Aircraft Forces & Principles PDF

Stability Stalls Forces Theories and Principle Theories History overview Stability Stalls FORCES Forces Theories History overview  Axes of Motion Each axis of flight is an imaginary line around which an airplane can turn. Think of an airplane rotat...

Stability Stalls Forces Theories and Principle Theories History overview Stability Stalls FORCES Forces Theories History overview  Axes of Motion Each axis of flight is an imaginary line around which an airplane can turn. Think of an airplane rotating overview around an axis like a wheel rotates around an axle. Theories Stability History Forces Stalls In aviation though, their technical names are the lateral axis, longitudinal axis and vertical axis. Stability Stalls Forces Theories History overview  Controllability - is the response of an aircraft in steady flight on the pilot control input. Stability - can be described as the tendency of an overview Theories Stability History aircraft to return to trimmed position after Forces Stalls disturbance in an air stream. Maneuverability - can be described as the ability for the aircraft to commence and sustain maneuvers, its responsiveness and its performance rate of roll or turn and pitch rate.  Stability Stalls THRUST LIFT FLIGHT WEIGHT THE FOUR FORCES OF DRAG Forces Theories History overview Stability Stalls Forces Theories History overview  THRUST the forward force produced by the power plant/ overview Theories Stability History Forces Stalls propeller or rotor. It opposes or overcomes the force of drag. As a general rule, it acts parallel to the longitudinal axis  WEIGHT the combined load of the aircraft itself, the crew, the fuel, and the overview Theories Stability History Forces cargo or baggage. Weight is a Stalls force that pulls the aircraft downward because of the force of gravity.  Center of gravity The position of the center of gravity (CG), which is determined by the distribution of weight either by design overview Theories Stability History Forces Stalls or by the pilot, can also affect the longitudinal stability of an airplane. Stability Stalls Forces Theories History overview  DRAG a rearward, retarding force caused by disruption of overview Theories airflow by the wing, rotor, Stability History Forces Stalls fuselage, and other protruding objects. As a general rule, drag opposes thrust and acts rearward parallel to the relative wind  TYPES OF DRAG PARASITE DRAG overview FORM DRAG Theories Stability History Forces Stalls INTERFERENCE DRAG SKIN FRICTION DRAG INDUCED DRAG  PARASITE DRAG a rearward, retarding force caused by disruption of overview Theories Stability History airflow by the wing, rotor, Forces Stalls fuselage, and other protruding objects. As a general rule, drag opposes thrust and acts rearward parallel to the relative wind  FORM DRAG generated by the aircraft due to its shape and airflow overview Theories Stability History Forces Stalls around it. Examples the engine cowlings, antennas, and the aerodynamic shape of other components  INTERFERENCE DRAG overview Theories Stability History Forces Stalls comes from the intersection of airstreams that creates eddy currents, turbulence, or restricts smooth airflow  SKIN FRICTION DRAG is the aerodynamic resistance due to the contact overview Theories Stability History Forces Stalls of moving air with the surface of an aircraft.  INDUCED DRAG is inherent whenever an airfoil is producing lift and, in overview Theories Stability History Forces Stalls fact, this type of drag is inseparable from the production of lift. Consequently, it is always present if lift is produced. Stability Stalls INDUCED DRAG Forces Theories History overview Stability Stalls Forces DEFINITION OF TERMS Theories History overview Stability Stalls Forces AIRFOIL Theories History overview WHAT IS AN AIRFOIL? WHAT IS ITS PURPOSE? AIRFOIL LIFT 23 Parts of an airfoil Wing Components 24 Stability Stalls Forces Theories History overview  Upper Camber Mean Camber Leading 2 5 Line Edge Trailing Edge 1 9 Thickness 7 4 Camber 3 Lower Camber 6 Chord Line 8 Chord Length 26  LEADING EDGE Point of first contact between airfoil and moving air ALPINE SKI HOUSE 27  TRAILING EDGE Point of Last contact between upper and lower surface airflow ALPINE SKI HOUSE 28  THICKNESS Thickness Distance from the top and bottom surface ALPINE SKI HOUSE 29  CHORD LINE Imaginary line drawn between the leading edge and the trailing edge ALPINE SKI HOUSE 30  CHORD LENGTH Distance between the leading edge and the trailing edge ALPINE SKI HOUSE 31  CAMBER Camber refers to the curvature of the airfoil’s upper and lower surfaces. ALPINE SKI HOUSE CAMBER ALPINE SKI HOUSE  CAMBER Upper Camber – The curvature of the upper surface of an airfoil Lower Camber – The curvature of the lower surface of an airfoil Mean Camber Line - an imaginary line which lies halfway between the upper surface and lower surface of the airfoil and intersects the chord line at the leading and trailing edges. ALPINE SKI HOUSE 34 2 types of airfoils …  Types of an airfoils Symmetrical AIRFOIL - upper and lower surface of this airfoil is the same - Chord line and Camber line is the same Non Symmetrical AIRFOIL – upper and lower surfaces of this airfoil is different, also known as CAMBERED AIRFOIL -Chord line and Camber Line is different 36  Non symmetrical airfoil If the camber line is above the chord line, LIFT is generated upward If the camber line is below the chord line, LIFT is generated downward 37 RELATIVE WIND the direction of airflow in relation to an aircraft or airfoil 38 ANGLE OF ATTACK The angle of attack (AOA) is the angle at which the chord of an aircraft's wing meets the relative wind(V∞). Critical Angle of Attack - An angle at which the wing may stall - varies with every aircraft, approximately 16-20 degrees 39 Stability Stalls Forces Lift Production Theories History overview  LIFT is a force that is produced by the dynamic effect of the air acting overview Theories Stability History Forces on the airfoil, and acts Stalls perpendicular to the flight path through the center of lift (CL) and perpendicular to the lateral axis. In level flight, lift opposes the downward force of weight Stability Stalls Forces Lift Production Theories History overview  L = CL x ½ pV2 x S overview Theories Stability History Forces Stalls Lift = Lifting efficiency of the wing and its angle of attack X Dynamic Pressure X Surface area Stability Stalls Forces Bernoulli’s Principle Theories History overview  Bernoulli’s Principle states in part that "the internal pressure of a Fluid (liquid, or overview Theories Stability History gas) decreases at points where Forces Stalls the speed of the fluid increases."  Bernoulli’s Principle if the air flowing past the top surface of an aircraft wing is moving faster than the air flowing past the bottom surface, then overview Theories Stability History Forces Bernoulli's principle implies that the pressure Stalls on the surfaces of the wing will be lower above than below. This pressure difference results in an upwards lifting force. Stability Stalls Forces Newton’s 1 st motion Law of Theories History overview  Newton’s 1 st law of motion A body at rest tends to remain at rest, and a body in motion tends to overview Theories Stability History remain moving at the same speed and Forces Stalls in the same direction. Stability Stalls Forces Newton’s 3 rd motion Laws of Theories History overview  Newton’s 3rd Law of motion for every action there is an equal overview Theories Stability History Forces and opposite reaction. Stalls 3 FALLACIES OF HOW