Final Exam Review Flashcards
What effects lift? (think the lift equation)
Air Density (p)
AOA + Airfoil shape (Coefficient of lift)
Wing Planform Area (S)
What is the Boundary Layer? What are its 3 section?
- Layer of air over surface that show local retardation due to viscosity
1. Laminar (fluid particles don’t intermingle, easily separates from airfoil)
2. Transition (laminar flow is disturbed)
3. Turbulent (cross-streamlines, aerodynamically dead, wants to stick to the airfoil)
What CAUSES the boundary layer? What makes it disappear?
- Viscous effects
- Disappears with ADVERSE PRESSURE GRADIENT…flow slows to point of reversal and boundary layer separation
Induced drag is determined by ____ and increases/decreases with:
Lift!
- Increases with higher weight and altitude
- Decreases with lower airspeed
Form/Pressure drag is determined by ____ and increases with:
Shape/size!
- Increases with boundary layer separation aft center of lift
What CAUSES form/pressure drag?
- Pressure differences between forward and aft surfaces (greater out front, lower out back)
What CAUSES parasite drag?
- The deflection/change in direction of air
Parasite drag increases with:
- Increases with airspeed
What is profile drag? What CAUSES it?
Skin friction + form drag
- A type fo parasite drag
- Causes by urface irregularities
If you streamline and object, what happens to profile drag?
IT REMAINS THE SAME!!
True or False: Total drag is constant.
FALSE!
What CAUSES interference drag?
- The intersection of 2 bodies or boundary layers
When is interference drag worst? WHERE is it most critical?
- Worse at ACUTE angles
- More critical on UPPER portion of wing due to increased flow speeds
What is thrust? What does it do for the a/c and how is it affected by velocity?
- A mechanical force
- Force that moves the a/c forward and overcomes drag
- Thrust decreases as velocity increases
What are the 3 main types of airfoils we learned about?
- Stationary Cylinders
- Rotating cylinders
- Symmetrical
What are 2 main aspects related to Rotating Cylinder airfoils?
- Viscous
2. Magnus Effect
What is Magnus Effect? Explain the concept.
- Aspect of a rotating cylindrical airfoil due to a force being exherted, and acceleration of the force occuring
- A resultant force
- Net lift
What are 2 main aspects related to Stationary Cylinder airfoils?
- Non-Viscous
2. Streamlining
What is streamlining? Explain the concept.
- Literally smoothing out the edges on an airfoil to create smooth, undisturbed airflow
- Forward/aft stagnation point
- Diverging airflow
What are 3 main aspects related to Symmetrical airfoils?
- Stagnation point
- Diverging airflow
- Center of Lift = Max thickness point
What exactly is L/D? What are its limitations?
- An AOA
- The best glide angle
- NOTHING changes this…airspeed will change, but AOA will not
What speed does L/D represent?
- None, L/D is NOT an airspeed
- L/D is an AOA!
Where does Relative Wind hit the propeller? How does this change with velocity, and why? (draw pic)
- Relative wind ALWAYS hits the back of the prop.
- Stationary: RW is straight down for prop
- In motion: RW is pushed closer to prop chord line making a more acute angle
- The faster you go, the more you reduce your AOA bc RW moves forward
If Lift is DOUBLED, how is Induced Drag affected?
Induced drag increases by 4 times (4x greater)
Your airplane goes 50 knots with a 10hp engine, and we want to go 100 knots. How powerful of an engine do we need to be able to achieve this?
- We want to double our velocity (2x)
2^3 = 8 - We want an engine that can achieve that velocity
10hp x 8 = 80hp
Newton’s 1st law states:
Forces in motion tend to stay in motion unless they are acted on by an opposing force (gravity is unbalanced)
Newton’s 2nd law states:
Acceleration of an object is directly proportional to the net force, in the same direction (acceleration and force go in the same direction)
- Force = Mass x Acceleration
Newton’s 3rd law states:
For every action there is an equal and opposite reaction (differences in mass = unbalanced acceleration)
What is Energy?
- The ability to do work
- Pressure in a given volume
5 different forms (potential and kinetic)
What is the equation for Work?
Work = Force x Distance
____ static lead to ALL dynamic.
Positive Static leads to ALL dynamic!
___ stability is the INITIAL tendency of an object
Static
___ stability is the tendency of an object OVER TIME
Dynamic
___ stability is given by CG and the Horizontal Stabilizer
LONGITUDINAL stability
___ stability is given by Dihedral, Keel Effect and Sweepback wings
LATERAL stability
___ stability is given by the vertical tail (fin and rudder)
VERTICAL stability
What atmospheric conditions result in LOW DENSITY? (think temp, humidity and pressure)
- High temps
- High humidity
- Low pressure
How does Low Density affect a/c performance?
Poor a/c performance
True or False: DYNAMIC stability = STATIC stability.
TRUE! But this is not always true the other way around
What are the 3 main forces during Takeoff?
- Thrust (decreases with velocity)
- Drag (parasite and induced)
- Friction (decreases with velocity)
Liftoff speed is usually:
- 20% greater than stall speed
- 1.2Vso
Explain Vy
- Best RATE
- ASI giving greatest gain in altitude in the shortest TIME
Explain Vx
- Best ANGLE
- ASI giving greatest gain in altitude shortest HORIZONTAL DISTANCE over the ground
True or False: The VSI will read the SAME at both Vx and Vy
TRUE! This is because they are complimentary angles
What are flaps? What do they do for us, and how?
- High lift devices
- Gives the SAME LIFT at LOWER AIRSPEEDS (lift does NOT increase)
- Flaps change the airflow/slipstream that hits the tail
What are the 5 force vectors acting on an a/c? Draw a picture and label.
- Lift
- Thrust
- Weight (fwrd of lift)
- Tail
- Drag
What 2 things give us Airspeed?
- Forward acting weight
2. Forward acting lift
What makes Total Drag more to the RIGHT?
Altitude
What makes Total Drag more to UP?
Gear DOWN or heavier weight
What makes Total Drag more to DOWN?
Gear UP or light weight
As speed increases, what drag goes up? What drag goes down?
- Parasite drag increases
- Induced drag decreases
What are the 4 forces the Tail Down Force must equal in level flight?
- Pendulum Affect
- Fuselage Destabilizing
- Lift-Weight/CG Coupling
- Wing pressure differential
8 ways to reduce landing distance AFTER TOUCHDOWN:
- Aerodynamic braking
- Wheel braking
- Thrust reversers
- Spoilers
- Retract flaps
- Land into wind
- Uphill
- Dry Runway
Ways to reduce landing distance DURING APPROACH:
- Slow airspeed
- Flaps
- Steeper AOA
- Idle power
Tail down = 315lbs negative stability Wing = 45lbs positive stability Fuselage = 155lbs positive stability Thrust line = 40lbs positive stability - How much is the lift/weight coupling producing?
40 - 315 - (155 - 45)
Pivotal Altitude equation?
GS^2/11.3 + Elevation
4 phases of a spin and descriptions
- Entry - Forces applies
- Incipient - First 2 turns, forces unbalanced
- Fully Developed - Forces reach equilibrium
- Recovery - Corrective forces applied by
Why do we hold ailerons neutral in spin recovery?
- Aileron inputs AGAINST the spin would create INDUCED DRAG on inside wing
- Aileron inputs WITH the spin would create LIFT on outside wing
In what situations are you most likely to enter a spin?
Low airspeed and high AOAs (traffic pattern)
Are both wings stalled in a spin? Is lift being produced?
Yes and yes!
What 4 things affect stall speed?
- Weight
- Load Factor
- Density
- CG Location
What is Va?
- Maneuvering speed where abrupt control movements can be made, and the a/c will STALL before structural damage can occur
- Cruise in gusty conditions
What force on a turning a/c acts opposite and parallel from the horizontal component of lift?
Centrifugal force! (acts inward)
