A plane’s angle of attack is the angle between its airfoil’s chords and airflow. Lift and drag both increase with an increasing angle of attack until the critical angle of attack is reached.
The critical angle of attack is when an aircraft experiences maximum lift. A plane stops generating lift and stalls if its angle of attack increases above its critical angle of attack.
Other important angles in aviation include pitch angle and angle of flight.
The pitch angle is the angle between the plane’s airfoils and the flat ground. The angle of flight is the angle between a plane’s velocity vector and either the horizon or flat ground.
The Angle of Attack is important in aviation because it informs pilots how much lift their aircraft experiences.
Both lift and drag increase with an increasing angle of attack until a certain limit called the critical angle of attack is reached.
A plane stalls if its angle of attack exceeds its critical angle of attack.
So, pilots need to monitor their angle of attack to ensure they don’t cross their critical angle of attack.
If a pilot crosses their aircraft’s critical angle of attack, the aircraft won’t experience any more lift and will begin to descend.
How the Angle of Attack Affects Flight
The angle of attack affects flight in several ways.
The angle of attack informs a pilot of what lift and drag their aircraft is experiencing.
The higher the angle of attack, the higher the lift and drag forces on the aircraft.
Conversely, lift and drag are lower when the angle of attack is lower.
A plane maximizes lift at its critical angle of attack, but experiences stalling if it crosses the critical angle of attack.
A plane loses all lift when it stalls and begins to descend.
So, simply put, the angle of attack is so important to understand because if the critical angle of attack is reached and then exceeded, it will cause an aircraft to lose lift and fall from the sky.
Inevitably, pilots need to avoid exceeding their critical angle of attack.
How Angle of Attack is Measured
Angle of attack is usually measured with a free movement vane that’s attached to either the aircraft’s fuselage or on a wing-mounted boom.
The vane is aligned with airflow, and the sensor inside it calculates the angle of attack, which is relayed to the pilot.
An alternative approach is using pressure-based probes that have multiple ports.
The port pressure difference is then used to calculate the aircraft’s angle of attack.
How to Calculate the Angle of Attack
The formula for calculating angle of attack is as follows:
CL = CLα (α-αL=0)
CL is the Lift Coefficient
CLα is the Lift curve Slope.
α is the Angle of Attack
αL=0 is the Zero lift angle
What the Critical Angle of Attack Means
Lift and drag both increase with an increasing angle of attack until a certain point known as the critical angle of attack is reached.
A plane’s lift is maximized at its critical angle of attack. If a plane increases its angle of attack beyond its critical angle of attack, it will reduce its lift and stall. When a plane stalls, it can no longer maintain forward flight and descends from the sky.
So, a critical angle of attack is the maximum safe angle of attack for an aircraft.
Increasing an aircraft’s angle of attack beyond its critical angle of attack is unsafe since it causes the plane to stall.
Difference Between Angle of Attack and Pitch Angle
The Pitch Angle is the angle between an airfoil’s chord and the flat surface, while the angle of attack is the angle between the airfoil’s chord and airflow. So, the pitch angle helps define the aircraft’s position relative to the Earth’s surface.
In contrast, the angle of attack indicates an aircraft’s direction relative to wind flow.
Both angles are only equal on an aircraft if the air approaches the aircraft horizontally to the Earth’s surface.
Difference Between Angle of Attack and Flight Path Angle
Flight path angle is the angle between a plane’s velocity vector for a flight and a fixed flat surface, usually either the flat ground or the horizon.
In contrast, the angle of attack is the angle between a plane’s airfoil chords and airflow.
An aircraft’s flight path angle is positive when the plane tilts upwards or ascends from the horizon, and it’s negative when the plane tilts downwards or descends from the horizon.
The flight path angle helps identify the plane’s direction of movement relative to the horizon or flat ground.
Meanwhile, the plane’s angle of attack informs the pilot how much lift and drag the aircraft experiences and the direction of its wings relative to the airflow.
In conclusion:
A plane’s angle of attack is the angle between its airfoil chords and outside airflow.
A plane’s angle of attack matters because it indicates how much lift and drag the plane experiences.
Lift and drag both increase with an increasing angle of attack.
A critical angle of attack is the angle of attack at which a plane experiences maximum lift and would begin to stall if the angle of attack increases beyond this point.
In contrast, an aircraft’s pitch angle is the angle between its airfoil’s chords and the flat surface, while a flight path angle is the angle between a plane’s velocity vector and flat ground.
Helen Krasner holds a PPL(A), with 15 years experience flying fixed-wing aircraft; a PPL(H), with 13 years experience flying helicopters; and a CPL(H), Helicopter Instructor Rating, with 12 years working as a helicopter instructor.
Helen is an accomplished aviation writer with 12 years of experience, having authored several books and published numerous articles while also serving as the Editor of the BWPA (British Women Pilots Association) newsletter, with her excellent work having been recognized with her nomination of the “Aviation Journalist of the Year” award.
Helen has won the “Dawn to Dusk” International Flying Competition, along with the best all-female competitors, three times with her copilot.
