Lecture 2: Airplane Aerodynamics

This paragraph introduces the fundamental question of how airplanes fly, emphasizing the importance of understanding this concept. It highlights the need to discuss airplane parts such as the propeller, fuselage, wings, tail, rudder, elevator, and landing gear. The paragraph also introduces the four main forces acting on an airplane: lift, weight, thrust, and drag, and their interrelationships for an airplane to achieve steady flight.

This section delves into the concept of lift, discussing its generation through the deflection of air and the conservation of momentum. It debunks the incorrect equal transit theory and emphasizes the significance of the airfoil shape in generating lift. The importance of understanding the correct theories of lift is stressed to avoid misconceptions.

This paragraph discusses Bernoulli's principle and its role in understanding how lift is generated. It explains the relationship between pressure and velocity in the context of an airfoil, and how this principle contributes to the lift force. The paragraph also touches on the FAA's requirements for understanding lift and introduces the concept of drag as the horizontal component of the force generated by an airplane.

This section broadens the discussion to include other objects moving through a fluid, such as race cars, and how they also generate lift. It explains that lift is not exclusive to airplane wings and can occur with any object moving through a fluid. The conversation then shifts to the factors affecting lift, including the object's shape, size, and the fluid's properties.

This paragraph discusses the complexity of calculating lift, acknowledging that while we understand the principles, the actual calculation is challenging due to various factors like air viscosity, compressibility, and turbulence. It mentions the use of wind tunnels and the Kutta condition in simplifying the approximation of lift. The paragraph also highlights the limitations of two-dimensional lift calculations and the need for empirical measurements to supplement theoretical predictions.

This section explores the concept of frame of reference in relation to airfoil dynamics, discussing how the speed of air moving past an airfoil can be perceived differently depending on the chosen frame of reference. It emphasizes that in the context of wind tunnel testing, the airfoil is considered stationary while the air moves around it, which is a cost-effective way to study aerodynamics.

This paragraph delves into the factors that affect lift, such as airfoil shape, wing size, and angle of attack. It discusses how changes in these factors can significantly impact the amount of lift generated. The paragraph also introduces the concept of the center of pressure and how its position can shift with changes in angle of attack, affecting the aircraft's maneuverability.

This section introduces the ground effect, explaining how proximity to the ground can temporarily reduce induced drag and allow for a lower speed takeoff. It also discusses the three axes of flight—longitudinal, lateral, and vertical—and how they relate to stability. The importance of maintaining stability during flight and the role of the aircraft's design in achieving this stability is highlighted.

This paragraph contrasts the stability of different types of aircraft, such as trainers like the Cessna 172, which are stable and self-righting, with aerobatic aircraft that are designed to be less stable for performing maneuvers. It touches on the importance of understanding aircraft stability when flying and how factors like the center of gravity and wing design can affect stability.

This section explains the concept of a stall, where the airflow over the wings separates due to a high angle of attack, leading to a loss of lift. It emphasizes that stalls can occur at any airspeed and power setting and are based on the angle of attack. The paragraph also introduces the concept of a spin, a dangerous and uncoordinated maneuver that can follow a stall if not managed correctly.

This paragraph discusses various factors that can cause an airplane to have a tendency to turn left, such as torque due to propeller rotation, the p-factor related to asymmetrical thrust, and the corkscrew effect from the spinning propeller's slipstream. It also touches on gyroscopic precession and its impact on flight control.

This section introduces the concept of blended wing body aircraft, which offer better aerodynamic efficiency and fuel consumption due to their design. However, it also addresses the challenges in adopting such designs, including the need for new infrastructure and the preferences of passengers and airlines for traditional aircraft designs.