the longitudinal axis with the runway. If a crosswind exists, the pilot must apply rudder pressure downwind to align the longitudinal axis with the centerline. When this rudder input is made in a crosswind, the airplane will drift from centerline unless something counters the effect of the crosswind. That something is the ailerons.
Ailerons correct for drift, and they do so by banking the wings and creating a horizontal component of lift. How much aileron does a pilot apply into the wind? Answer: Whatever it takes to keep the airplane on the centerline. A big cross- wind component will require more bank (forced by aileron control) and a small crosswind will require less bank. In other words, if the airplane lands off the center- line, the pilot f lew the ailerons poorly. If the longitudinal axis is not aligned with the runway alignment at touchdown then the rudder was flown poorly. Still easy, right? Yep, still easy. It’s piloting 101.
Now, when the pilot touches down, the tire on the side where the wind is coming from should touch down first due to the banked airplane. Remember, the pilot is holding aileron into the wind to defeat
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February 2019
TWIN & TURBINE • 7