Flight Basics

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...

Airfoils are rather simple geometrical objects as they are nothing but a curve drawn on a flat plane of paper, defined by coordinates usually by two columns namely, x and y. They define airfoil as locus of points where each point is defined by a set of x and y coordinates. It can be created of 50 or 100 points depending on the chord length decided as per the requirements. To draw airfoils, you have various tools available like:-  1.   Software   They work on the airfoil coordinates available in dat file and use it to plot airfoil on the screen which can be printed afterwards. Some of the software available out there include Catia, Solidworks, AutoCAD, Xfoil and Concord (conversion of airfoil coordinates).  2.   Online plotter   It includes various websites having with them airfoil database which is available for all, you can just select airfoil needed from the list or else you can enter the details like LE radius, chord, camber to plot airfoil whi...

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 b...

Measuring speed on ground is much easier for vehicles like cars, buses, bikes, etc. by the use of speedometer but in the case of aircraft. Airspeed is not simply what you see inside the cockpit reading through the indicator. Depending upon the instrumentation terms and physical properties of air, Airspeed can be classified as : 1. Indicated Airspeed  Airspeed as indicated by the airspeed indicator inside cockpit that the pilot reference for speed changes. Indicated airspeed is the measured speed of an aircraft as it moves through the air, it is based on the pressure readings collected by the pitot-static system. It changes with the altitude as at higher altitudes the density of air is low and there are fewer molecules to enter the pitot tube and create pressure hence, Indicated airspeed decreases during climb. 2. Calibrated Airspeed Calibrated airspeed is the indicated airspeed corrected for instrument and positional errors. At certain airspeed and flap settings instrumental errors...

         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 l...

  Aerodynamic Center The aerodynamic center is the point on the chord at which the pitching moment coefficient does not vary with lift coefficient, i.e. angle of attack. It is the point where the aerodynamic forces are supposed to act, a fixed location on the chord. Lift and drag forces can be applied at a single point, where they exert zero torque, at center of pressure but it moves with angle of attack as pressure distribution changes thus, makes the aerodynamic analysis complex. For most low speed airfoils aerodynamic center lies at (1/4) of chord back from the leading edge in supersonic airfoils it is nearer to the (1/2) chord location. In case of symmetric airfoils the aerodynamic moment about ac is zero for all angles of attack. With camber, the moment is non-zero and constant for thin airfoils. For a positive camber airfoil the moment is negative and results in the counter-clockwise rotation of the airfoil.