Aerodynamics: Physics of the Atmosphere

• The module covers basic aerodynamics for B1 and B2 certification.
• Key topics include physics of the atmosphere, aerodynamics, theory of flight, and flight stability and dynamics.
• The study of aerodynamics is crucial for aviation maintenance technicians to ensure aircraft airworthiness and proper functioning.

Physics of the Atmosphere

• Air is considered a fluid because of its ability to flow and assume the shape of its container.
• Atmospheric pressure is the force exerted against the Earth's surface by the weight of the air. It is measured using a barometer.
• Pressure decreases with altitude.
• Density is weight per unit of volume.
• Air density varies directly with pressure and inversely with temperature.
• Humidity is the amount of water vapor in the air; higher temperatures allow air to hold more water vapor.
• The International Standard Atmosphere (ISA) provides standard values for pressure, temperature, humidity, and density for calculations and performance comparisons.

Aerodynamics

• Aerodynamics is the study of the dynamics of gases, focusing on the interaction between moving objects and the atmosphere.
• The relative wind is the flow of air around an object caused by the movement of either the air or the object, or both.
• Speed is the rate of motion in relation to time, while velocity is the rate of motion in a particular direction in relation to time. Acceleration is the rate of change of velocity.
• Newton’s laws of motion govern the action of air about a wing; inertia, F = ma, action/reaction.
• Bernoulli's principle states that when air flowing through a tube reaches a constriction, its speed increases and its pressure decreases.
• Laminar airflow is smooth, while turbulent flow is less consistent.
• The boundary layer is the layer of fluid in the immediate vicinity of a bounding surface.
• Skin friction drag is caused by the friction of a fluid against a surface and is related to the smoothness of the aircraft surfaces.
• Planform refers to the shape/outline of an aircraft wing as projected onto a horizontal plane. Wingtip vortices are created by pressure differences.
• Camber of a wing is the curve of the upper wing surface.
• The chord of a wing is the width of the wing.
• The angle of incidence is the acute angle the wing chord makes with the longitudinal axis of the aircraft.
• An airfoil is any part of the aircraft designed to obtain lift from the air through which it moves.
• Fineness ratio is a measure of the airfoil shape: specifically, defined as the ratio of the chord of the airfoil to its maximum thickness.
• Ice, snow and frost are typical forms of contamination, they alter airflow and laminar flow.
• The four forces acting upon an aircraft are thrust, weight, lift, and drag.
• An Aerodynamic Resultant represents the combined effect of all aerodynamic forces acting on the wing.
• Lift opposes weight, while drag opposes thrust.
• Angle of Attack (AOA) is the angle between the relative wind and the chord line of a wing.
• The Lift to Drag ratio (L/D) indicates airfoil efficiency.
• Parasite drag is any drag that isn't associated with the act of generating lift.
• Form drag (or pressure drag) from the pressure differential between the front/rear of an object and the wake it creates
• Friction drag is caused by the friction of a fluid against the surface of an object that is moving.
• Inducted Drag is an inevitable consequence of lift.
• Winglets help reduce inducted drag caused by wingtip vortices
• Wave drag is a forces, which occurs are speed close to Mac 1.0
• Parasitic Drag increases and total drag increases with the square of the airspeed.

Theory of Flight

• Lift acts vertically and counteracts the effects of weight.
• Lift is proportional to the square of the air velocity and also air density
• Thrust is the forward force produced by the powerplant, overcoming drag.
• The pilot can control lift by changing the AOA.
• Glide ratio is the distance the plane will travel forward compared to the altitude it loses. The best glide corresponds to the L/DMAX (Lift to drag ratio).
• A polar curve is a graph contrasting the sink rate fo an aircraft at a horizontal speed and is used mainly to illustrate the performance for a glider.
• When an aircraft bank, lift acts inward toward the center of the turn, as well as upward.
• A stall results from airflow no longer being smooth over the top surface and drag increases exponentially. When the "Critical angle" is reached, "Lift" is decreased and a stall occurs. When a stall happens the nose-down attitude is increased, thus reducing the angle of attack.
• Load factor are important to not overload the airframe of aircraft
• Service envelope refer to capabilites and limitations from the performance design package, suchs as airspeed and load factors at certain times.

High Speed Flight

• At speeds approaching the speed of sound it begins to experience the affects of "Compressibility", and compressibility causes a change in the density of the air around an aircraft.
• Subsonic is Mac number below 0.75
• Transonic is Mac number from 0.75 to 1.20
• Supersonic is Mac numbers from 1.20 to 5.00
• In short, air has to change to pass and this creates drag "waveform effect"
• Air speed is affected by speed and altitude, and requires pilots and technicians understanding changes of these speeds.

Lift Augmentation

• High-lift devices are usually fitted to the wing to increase "lift", during take-off, landing and low speed. The edge is normally the wing flaps and is known as flaps.
• Basic Flap, plain flap, split flap, slotted flap, Fowier flaps area all different components of flaps to the wing to increase lift and or drag.
• High-lift devices also can be applied to the leading edge , for ailerons, flaps.

Flight Stability and Dynamics

• Axes Of a Aircraft , whenever an aircraft changes it s attitude in a plane it must turn around three fixed access. They are , lateral , longitudinal , vertical access/pitch access.
• Stability is what gives the aircraft the capacity to fly "hands-off". Control are forces that allows air-craft with directional power in the best way to take off. Controllability is when pilot adjusts and maneuvers what has already happened.
• Longitudinal stability is where it involves the "Pitching/Lateral axes", making air craft stable on it side is now a quality.
• The three stages at the centre for air craft: With low speed, level flights and high speeds.

Lateral stability relies on four factors

• Dihedral - when "dihedral", this increases air-craft and decreases any movement, giving balance
• Sweepback - helps balance and prevent movement with air-craft. Helps level by force.
• Keel effect and Weight distribution Air-craft helps with any air movement.
• Vertical (Directional) - is simply stability of sideways movement, for air-craft fin is that are behind CG pivot.

Free Directional Oscillations (Dutch Roll)

• Is a balance coupling with lateral / directional oscillation. This is safe, but dynamic unstable due to the natural way damping is. This is a weaker mode and this is why you will see yaw damper.

Explore the basics of aerodynamics, including the physics of the atmosphere. Learn about atmospheric pressure, density, and humidity, and their effects on flight. Understand the International Standard Atmosphere (ISA) and its role in aviation maintenance.