For Video Lecture of this presentation: https://youtu.be/NAjezfbWh4Y The topics covered in this session are, drag, categories of drag, drag polar equation and drag polar graph, drag polar derivation, induced drag coefficient. Attention! "Gate Aerospace Engineering aspirants", A virtual guide for gate aerospace engineering is provided in "Age of Aerospace" blog for helping you meticulously prepare for gate examination. Respective notes of individual subjects are provided as 'Embedded Google Docs' which are frequently updated. This comprehensive guide is intended to efficiently serve as an extensive collection of online resources for "GATE Aerospace Engineering" which can be accessed free of cost. Use the following link to access the study material https://ageofaerospace.blogspot.com/p/gate-aerospace.html

1. FLIGHT MECHANICS
DRAG POLAR
Presented by - Ganesh Natarajan S
Target Audience: Gate Aerospace, Aerospace and Aeronautical Engineering Students, etc.

2. CORE TOPICS:
Basics: Atmosphere: Properties, standard atmosphere. Classification of aircraft. Airplane (fixed
wing aircraft) configuration and various parts.
Airplane performance: Pressure altitude; equivalent, calibrated, indicated air speeds; Primary
flight instruments: Altimeter, ASI, VSI, Turn-bank indicator. Drag polar; takeoff and landing;
steady climb & descent; absolute and service ceiling; cruise, cruise climb, endurance or loiter;
load factor, turning flight, V-n diagram; Winds: head, tail & cross winds.
Static stability: Angle of attack, sideslip; roll, pitch & yaw controls; longitudinal stick fixed &
free stability, horizontal tail position and size; directional stability, vertical tail position and size;
dihedral stability. Wing dihedral, sweep & position; hinge moments, stick forces.
SPECIAL TOPICS:
Dynamic stability: Euler angles; Equations of motion; aerodynamic forces and moments,
stability & control derivatives; decoupling of longitudinal and lateral-directional dynamics;
longitudinal modes; lateral-directional modes.
SYLLABUS

3. Outline
Let’s Start
DRAG POLAR
Previous Lecture Primary Flight Instruments
DRAG
• Definition
• Categories of drag
DRAG POLAR
• Equation & Graph
• Insights
DRAG POLAR: Derivation
• Induced drag co-efficient

4. DRAG
Definition
The aerodynamic force that opposes an aircraft's motion through the air is known as drag. In
common there are only two general types of drag namely,
• Pressure drag - Due to a net imbalance of surface pressure acting in the drag direction.
• Friction drag - Due to the net effect of shear stress acting in the drag direction.

5. • Skin-friction drag: Frictional shear stress integrated over the surface.
• Form drag: Pressure drag due to flow separation
• Profile drag: Skin friction drag + Form drag. (2D airfoils / section drag.)
• Parasite drag: Skin friction drag + Form drag. (Complete airplane configuration.)
• Interference drag: Total Drag - Drag due to individual component of the airplane.
• Induced drag: A pressure drag caused by the induced flow (downwash) associated with the
vortices created at the tips of finite wings.
• Zero-lift drag: The parasite drag at its zero-lift angle of attack, i.e., Lift = zero. (Complete
Airplane Configuration.)
• Drag due to lift: Parasite drag during non-zero-lift angle of attack + Induced drag
Categories of Drag – Subsonic Drag Definitions
Book Reference: Aircraft Performance & Design, J.D. Anderson. (2010). Pg.No: 113-114.

6. DRAG POLAR
The equation and the graph expressing relation between CD and CL are called the drag polar.
Drag polar reflect the aerodynamic information necessary for the performance analysis of an
airplane.
Total drag = parasite drag + wave drag + induced drag
In terms of co-efficient,
Drag Polar Equation:
Here
• CD = Total drag coefficient,
• CD,o = Zero-lift parasite drag coefficient,
• 𝐾𝐶𝐿
2
= Drag due to lift.

7. DRAG POLAR: Equation & Graph
PressureDistributionOverThinAirfoil-Gaurav–www.learnpick.in

8. DRAG POLAR: Equation & GraphByTSRL-Ownwork,CCBY-SA3.0,
https://commons.wikimedia.org/w/index.php?curid=19821696
Gopalarathnam,Ashok&Mcavoy,Christopher.(2002).Effectof
AirfoilCharacteristicsonAircraftPerformance.JournalofAircraft
-JAIRCRAFT.39.427-433.10.2514/2.2968.

9. DRAG POLAR: Insights
• Drag polar is nothing more than the resultant aerodynamic force plotted in polar
coordinates-hence the name drag polar.
• The locus of all such points for all values of α forms the drag polar.
• Drag polar provides the following information for performance analysis
 CL/CD, that is, lift-to-drag ratio.
 The tangent line - point of maximum lift-to-drag ratio for the airplane
 Design point for the airplane i.e. design lift coefficient for the airplane.

10. DRAG POLAR: Derivation

11. DRAG POLAR: Derivation

12. DRAG POLAR: Derivation
Gopalarathnam, Ashok & Mcavoy, Christopher.
(2002). Effect of Airfoil Characteristics on Aircraft
Performance. Journal of Aircraft - J AIRCRAFT. 39.
427-433. 10.2514/2.2968.

13. Book Reference
Aircraft Performance & Design, J.D. Anderson . (2010). Chapter 2 -
Aerodynamics of the Airplane: The Drag Polar Pg.No: (51-144/596).
DRAG POLAR

14. Summary
Drag & Drag
Polar
Drag polar:
Derivation
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