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For B.E students
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Air Basics and Performance
02 Sep 15II Lecture
Basic Aircraft Terminology
• Aerofoil: Cross sectional shape of a wing• Leading Edge (LE): Front edge of the wing• Trailing Edge (TE) : Back edge of the wing• Chord Line: Line connecting LE and TE• Camber : Centre line between top and bottom
of wing
Aerofoil
Axes of an AircraftLongitudinal: Parallel to the FuselageLateral : Parallel to the WingNormal : Perpendicular to the ground
Axes of an AircraftLongitudinal: Parallel to the FuselageLateral : Parallel to the WingNormal : Perpendicular to the ground
Six degrees of freedom
Wing Layout• Sweep: Angle between the lateral axis and the
wing• Taper: Chord decreases as you move towards
the wing tip• Incidence: Angle between the longitudinal axis
and the wing chord• Angle of Attack: Angle between the wing and
the relative wind• Twist : Bending of wings about lateral axis– Anhedral (downward)– Dihedral (upward)
Wing Geometry Definitions
Angle of Attack
Wing Layout
• Aspect Ratio (AR) = Span ^2/wing area• More efficient of slow moving aircraft• Typical values– Glider : 20-30– Trainer: 7 -9– Loadstar: 18.5
Control Surfaces
• Ailerons: Horizontal surfaces located on wing tips– Roll: rotation about the longitudinal axis
• Elevator : Horizontal surfaces located on the tail– Pitch: rotation about the lateral axis
• Rudder: Vertical surface located on the tail– Yaw: rotation about the normal axis
Stabilising Surfaces
• Vertical Stabiliser : The vertical part of the tail which prevents unwanted yaw
• Horizontal Stabiliser: The horizontal portion of the tail that prevents unwanted pitch
Flaps
• Changes the shape of Wing• Increases Lift and Drag• Used during takeoff and landing
Flaps
• Changes the shape of Wing• Increases Lift and Drag• Used during takeoff and landing
Forces of Flight
• Lift • Drag • Thrust• Weight
For steady and level flight these four forces and the moments they generate must be in equilibrium. An airplane is a force and moment balancing machine
Forces of Flight
Force of Flight
Lift
• Controlled by– Airspeed, angle of attack, altering aerofoil and
altering the planform area– Lift= ½ *p * V^2*A*Cl p- density V- Velocity A- wing area Cl – coeff of lift
Co-efficient of Lift
Magic no of lift; determined experimentally
Constant for any size wing with same aerofoil
Accounts for unkownVaries with AoA
There is an angle where the wing produces zero lift
Explains how airplane can fly upside down
Loss of Lift
• Every wing has a stall angle• Stall angle is angle of attack at which wing
losses lift• Stall angle ranges from 12-20 degrees
Drag
• Form Drag- shape of the object• Skin Friction Drag- surface of object• Induced Drag- Component of Lift• Parasitic Drag= Form Drag+ Skin Drag• Total Drag= Parasitic Drag+ Induced Drag• Total Drag= ½ *p*V^2*A*Cd Cd – Co-eff of Drag. Determined
experimentally
Drag Curve