Wing Twist

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  Wing twist is of two types named as geometric twist and aerodynamic twist:- Geometric Twist Different angles of attack at wing root and tip. Wash in Tip chord has a higher angle of attack than that of root chord. Wash out Angle of attack at tip is lower than that at wing root. It is useful in reducing tip vortices. Aerodynamic Twist Difference between zero-lift lines of airfoils at wing root and near the tip. Airfoils at root and near the tip have different zero lift angles of attack.

Head, Tail and Cross Winds

        
Head Wind

A head wind is a wind that flows opposite to the direction of an aircraft, it is favorable in takeoffs and landings as an airfoil moving into a headwind is capable of generating greater lift. During headwind, ground speed of aircraft is equal to the difference of speed of aircraft and speed of wind. 



It allows aircraft to reach the lift off speed at a lower ground speed. Air-traffic controllers commonly choose to take off or land in the direction of a runway which will provide head wind. During cruise it will decrease performance by reducing ground speed which in turn increases the fuel requirement for the flight. 


Tail Wind

A tail wind is a wind that blows in the direction of travel of an aircraft hence, increasing the ground speed of the aircraft, and increases the takeoff distance. During tail wind, ground speed is just equal to the sum of aircraft speed and speed of wind. 


It provides a greater ground speed to attain the lift-off speed. During cruise, it will increase performance by increasing ground speed which in turn reduces the fuel requirements for the flight.

Cross Wind

A cross wind is any wind that has a perpendicular component to the line or direction of travel. This affects the aerodynamics of many modes of transport. During cross wind, ground speed is equal to the vector sum of aircraft speed and wind speed.



A crosswind is the component of the wind blowing across the runway making landing and take off difficult than if wind blowing straight down the runway. If cross wind is strong enough it can damage aircraft's undercarriage during landing. It induces sideslip during the flight which affects the directional stability.

The sideslip crosswind technique is to maintain the aircrafts heading aligned with the runway centerline, it is adjusted using rudder and ailerons to align with the runway. This places the aircraft at constant sideslip angle, which its natural stability will tend to correct but sufficient rudder and aileron must be applied continuously to maintain the sideslip at this value.  




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