Airfoils and Wings

Understanding airfoils and wings is essential for optimizing aircraft performance, enabling efficient lift generation, minimizing drag, improving stability, and supporting advanced aerodynamic design across subsonic, transonic, and supersonic regimes.

Course Outcome

This course is designed to equip students with fundamental and advanced aerodynamic principles, including airfoil behavior, lift and drag prediction, finite-wing effects, and compressibility considerations. They will gain skills to analyze and design wings using theories like thin airfoil and lifting line, enabling applications in aircraft design, UAV development, performance assessment, and aerodynamic optimization.

Pedagogical Approaches

Animated content, 3D Simulations, and Video lecture integrations

Prerequisite Subjects

Fluid Mechanics

Explore Lessons

1. Syllabus
2. Airfoils Nomencleture
3. Aerodynamic coefficients
4. Wing Theory
5. Test your knowlegde
5. Reference
1. Syllabus
Airfoil and Wing — Syllabus Timeline

Module 1: Airfoil Nomenclature

Module 2: Aerodynamic Forces and Moments

Module 3: Kutta Condition

Module 4: Thin Airfoil Theory

Module 5: Finite Wing Theory

Module 6: Prandtl Lifting line Theory

Module 7: Critical Mach Number

Module 8: Supercritical Airfoil & Area Rule

2. Airfoils Nomencleture
NACA & Airfoil Terminologies – Notes
1. Introduction to NACA
The National Advisory Committee for Aeronautics (NACA) was a U.S. federal agency founded on March 3, 1915 to conduct systematic research in aeronautics. Its mission was to improve aircraft performance, aerodynamic efficiency, safety, and scientific understanding of flight. In 1958, NACA was dissolved, and all its research centers, engineers, and projects were incorporated into the newly established NASA, forming the foundation of modern aerospace research.
2. What is a NACA Airfoil?
A NACA airfoil is a cross-sectional shape of a wing designed using numeric designations developed by NACA. These numbers encode aerodynamic characteristics such as camber, thickness, and pressure distribution. The most used series are: NACA 4-digit series NACA 5-digit series NACA 6-series (laminar flow airfoils)
3. Airfoil Terminologies
  • Camber – curvature of mean line
  • Maximum Camber – highest camber point
  • Thickness – maximum airfoil thickness
  • Leading Edge Radius – front roundness
  • Trailing Edge – rear sharp edge
  • Chord Line – Straight line connecting the leading and trailing edges
  • Mean Camber Line – A curve halfway between the upper and lower surfaces of the airfoil
4. NACA Series Concepts
NACA 4-Series: Defines camber, camber location, and thickness.
NACA 5-Series: Uses ideal lift coefficient and refined camber line.
NACA 6-Series: Designed for laminar flow and low drag.

NACA Airfoil Families – Advantages, Disadvantages & Applications

NACA FamilyAdvantagesDisadvantagesApplications
4-Digit 1. Good stall characteristics
2. Small center of pressure movement
3. Roughness has little effect 		1. Low maximum lift coefficient
2. Relatively high drag
3. High pitching moment 		General aviation, Horizontal tails, Supersonic jets, Helicopter blades, Shrouds, Missile fins
5-Digit 1. Higher maximum lift coefficient
2. Low pitching moment
3. Roughness has little effect 		1. Poor stall behavior
2. Relatively high drag 		General aviation, Piston-powered bombers, Transports, Commuters, Business jets
16-Series 1. Avoids low pressure peaks
2. Low drag at high speed 		1. Relatively low lift Aircraft propellers, Ship propellers
6-Series 1. High maximum lift coefficient
2. Very low drag (narrow range)
3. Optimized for high speed 		1. High drag outside optimum range
2. High pitching moment
3. Poor stall behavior
4. Susceptible to roughness 		Piston-powered fighters, Business jets, Jet trainers, Supersonic jets
7-Series 1. Very low drag (narrow range)
2. Low pitching moment 		1. Reduced maximum lift
2. High drag outside optimum
3. Poor stall behavior
4. Susceptible to roughness 		Seldom used
Airfoil Nomenclature​
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Application of Airfoil
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3. Aerodynamic coefficients
Aerodynamic Coefficients: Lift, Drag & Moment – Notes
1. About Aerodynamic Coefficients
Aerodynamic coefficients are non-dimensional parameters used to compare lift, drag, and moment across aircraft of different shapes and sizes. They normalize aerodynamic forces using dynamic pressure. Aerodynamic coefficients are non-dimensional parameters used to characterize the aerodynamic performance of an aircraft. They allow comparison of different aircraft shapes, sizes, wings, and operating conditions under a common scale. The main aerodynamic coefficients are: Lift Coefficient (CL) Drag Coefficient (CD) Moment Coefficient (CM)
2. Lift Coefficient (C_L)
Definition:
CL = L / (0.5 × ρ × V² × S)

CL increases with angle of attack until stall. Typical slope ≈ 0.1 per degree.
Cambered airfoils have higher CL compared to symmetric airfoils.
3. Drag Coefficient (C_D)
Definition:
CD = D / (0.5 × ρ × V² × S)

CD consists of parasite drag, induced drag, and wave drag.
The total drag polar is: CD = CD0 + CL² / (π × AR × e).
4. Moment Coefficient (C_M)
Definition:
CM = M / (0.5 × ρ × V² × S × c)

Indicates pitching behavior. Negative Cm means stable, nose-down moment.
Cambered airfoils generate a negative pitching moment.
5. Effect of Aerodynamic coefficients
CoefficientMeaningRoleDepends On
CLLift capabilityMinorAoA, wing shape
CDDrag producedMajorRe, surface condition
CmPitching momentCriticalCG, camber, tail size

Thin Airfoil Theory : Watch now

Import Airfoil in NASAOpen VSP: Watch now

4. Wing Theory
Wing, Wing Theory & Prandtl’s Lifting-Line Theory – Notes
1. Wing – Definition & Concept
A wing is a lifting surface that generates lift through aerodynamic forces. Its geometry—including span, chord, aspect ratio, sweep, and taper—determines its aerodynamic efficiency and structural behavior.
2. Wing Theory Overview
Wing theory explains 3D lift generation, including wingtip vortices, downwash, effective angle of attack, and induced drag. It connects 2D airfoil behavior to real aircraft wings.
3. Prandtl’s Lifting-Line Theory
Prandtl's theory models a finite wing as a bound vortex with trailing vortices, predicting spanwise lift distribution and induced drag. It is fundamental to modern aerodynamic design.

Different types of Winf Planform

Contract between Geometric and Aerodynamic twist

Derivation of Lifting Line Theory

Wing design using NASA OpenVSP

5. Test your knowlegde
NACA Airfoil Series - MCQ Quiz

NACA Airfoil Series - MCQ Quiz

1. Which NACA series defines camber, position, and thickness (e.g., NACA 2412)?

2. Which NACA series is a modification of the 4-digit with improved lift characteristics?

3. Which NACA series is designed for laminar flow over part of the chord?

4. In a NACA 4-digit airfoil, the first digit represents:

5. In a NACA 4-digit airfoil, the second digit represents:

6. In a NACA 4-digit airfoil, the last two digits represent:

7. Which NACA series introduced the idea of controlling pressure distribution for laminar flow?

8. Which NACA series often has designations like 23012?

9. Which series was developed later for better laminar flow?

10. The 6-series airfoils were designed primarily to:

5. Reference

1. Anderson, John D., Jr. A History of Aerodynamics and Its Impact on Flying Machines, Cambridge University Press , New York

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