Angle of attack

Airfoil angle of attack

MISB ST 0601.8 - Platform Angle of Attack

Coefficients of Drag and Lift vs AOA

Lift curve

Su-35 (12509727094)

Angle of Attack (AoA, α) is a fundamental concept in aerodynamics that describes the angle between the chord line of an airfoil and the oncoming air (or relative wind). It plays a critical role in the generation of lift, which is essential for the flight of aircraft. Understanding and controlling the angle of attack is vital for safe and efficient aircraft operation, as it affects the lift, drag, and stall characteristics of the airfoil.

Definition

The angle of attack is defined as the angle between the chord line of an airfoil and the direction of the oncoming air. The chord line is an imaginary straight line connecting the leading and trailing edges of the airfoil. The angle of attack is positive when the leading edge of the airfoil is above the direction of the oncoming air.

Importance in Flight

The angle of attack is a key parameter in determining the lift generated by an airfoil. As the angle of attack increases, the lift generated by the airfoil also increases, up to a point. Beyond this point, further increases in the angle of attack lead to a decrease in lift and an increase in drag, eventually resulting in a stall. A stall occurs when the airflow over the airfoil becomes turbulent and separated, leading to a rapid loss of lift.

Control and Measurement

Pilots control the angle of attack through the aircraft's control surfaces, such as the elevator and flaps, to maintain the desired flight path and performance. In modern aircraft, angle of attack indicators or sensors are often used to provide real-time data to the pilot, helping to avoid critical angles that could lead to a stall.

Critical Angle of Attack

The critical angle of attack is the angle at which an airfoil produces the maximum lift coefficient. Beyond this angle, the airfoil enters a stall condition. The critical angle of attack is a fixed characteristic of the airfoil and does not change with flight conditions. However, the actual angle of attack at which a stall occurs can vary with factors such as weight, speed, and aircraft configuration.

Applications and Considerations

Understanding and managing the angle of attack is crucial not only in fixed-wing aircraft but also in helicopters, wind turbines, and other aerodynamic devices. In the design of airfoils and aircraft, engineers must consider the effects of angle of attack on lift, drag, and stall characteristics to ensure safety and performance.

See Also

• Lift (force)
• Drag (physics)
• Stall (fluid mechanics)
• Airfoil
• Aerodynamics