Aerodynamics Flashcards
What are the four forces acting on an aircraft?
Lift, Weight, Thrust, and Drag
These fundamental forces govern all flight. Lift opposes weight, thrust opposes drag. In unaccelerated flight, these forces are in equilibrium. Understanding their relationship is crucial for understanding basic aircraft performance.
What is angle of attack (AoA) in simple terms?
The difference between where the airplane is pointed (pitch) and where it’s actually going (flight path)
While technically it’s the angle between the chord line and relative wind, this practical definition helps pilots visualize and understand AoA. High AoA situations often precede stalls, making this understanding critical for safety.
What causes a wing to stall?
Exceeding the critical angle of attack (approximately 15° in a Cessna 172), causing airflow separation from the wing’s surface
A stall can occur at ANY airspeed or attitude - it’s all about angle of attack. When the critical angle is exceeded, the smooth airflow over the wing breaks away, resulting in a sudden loss of lift.
What are the four left-turning tendencies?
Torque, P-factor, Gyroscopic Precession, and Spiraling Slipstream
These four effects combine to create a left-turning tendency, most pronounced at high power and high angles of attack. They’re countered primarily with right rudder input, especially during takeoff.
How do flaps affect an aircraft’s performance?
They reduce stall speed and increase drag, allowing for steeper approaches and slower landing speeds
Flaps effectively change the wing’s shape to produce more lift at slower speeds. However, they also increase drag significantly, which is why they’re typically only used for takeoff and landing.
What are the two types of drag and how do they differ?
Parasite drag increases with speed, while induced drag increases as speed decreases
Parasite drag comes from air resistance against the aircraft (like a hand out a car window). Induced drag is a byproduct of lift production and increases at lower speeds when higher angles of attack are needed.
What is adverse yaw and how is it corrected?
The tendency of an aircraft to yaw opposite to the direction of roll, corrected by applying coordinated rudder
When ailerons are deflected, the down aileron creates more drag than the up aileron, causing the aircraft’s nose to yaw in the opposite direction of the turn. Proper rudder input coordinates the turn.
Why do turns increase stall speed?
Because more lift is needed to maintain altitude in a turn, requiring a higher angle of attack at the same airspeed
In a turn, the lift vector is tilted, requiring more total lift to maintain altitude. This means operating at a higher angle of attack, bringing you closer to the critical (stalling) angle.
What is the primary control used to adjust angle of attack?
The elevator
The elevator controls pitch, which allows the pilot to adjust the angle of attack. This is the primary way pilots control airspeed and maintain altitude or establish climbs and descents.
What is wake turbulence and when is it most dangerous?
Rotating vortices of air created by wing lift; most dangerous during takeoff and landing behind heavy aircraft
Wake turbulence is created by the pressure differential between the top and bottom of wings. It’s particularly dangerous during takeoff and landing due to proximity to the ground and operation at high angles of attack.
What is the relationship between lift and weight in unaccelerated flight?
They are equal
In unaccelerated flight (constant speed and direction), lift is approximately equal to weight. A common misconception is that lift must exceed weight to maintain altitude - this is only true when accelerating upward.
