Aerodynamics Flashcards
Define Vector
A Vector is a quantity that represents magnitude and direction. Can be divided into separate components- vertical and horizontal
Define: Air Density
Mass per unit volume. Air density is air particles within a given volume
Define: moment
A moment is a rotational force around a point or axis
State the requirements for an airplane to be in equilibrium flight
Equilibrium exists when the sum of all forces and the sum of the moments around the center of gravity equals zero
Define relative wind
relative wind is the airflow experienced by the aircraft as it flies through the air. It is always equal and opposite to the flight path. The relative wind may arise from the motion of the body, motion of the air, or from both
State the requirements for an airplane to be in trimmed flight
Trimmed flight is a condition that exists when the sum of the moments acting around the center of gravity are equal to zero
Describe the relationship between temperature and altitude
Temperature drops 2C per 1000’ gained in altitude
State the General Gas Law
Explain the continuity equation given cross-sectional area and velocity
A1V1 = A2V2
Explain:
Indicated Air Speed
IAS
PT= PS + q
Calibrated airspeed
CAS is IAS corrected for position/instrument error
Equivalent airspeed
EAS is CAS corrected for compressibility effects
This is only used when flying at supersonic speeds
True Airspeed
TAS is EAS corrected for density
Ground Speed
Ground speed is TAS Corrected for wind
Mean Camber Line
Line from leading edge to trailing edge, halfway between upper and lower surface of the airfoil
Define Chord
Chord is the precise measurement between the leading and trailing edges
Define Camber and camber types
Camber: maximum distance between the mean camber line and the chordline, measured perpendicular to the chordline
Define: wingspan
wingspan is measured tip to tip
Define: wing area
Wing area is
the apparent surface area of a wing from tip to tip including the area within the fuselage, hull, or nacelles
Define: chordwise airflow
Chordwise airflow: airflowing at right angles to the LE
only air flow that accelerates over the wing and the only type of airflow that produces lift
Define: spanwise airflow
spanwise airflow:
airflow that travels along the span of the wing parallel to the leading edge.
normally root to tip
DOES NOT PRODUCE LIFT
Define: pitch attitude
angle between the airplane’s longitudinal axis and the horizon
Define: flight path
flight path is the path described by the center of gravity as it moves through an air mass
Define: Relative Wind
relative wind is the airflow the airplane experiences as it moves through the air. It is equal in magnitude and opposite in direction to the flight path
Define: Angle of Attack
AOA is the angle between the relative wind and the chordline of an airfoil
Define: Angle of Incidence
AOI is the angle between the longitudinal axis of the airplane and the chordline of the wing
Define the Center of Gravity
CG is the point at which all weight is considered to be concentrated and about which all forces and moments are measured
Define the Aerodynamic Center
Aerodynamic center is the point along the chordline around which all changes in the aerodynamic force take place.
located about 25% of the length of the chordline from the leading edge. It is also the point of maximum thickness of the airfoil or where we have the most positive camber
What are the components of CL
Components that make up the coefficient of lift are:
compressibility
Aspect Ratio
Viscosity
AOA
Camber
*the shape of the airfoil and the AOA are the only 2 which can be controlled by the pilot
Define CLMAX
CLMAX is the maximum lift coefficient. It is dependent on the AOA. The CLMAX will be the most effective angle of attack
Define: Parasite Drag
Drag that is not associated with lift.
2 kinds:
Form: results from the disruption of streamline flow (shape and velocity important factors)
(think of an eddy- the laminar airflow separation from the surface creates a low pressure wake behind the object which pulls the object backward and slows down forward motion)
Friction: any drag caused by the surface of the object itself
minimize with streamlining and clean, well kept, smooth surfaces
Dp = q f where f= the equivalent parasite area (or the size of a flat plate which would generate the same amount of drag)
Define: Induced drag
Induced drag IS associated with the production of lift
comes from the rotated total lift due to the change in the relative wind produced by the wingtip vortices (extra downwash)
*its the horizontal component of the Rotated Total Lift vector
Describe factors affecting induced drag
Induced drag is affected by angle of attack and airspeed.
the slower the speed, the greater the AOA is needed to produce lift. With greater AOA, you end up with more lateral movement of air to the wingtip creating greater wingtip vortices which will increase the downwash. The increased downwash will further recline the total lift vector creating increased Di
Higher velocity, lower drag
List prevention methods of induced drag
Prevention of induced drag:
ground effect
wingtip devices
What is L/DMAX
L/DMAX is the point at which the parasite and induced drag are equal creating minimum total drag
this is your most efficient angle of attack (Max range)
L/D Max is the point where the ratio of lift to drag is the greatest
Define: Boundary Layer
Boundary layer-
Thin layer of airflow over an airfoil that consists of laminar and turbulent flow
laminar flow: moves smoothly with little friction
turbulent: disorganized with large amounts of friction
Define: Stall
A stall is a condition of flight in which an increase in AOA will result in a decrease in CL.
happens at AOAs greater than the CLMAXAOA
Describe the factors necessary for an airplane to spin
spins happen with uncoordinated stalls (stall + yaw)
inside wing has a higher AOA and CD than the outside wing
therefore, the inside wing (aka downgoing wing) has lower CL and does not produce lift
Describe the actions necessary to recover from a spin
To recover from a spin (PARE)
Power to idle
Neutralize Ailerons
Opposite Rudder
Forward Elevator to break stall
Define: maximum angle of climb
AOC is maximizing altitude while minimizing distance traveled
useful to clear obstacles
Define: maximum rate of climb
ROC is maximizing altitude while minimizing time
Get to an altitude as quickly as possible
Define maximum range
Max range- maximum distance traveled for a given amount of fuel
Define Maximum endurance
Max endurance:
maximum time airborne for a given amount of fuel
occurs at the bottom of the power curve
higher altitudes have better engine performance which decreases the amount of fuel needed
Define: max glide range
Max glide range:
max distance traveled in a glide
the minimum angle of descent occurs at L/DMAX
Define: maximum glide endurance
Max glide endurance
minimum RATE of descent occurs at the bottom of the power curve
What are the regions of normal and reverse command on the power curve
Normal Command: occurs to the right of Max END on a power curve
Reverse command: to the left of Max END on the power curve
flying slower than the max endurance you need to increase power
Describe a slipping turn
Slipping turn:
Nose is outside of the turn
increased radius
decreased rate
ball is same side of turn needle
Describe a skidding turn
Skidding turn:
nose is inside
decreased radius
increased rate
ball is opposite of turn needle
dangerous!
what is P-factor?
what is slipstream swirl?
how does the pilot compensate?
P-Factor: yawing moment caused by one side of the prop
slipstream swirl: the corkscrew airflow traveling around the fuselage and impacting the left side of the vertical stab
greatest at low airspeeds and high power settings
both cause the nose to yaw left so use your right rudder to compensate
Define: limit load
limit load
max load factor anticipated in normal operation and that can be sustained without risk of permanent deformation
Define: ultimate load
Ultimate load:
maximum load factor that can be sustained without structural failure and is 1.5x the limit load
Define: wind shear
Wind shear is a suddent change in wind direction and/or speed over a short distance
What is the difference in speed between a power on stall and power off stall?
A power on stall still has some component of lift to offset the weight of the airplane. Therefore, stall speeds will be lower in a power on stall
What is the Max Endurance on the power curve?
Max endurance on the power curve is the max amount of time that the airplane can remain airborne on a given amount of fuel. This is the lowest point on the power curve.
Where is the highest AOA located on the power curve
The higest AOA is located to the left side of the power curve
What is the relationship between velocity and throttle (power) in the region of normal comand?
In the region of normal command: to increase velocity you must increase the power
the inverse is true for the region of reverse command
what is the equation for distance for take off
what is the equation for take off velocity?
what is the recovery for a stall?
Relax- relax back pressure slightly to decrease AOA and level plane (bring nose down)
Max- smoothly advance throttle to full power
Level- level wings to the horizon
Ball- apply rudder as necessary (usually Right rudder) to center the ball
