Theory of Flight PDF

Theory of Flight THE AIRPLANE Airplane→​​ A ​power driven​ heavier than air aircraft deriving its lift in flight from aerodynamic reactions on surfaces that remain fixed under given conditions of flight. Aeroplane→​​ A heavier than air a...

Theory of Flight THE AIRPLANE Airplane→​​ A ​power driven​ heavier than air aircraft deriving its lift in flight from aerodynamic reactions on surfaces that remain fixed under given conditions of flight. Aeroplane→​​ A heavier than air aircraft deriving its lift in flight from aerodynamic reactions on surfaces that remain fixed under given conditions of flight. ○ I.e. A Glider CLASSIFYING AN AIRPLANE Many different ways of classifying an airplane… ○ Position of its wings in relation to the fuselage ○ # of engines ○ Type of wings high or low ○ Type of landing gear conventional or retractable PARTS OF AN AIRPLANE Components of an airplane are: 1. The fuselage or body 2. The wings or lifting surfaces 3. The tail section (empennage) 4. The propulsion system 5. Undercarriage or landing gear AIR FRAME The airframe of an aircraft is its mechanical structure It is typically considered to include… ○ fuselage, wings, undercarriage, fuel tanks... The parts that ​are not​ included are… ○ The propulsion system I.e. Engine ○ Instruments I.e. Air Speed Indicator, Vertical Speed Indicator, Altimeter… FUSELAGE Central body of an aircraft ○ Passengers, cargo and crew are located in here Many other parts of the aircraft are attached to it It is normally classified according to the type of construction… ○ Truss type Longerons​ are the principle members ○ Monocoque Consists of oval ​formers or bulkheads​ held together by ​stringers ○ Semi- Monocoque Type A ​combination​ of truss type and monocoque type Most commonly used fuselage type in general aviation today  Truss Type Monocoque Semi-Monocoque THE WINGS Biplanes → Have two pairs of wings Wing Layout → Many types Wing Construction ○ Wings have a… leading edge & trailing edge wing root & wing tip The members of the wing ○ Spars​​→ Run from ​wing root to wing tip ○ Ribs​​→ Run from the ​leading edge to the trailing edge Give the wind its shape provide a framework to which the covering is fastened An Airfoil→​​ Any surface designed to obtain a reaction from the air ○ I.e. Lift from the camber (the curvature of the airfoil) of the wing Wing Span→​​ The maximum distance from wing tip to wing tip Chord→​​ The imaginary line between the leading edge and the trailing edge of the wing ○ Also known as the width of the wing ○ Important in calculating aspect ratio Aspect Ratio:​​ span/chord ○ Divide the span of the wing (length of wing-tip to wing-tip) by the average chord (the width of the wing) THE EMPENNAGE The empennage is the rear portion of the airplane ○ Also called the tail ○ It is integral to control and stability during flight ○ Controls: Yaw ​(directional) Pitch​ (longitudinal) LANDING GEAR Type Definition Conventional (Tail-Dragger) Two main wheels and a tail wheel Tricycle Two main wheels and a nose wheel Retractable Wheels may be raised so that they are enclosed in wings or fuselage (reducing drag) Fixed Landing gear is not designed to retract Brakes ○ Provide a means of stopping the aircraft quickly ○ Assist with steering on the ground (these are called differential brakes) THE PROPULSION SYSTEM Generally a gasoline powered, air cooled, internal combustion engine that drives a 2 or 3 bladed propeller ○ Cowling→ ​encloses the engine and streamlines the front of the airplane to reduce drag ○ Engine mount→​​ The structure that supports the engine (steel tubes welded together) ○ Firewall→ ​ heavy sheets of stainless steel that separate the main structure and the engine CONSTRUCTION MATERIALS Stress: ​a force, or a combination of forces, ​exerting a strain ○ Types of Stress Compression: “crushing” Tension: “stretching” Torsion: “twisting” Shearing: “cutting” Bending: “bending” Strain:​​ distortion in form​ due to stress AIRCRAFT CLASSES AND CATEGORIES Depends on their configuration and intended design application 1. Normal Category ○ Most small planes ○ Cannot handle excessive load 2. Utility Category ○ Instructing training pilots in special maneuvers 3. Aerobatic Category  ○ Can handle excessive load (6X the gross weight) 4. Commuter Category ○ Carry passengers ○ Limited capacity and weight 5. Transport Category ○ Air liners and other large airplanes 6. Additional Category ○ Used for special applications such as aerial fire-fighting, aerial photography, some military aircrafts etc. FOUR FORCES OF FLIGHT 1. Thrust→ ​ The force exerted by the engine and its propeller which pushes air backward that causes a reaction, or thrust, in the forward direction 2. Drag→​​ The resistance to forward motion directly opposed to thrust 3. Lift→​​ The upward force which sustains the airplane in flight 4. Weight→​​ The downward force due to gravity, directly opposed to lift AXIS OF ROTATION 1. Longitudinal Axis a. Extends lengthwise through the fuselage​ (from nose to tail) b. Movement about this axis is roll c. Controlled with ailerons 2. Lateral Axis a. Extends crosswise from wing-tip to wing-tip b. Movement about this axis is pitch c. Controlled by elevators 3. Normal/Vertical Axis a. Passes vertically through the centre of gravity b. Movement about this axis is yaw c. Controlled by rudders *All axes pass through the centre of gravity → Point which is the centre of the airplane’s total weight AERODYNAMIC COUPLES A couple will cause a turning moment about a given axis ○ Lift and Weight When lift > weight → the aircraft will ​climb When weight > lift → the aircraft will ​descend ○ Thrust and Drag When drag > thrust→ the aircraft will ​slow down When thrust > drag → the aircraft will ​speed up Equilibrium ○ When two forces are equal and opposite, but parallel ○ *When the aircraft is in a state of equilibrium, thrust and drag and lift and weight are equal and opposite WING PLANFORM The shape of the wing as seen ​from above FLAPS Flaps increase the camber of the wing which, in turn, ​increases more lift ○ The negative pressure on top of the wing increases ○ There is a greater pressure under the wing They give better take-off and landing performance Flaps​ increase drag​ as well ○ The steeper the degree setting, the more drag is produced SLATS & SLOTS They are both fitted to the leading edge of the wing They are used to ​create a smoother airflow​ over the wings Slats Slots At high angles of attack, slats Passageways built into the wing automatically ​move out ahead of the ○ Do not move wing ○ The low pressure that sits behind the leading edge of the wing pulls the slat out SPOILERS SPEED BREAKS Devices on the wing that​ increase drag and decrease lift Usually used on high performance aircrafts Some spoilers are linked to ailerons or brake controls They ​create drag​ without altering the curvature of the wing Usually fitted far enough back to ​not disturb too much lift AIRSPEED LIMITATIONS White arc→ Flaps range Green arc→ Normal range Yellow arc→ Caution range Red line→ Never exceed VNE:​​ Never Exceed Speed VNO​​: Maximum Structural Cruising Speed or Normal Operating Limit Speed VSL​​: Power Off Stalling Speed (clean configuration) VFE​​: Maximum Flaps Extended Speed VSO​​: Power Off Stalling Speed (flaps and gear down) VA:​​ Manoeuvring Speed VB​​: Maximum Gust Intensity Speed DRAG There are two main types of drag… 1. Parasite Drag a. Created from parts of aircraft that​ do not produce lift i. Ex. Landing gear b. There are two types… 1. Form drag​​→ Form or ​shape of a body on the aircraft a. Ex. fuselage 2. Skin friction​​→ Tendency of air flowing over a body to​ cling to its surface a. Ex. dirt, dust, water 2. Induced Drag a. Created from parts of the aircraft that produce lift i. Ex. Wings b. *High aspect ratio wings produce less induced drag GENERATION OF LIFT Bernoulli's Principle​​: An increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy Newton’s Second Law: ​The acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object. ○ Helps explain that an aircraft can achieve lift because of the shape of its wings They are shaped so that that air flows faster over the top of the wing and slower underneath. High Velocity (fast moving air) → Low Air Pressure Low Velocity (slow moving air) → High Air Pressure ANGLE OF ATTACK Angle between the ​relative airflow and the chord CENTRE OF PRESSURE The average location of all pressures distributed over the airfoil ○ Relationship between Angle of Attack and Centre of Pressure As AoA increases up to the point of stall, CoP will move forward; beyond this point it will move backward rapidly STREAMLINING Designing the aircraft in order to minimize drag AILERON DRAG When banking, the downgoing aileron produces more drag than its counterpart ○ As a result, the airplane will yaw in the opposite direction To resolve this problem, two types of ailerons are used 1. Differential ailerons​​:​ downgoing aileron creates a smaller angle than the upgoing aileron​, balancing the drag created 2. Frise ailerons:​​ streamlined ailerons that ​pivot on a hinge​ and direct airflow Overall result: ​adverse yaw Differential Ailerons Frise Ailerons BOUNDARY LAYER Thin sheet of stationary air​ adjacent to the body of the aircraft ○ I.e. wings As the wing moves through the air the boundary layer goes through 3 stages 1. Laminar layer 2. Transition point 3. Turbulent layer ANGLE OF INCIDENCE Angle at which the wing is ​permanently inclined to the longitudinal axis Does not change WASH-OUT / WASH-IN Reduce the chance of stalling the aircraft Design a wing that ​stalls at wing root first Gives pilots aileron control ○ Wash out Decreasing angle of incidence Decreases lift ○ Wash in Increasing angle of incidence Increases lift STABILITY Stability ○ The tendency o​ f an airplane in flight to remain in straight, level, upright flight and to return to this attitude, if displaced, without corrective action by the pilot Static Stability ○ The initial tendency​ of an airplane, when disturbed, to return to the original position Dynamic Stability ○ The overall tendency​ of an airplane to return to its original position following disturbances 3 Types of Stability 1. Positive:​​ develop forces that ​restores​ airplanes original position 2. Neutral:​​ no forces present; airplane will ​neither return to original position nor move further away 3. Negative:​​ develop forces that ​moves the airplane further away​ from the original position Axis Stability… ○ Longitudinal Stability Stability around the​ lateral axis Pitch stability Affected by… Size and position of horizontal stabilizer Position of Centre of Gravity  ○ Lateral Stability Stability around the ​longitudinal axis Roll stability Affected by… Dihedral, Sweepback, Keel effect Distribution of weight ○ Directional Stability Stability around the ​vertical axis Yaw stability Affected by… Vertical tail surface (fin) FLIGHT PERFORMANCE FACTORS Torque ○ Causes the plane to ​yaw left​ since the propeller spins clockwise Asymmetric Thrust ○ Also known as P factor ○ At high angle of attack, down going propeller has a greater angle of attack ○ Therefore, more lift is produced from the right side of the plane, causing the plane to ​yaw left Precession ○ Change in plane of rotation of gyro Ex: suddenly change from nose up to nose down attitude → plane will yaw to the left Slipstream ○ Corkscrew motion of air causes different pressures on either side of the tail ○ Since air flows from high pressure to low, the plane will yaw to the left ○ Corrected by offsetting the fin EFFECT OF FLIGHT MANEUVERS Turns ○ The steeper the angle of bank (irrespective of speed), the… Greater the rate of turn Smaller the radius Higher the stalling speed Greater the loading (Gs) ○ The higher the airspeed (irrespective of angle of bank), the… Slower rate of turn Larger the radius Stall ○ Wing becomes incapable of generating enough lift to counteract the weight ○ Stall at any airspeed/attitude if the critical angle of attack is exceeded Spin ○ Wings are stalled​ (no aileron control) ○ Plane rotates towards ground at ​constant and low airspeed Spiral Dive ○ Excessive nose down attitude ○ Airspeed is rapidly increasing PITOT STATIC INSTRUMENTS Pitot pressure system + Static Pressure source 3 most common instruments… 1. Altimeter 2. Air Speed Indicator (ASI) 3. Vertical Speed Indicator (VSI) ERROR IN PITOT STATIC INSTRUMENTS Altimeter ○ Pressure error When flying from a high pressure area to a low pressure area, the altimeter will read higher than true altitude and vice versa “From high to low, look out below” “Low to high, clear blue sky” ○ Temperature error A higher temperature will cause the true altitude to increase above the altimeter referenced altitude Follow correction card to make up for error Air Speed Indicator ○ Density→ Caused by variable weather ○ Position→ Corrected using calibration chart ○ Lag→ Mechanical error ○ Icing → Blockage of pitot tube ○ Water→ Water in the system Vertical Speed Indicator ○ Lag→ Very common GYRO INSTRUMENTS Based on gyroscopic inertia and precession ○ 3 Most common instruments 1. Heading Indicator 2. Attitude Indicator (artificial horizon) 3. Turn and Slip Indicator ○ Other Turn Coordinator Compass