Aerodynamics Flashcards
What are the four forces of aerodynamics?
- Thrust
- Drag
- Lift
- Weight
What is thrust in aerodynamics?
Forward force produced by the propeller
Define drag in the context of aerodynamics.
Rearward force caused by disruption of airflow
What is lift?
Upward force created by air acting on airfoils
What does weight refer to in aerodynamics?
Downward force caused by gravity
State Bernoulli’s principle.
Higher air velocity results in lower pressure
What is Newton’s third law?
Every action has an equal and opposite reaction
Describe the design of an airfoil.
Upper surface is longer than lower surface
What is the result of the airfoil design?
Creates higher pressure below, resulting in lift
Define angle of attack (AoA).
Angle between chord line and relative wind
What is the relationship between AoA and speed?
Greater AoA is needed at lower speeds
In steady flight, what is true about the forces?
All forces are balanced; opposite forces are equal
What is parasite drag?
Drag caused by wind moving around the aircraft
Define form drag.
Drag caused by wind moving around the aircraft
What is interference drag?
Drag caused by the intersection of wind streams at 90° angles
What causes skin friction drag?
Caused by any non-smooth surfaces on the aircraft
What is induced drag?
Byproduct of lift, altered by changing AoA
Describe wingtip vortices.
Moves out, up, in, around wing tips, then moves outward and down
When are wingtip vortices most prevalent?
In heavy, clean, slow aircraft
What is ground effect?
Interference of ground surface with airflow
What are the effects of ground effect?
- Breaks up vortices
- Increases performance
- Reduces drag
How do higher temperature and humidity affect density altitude?
Increase density altitude, decreasing performance
Higher temperature and humidity lead to a decrease in air density, which can adversely impact aircraft performance.
What is the CG in aviation?
Point where the plane would balance, if suspended
CG stands for Center of Gravity, a critical factor in aircraft stability and control.
What are the three axes of aircraft movement?
- Lateral - stabilator
- Longitudinal - ailerons
- Vertical - rudders
These axes define the orientation and movement of the aircraft in three-dimensional space.
What does ‘Moment’ measure in aviation?
Measures an aircraft’s tendency to rotate
Moment is calculated as the product of force applied and the distance at which it is applied.
How is Moment calculated?
Moment = weight X arm
The arm is the distance from the reference point to the applied force.
How is CG calculated?
CG = total moment / total weight
This formula helps determine the aircraft’s center of gravity based on its weight distribution.
What is Stability in aviation?
Ability of an aircraft to correct deviations after a disturbance
Stability is crucial for safe flight operation and handling.
What is Static stability?
Initial tendency back to equilibrium
Static stability refers to how an aircraft reacts immediately after a disturbance.
What is Dynamic stability?
Overall tendency after disturbance
Dynamic stability considers how the aircraft behaves over time after a disturbance.
What does Longitudinal stability refer to?
Quality of pitch stability
It assesses how well the aircraft maintains its pitch attitude.
What is Lateral stability?
Stability of roll
Lateral stability ensures the aircraft maintains its roll attitude during flight.
What does Directional stability refer to?
Yaw stability
It involves how well the aircraft maintains its directional path during flight.
What are the two components of lift in a turn?
- Vertical (upward)
- Horizontal (inward)
Understanding these components is essential for managing aircraft performance during turns.
What is a Coordinated turn?
Left turn, left rudder
A coordinated turn maintains balanced flight and prevents skidding.
What is a Slipping turn?
Left turn, right rudder
This type of turn can lead to a loss of control and should be avoided.
What is a Skidding turn?
Left turn, excessive left rudder (avoid)
Skidding turns can cause adverse yaw and loss of control.
In a turn, what must be increased to equalize total lift and total weight?
Angle of Attack (AoA)
Adjusting AoA is crucial for maintaining lift during turns.
What occurs during a climb when lift is initially greater than weight?
Aircraft will balance and airspeed decreases
This indicates a transition from a climb to a stable flight condition.
What causes stalls in aircraft?
Exceeding critical AoA
Stalls result in significant loss of lift, starting at the wing root and spreading to the wing tips.
What is the result of a stall combined with yaw?
Spin, uncoordinated stall
This situation can lead to a dangerous loss of control.
What condition is necessary for recovery from a stall to be achieved?
Being within CG envelope
Center of Gravity (CG) envelope is crucial for recovery.
What does the coefficient of lift (CL) describe?
Lift depending on atmospheric variables
CL is a key factor in understanding lift performance.
What is CLMax?
Maximum peak of CL at critical AoA
This is the highest lift coefficient before stall occurs.
What is the recovery procedure for a spin?
Full opposite rudder, elevator forward, aileron level, power idle
These steps help regain control of the aircraft during a spin.
What is torque reaction in relation to propeller forces?
Opposite force trying to go opposite direction of propeller spin
This creates a left turning tendency in the aircraft.
What is the corkscrew effect?
Spiraling slipstream around the plane causing left turn tendency
This effect is due to the rotation of the propeller.
What does gyroscopic action refer to?
Turning of a gyro in response to a deflective force, felt 90 degrees later
This can create either left or right turning tendencies.
What is P-factor in aviation?
Ascending blade is thinner than descending blade
This phenomenon also contributes to the left turning tendency of the aircraft.
What is the load factor in aviation?
Amount of force of the aircraft’s structure, measured in G’s
What is the limit load factor?
Highest load factor in normal operation, specified by category (normal, utility, acrobatic)
What causes the load factor to increase significantly?
Centrifugal force and weight; increases significantly after 60 degrees of bank
What happens if an aircraft is flying below maneuvering speed?
Aircraft will stall before it breaks
What is the reference datum in aviation?
Invisible vertical plane from which weight arms are measured
How are arms measured in relation to the center of gravity (CG)?
Arms forward of CG are negative, behind are positive
Who is responsible for weight and balance in aviation?
Pilot in command (PIC)
What constitutes standard empty weight?
Airframe + engine + unusable oil and fuel
What is the basic empty weight of an aircraft?
Standard empty weight + flight instruments
Define payload in aviation.
Occupants + baggage
What is useful load?
Pilots + passengers + baggage + usable oil/fuel
Fill in the blank: Zero fuel weight = Useful load - _______
Fuel
What does fuel load refer to?
Usable fuel
