Airfoil & Wing

Module 3

3.1 Airfoil Overview
3.2 NACA series
3.2 Thin Airfoil Theory
3.3 Wing Geometry
3.4 Wing Lifting line Theory
3.5 Numerical Problems
3.1 Airfoil Overview
Airfoils – Overview
Airfoil Terminology
  • Leading Edge: The front, rounded part that meets the airflow.
  • Trailing Edge: The rear, tapering edge where air leaves.
  • Chord Line: Straight line connecting leading and trailing edges; its length is the chord (c).
  • Camber: The curvature of the airfoil; the distance between the chord line and the camber line (mid-point curve).
  • Thickness: Distance between upper and lower surfaces, often expressed as a percentage of the chord.
  • Angle of Attack (AoA): Angle between the chord line and the relative airflow direction.
Airfoil Visualizer

Airfoil Nomenclature

Leading Edge
Trailing Edge
Chord Line
Camber Line
Max Thickness
Max Camber

Airfoil Nomenclature

  • Geometric Angle of Attack (α): The angle between the chord line and the common reference line (often the horizontal axis of the aircraft).

  • Induced Angle of Attack (α_i): The angle by which the local airflow is deflected (downwash) compared to the free-stream velocity.

  • Absolute/Aerodynamic Angle of Attack (α_aero): The total angle from the zero-lift line to the local relative velocity.

  • Zero Lift Line: The orientation of the airfoil at which no lift is generated. For cambered airfoils, this is usually a few degrees "below" the chord line.

    • Airfoil Nomenclature - Updated Coordinates
    Sign Convention: Downward deflection = +α
    —Chord Line: Reference Axis
    ---Local Velocity: Local V∞
    3.2 NACA series

    Airfoil NACA Series

  • The NACA airfoil series is a standardized set of aircraft wing cross-sections developed by the National Advisory Committee for Aeronautics (NACA), the predecessor to NASA. These shapes are defined by mathematical formulas that use numerical codes to specify critical geometric properties such as camber and thickness.
  • Four-Digit Series
  • Five-Digit Series

  • Six-Series (Laminar Flow)

  • 1-Series (or 16-Series)

    • 3.2 Thin Airfoil Theory

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    3.3 Wing Geometry
    Wing geometry
    Wing Parameters
    • Span (b) Total distance from wingtip to wingtip.
    • Chord (c) Distance from leading edge to trailing edge.
    • Root Chord (Cr) Chord length measured at the fuselage centerline.
    • Tip Chord (Ct) Chord length measured at the wingtip.
    • Wing Area (S) Projected area of the wing (Span × Mean Chord).
    • Aspect Ratio (AR) Span squared divided by wing area; measures slenderness.
    • Taper Ratio (λ) Ratio of tip chord to root chord (Ct/Cr).
    • Sweep Angle (Λ) Angle of the edge relative to a perpendicular line from the fuselage.
    • Twist Angle A change in airfoil angle from the wing root to the tip. An aerodynamic feature added to aircraft wings to adjust lift distribution along the wing.
    • Washout (Negative Twist): Most common design; the wingtip has a lower angle of incidence (or attack) than the root, making the root stall before the tip, preserving roll control.
    • Wash-in (Positive Twist): Tip incidence is higher than the root; used in specific cases like forward-swept wings (e.g., X-29) to counteract tip stall tendencies.
    • Geometric Twist: A fixed change in airfoil angle (e.g., angle of incidence) from root to tip.
    • Aerodynamic Twist: Achieved by using different airfoil shapes (different zero-lift angles) along the span, even if the geometry looks similar.
    Wing Design Lab - Dual Column

    Wing Design Parameters

    Area (S)-
    Root Cr-
    MAC-
    Y-MAC-
    X-MAC Offset-
    Tip Ct-

    bCrMACY_MAC
    Aeronautical Wing Geometry Lab

    Wing Geometry & Configuration Lab

    Interactive technical guide to aircraft planforms and aerodynamic properties.

    Planforms

    Rectangular

    Easiest to manufacture and offers forgiving stall behavior.

    Example: Piper PA-38

    Elliptical

    Near-ideal lift distribution with minimal induced drag.

    Example: Supermarine Spitfire

    Tapered

    Better efficiency than rectangular, easier to build than elliptical.

    Example: Cessna 182

    Sweptback

    Delays transonic drag. Essential for high-speed commercial flight.

    Example: Boeing 787

    Delta Wing

    Low wave drag and high strength. Includes Ogival and Double Delta variants.

    Example: Concorde / Saab Draken

    Variable-Sweep

    Optimizes performance for both low-speed and supersonic regimes.

    Example: F-14 Tomcat

    Blended Wing

    Maximizes efficiency and stealth by making the entire aircraft a lifting body.

    Example: B-2 Spirit
    Aeronautical Wing Geometry Lab

    Wing configuration

    Interactive technical guide to aircraft planforms and aerodynamic properties.

    Lateral Stability Features

    +

    Dihedral

    Upward angle of wings for enhanced lateral stability.

    Example: Boeing 737-800
    -

    Anhedral

    Downward angle of wings to decrease stability and increase maneuverability.

    Example:Antonov An-124
    3.4 Wing Lifting line Theory

    Numerical Problems


    Developed by Dr. Aishwarya Dhara

    3.5 Numerical Problems

    Numerical Problems


    Developed by Dr. Aishwarya Dhara

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