A103 Aerodynamics Flashcards
Define Airfoil
Any surface, such as a wing, propeller, rudder, or even a trim tab, which provides
aerodynamic force when it interacts with a moving stream of air.
Leading Edge
The part of an airfoil that meets the airflow first.
Trailing Edge
The part of the airfoil where the airflow over the upper surface rejoins the
lower surface airflow.
Chord Line
An imaginary straight line drawn through an airfoil from the leading edge to the
trailing edge.
Camber
The camber of an airfoil is the characteristic curve of its upper and lower surfaces.
The upper camber is more pronounced, while the lower camber is comparatively flat. This causes
the velocity of the airflow immediately above the wing to be much higher than that below the wing.
4 Forces acting on a plane in flight
lift, weight, thrust, and drag
Explain Lift
The upward force created by the effect of airflow as it passes around a wing
Explain Weight
The force that opposes lift and is caused by the downward pull of gravity.
Explain Thrust
Created by the powerplant that propels the airplane forward through the air.
Explain Drag
The resistance of the atmosphere to the relative motion of an aircraft.
(Opposes thrust)
Explain Ground Effect
The interference of the surface of the earth with the airflow patterns about
the aircraft in flight. This alters the wing’s upwash, downwash, and wingtip vortices. Ground
effect reduces the induced drag proportionate to the distance of the aircraft above the ground.
Explain a stall
Separation of airflow and resulting loss of lift
due to the critical angle of attack being exceeded.
When the wing is below the critical angle of attack the
airflow smoothes out and the wing produces lift again.
An airplane wing stalls whenever the critical angle of
attack is exceeded. A stall can occur in any flight
attitude and at any airspeed.
Explain Stall Recovery
- Smoothly apply max allowable power
- Reduce angle of attack
- Roll towards wings-level
- Recover to level flight (avoid secondary stall)
- Adjust power as needed
“Max, Relax, Roll”
What causes a spin?
When both wings are stalled and there is a yawing moment due to uncoordinated
flight.
To prevent a spin, be sure correct rudder usage is applied during a stall.
Factors Affecting Lift
Bernoulli’s Principle
Newton’s 3rd Law
What is Bernoulli’s Principle?
The principle states that: “as the velocity of a
fluid or gas increases, its pressure decreases” (temp also drops).
What is the Newton’s 3rd law in relation to flight?
“For every action there is an equal and opposite reaction.” The reaction of the air striking the bottom of the wing is an upward or lifting force.
What is Angle of Attack?
The acute angle between the chord line of the airfoil and the direction of the relative wind.
Bottom line of AoA?
Faster you go, the less AoA you need.
Slower = more AoA
How are we controlling lift?
Change angle of attack
Change airspeed
Change shape of wing
2 types of drag
Parasite
Induced
What is Parasite drag?
Any A/C surface that interferes with the smooth
flow of air around airplane
3 Types of Parasite Drag?
Form
Interference
Skin Friction
Form Drag
Parasite drag from turbulent wake caused by airflow
around a structure
Depends on size and shape of structure
(A10 vs F16)
Interference Drag
- Parasite drag from interaction of varied currents that flow
over an airplane and mix together - Turbulence can be 50% to 200% greater when combined
than separate
(Antennas, stuff hanging from plane)
What is Skin Friction Drag?
- Parasite drag from roughness of airplane
surfaces - Rivet heads
- Irregularities (bugs / dirt)
What is Induced Drag?
- Drag as a result of the production of lift
- Increases with the increase in the angle of attack
- Caused by the spanwise airflow around the wing
- Varies inversely with the square of the airspeed
What is the L/D Max at 1764lbs?
73 KIAS
Glide ratio of DA20?
11:1 or 1.8nm for every 1,000 ft of altitude loss
When is Induced Drag Greatest?
When the A/C is heavy, slow, and clean
When is ground effect most prevalent?
One wingspan from the ground and lower
What causes a stall?
Exceeding the critical angle of attack
What happens to lift in a stall?
Drops off drastically and you can no longer maintain level flight.
What are the signs of an impending stall?
- Mushy feeling in flight controls and less control effectiveness
- Stall warning device – horn, buzzer, light
- Loss of R.P.M. in fixed pitch props
- Reduction in sound of air flow
- Buffeting and/or vibrations
What is the indication of a stall?
- Uncommanded pitch and/or roll movements
- Loss of control effectiveness
3 Types of Stalls?
Power-On
Power-Off
Accelerated Stall
What is a Power-Off Stall?
Simulates approach and landing conditions
What is a Power-On Stall?
- Simulates takeoff, climb-out, go-around conditions
What is Accelerated Stall?
- Practiced to understand how stalls can occur at
higher airspeeds and load factors (not
accomplished at IFT)
Spin Recovery (Memory Item)
1.THROTTLE……… IDLE
2. RUDDER …..FULL (OPPOSITE SPIN DIRECTION)
3. CONTROL STICK…..EASE FORWARD
4. RUDDER ……NEUTRAL WHEN ROTATION STOPS
5. FLAPS ………….CRUISE
6. CONTROL STICK…… PULL CAUTIOUSLY
CAUTION: Recover to level flight cautiously to avoid inducing a secondary
stall, but do not allow the airspeed to exceed 164 KIAS.
What is the Center of Gravity?
- Common point for all three axes
- Where weight of airplane is concentrated
- Airplane moves about this point in all three directions
3 Controls that cause rotation about the 3 axes?
- Ailerons, elevator, rudder cause rotation about the three axes
3 Axes?
Longitudinal, Vertical, Lateral
What controls the Longitudinal/Roll Axis?
Ailerons
What causes an aircraft to turn in flight?
Horizontal Component of Lift
What controls the Lateral/Pitch Axis?
Elevator
What controls the Vertical/Yaw axis?
Rudder
What is the definition of Load Factor?
- Ratio of:
Load supported by the wings
to
Actual weight of the aircraft and contents
What is Maneuvering speed?
Max speed at which
you can use full,
abrupt control
movement without
over stressing the
airframe
What are the 4 Turning Tendencies?
- Torque
- Gyroscopic precession
- Asymmetrical thrust
- Spiraling slipstream
Note: These are most often noticeable at high power settings & low
airspeed situations.
What is Torque Turning Tendency?
Propeller rotates clockwise – causes torque which
tends to rotate airplane counterclockwise about
longitudinal axis
What is Gyroscopic Precession (turning Tend)
- Precession is resultant reaction
when force applied to rim of
rotating disk - In a nose gear aircraft, tendency on takeoff and landing flare is a yaw to the RIGHT
Asymmetrical Thrust (P-factor)?
- Airplane flown at high power and high angle of attack
- Uneven angles of
attack between ascending and descending blades - Unequal thrust causes yaw to left
Spiraling Slipstream?
- Slipstream from
propeller wraps around
fuselage and hits left
side of vertical fin - Causes tail to move
right – nose to yaw left
