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.
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Head, Tail and Cross Winds

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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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Wing Twist

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Image
  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.
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How to calculate Mean Aerodynamic Chord?

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Mean Aerodynamic Chord  The distance between leading and trailing edge of the wing, measured parallel to the normal airflow over the wing, is known as the chord. If the leading edge and trailing edge of the wing are parallel then, chord is constant along the span. Most commercial or fighter aircrafts have swept or delta wings in which chord length is greater at the root than at the tip. Consequently, chord changes along the span of the wing. The average length of Chord is known as Mean Aerodynamic Chord.  It has a geometrical importance as CG should be located at certain point of the MAC in percentage of its length. So, the location of MAC is specific and it can be found out as: Locating MAC Measure the root and tip chord and draw following points on plane : At the root of the wing, draw a line parallel to the fuselage centerline extending forward from leading edge and rearward from the trailing edge. Both lines should be the length of tip chord. Do the same thing at the tip but drawin
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NACA Airfoil Nomenclature

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The NACA airfoils are airfoil shapes for aircraft wings designed by National Advisory Committee for Aeronautics (NACA). The shape of NACA airfoils is identified by a logical series of digits following the word NACA such as "NACA 2412" . Every digit there signifies the dimensional properties of that airfoil. NACA series extend upto 8-series but the most commonly used are defined by 4-digit, 5-digit and 6-digit series. NACA 4- Digit Series In the 4-digit series, every digit tells about the dimension of the airfoil as per the order:  1.  - First digit describes maximum camber in percentage of the chord length c = 0.02c  2.  - Second digit tells about the location of maximum camber in tenths of chord length c = 0.3c  3.  - Last two digits signifies the thickness of airfoil in percentage of chord length c = 0.16c  NACA 5- Digit Series It has an additional parameter to emphasize for the performance parameter i.e. Lift coefficient, Cl. 1.  - 3/2 of first digit in tenths of chord giv
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