Api Aerodynamics Eos

Front 1

Scalar quantity

Back 1

represents only magnitude, e.g. time, temperature, or volume

Front 2

• Vector

Back 2

represents magnitude and direction. Used to represent displacement, velocity, acceleration, or force

Front 3

• Force

Back 3

push or pull exerted on a body. Force = mass x acceleration.

F=ma

Front 4

• Mass

Back 4

quantity of molecular material that comprises an object

Front 5

• Volume

Back 5

amount of space occupied by an object

Front 6

• Density

Back 6

mass per unit volume. ρ=(mass/volume)

Front 7

• Weight

Back 7

force with which a mass is attracted toward the center of earth by gravity. g = 32.174 ft/s2

Front 8

• Moment

Back 8

vector quantity equal to a force (F) times the distance (d) from the point of rotation that is perpendicular to the force. M=F∙d

Front 9

• Work

Back 9

scalar quantity equal to the force (F) times the distance of displacement(s). W=F∙s

Front 10

• Power (P)

Back 10

rate of doing work or work done per unit of time

Front 11

• Energy

Back 11

scalar measure of a body’s capacity to do work. 2 types. Energy cannot be created or destroyed, but transformed from one form to another. Principle is called Conservation of Energy. Total energy equation is:
TE = KE + PE

Front 12

• Potential Energy

Back 12

ability of a body to do work because of its position or state of being. PE=weight∙height=mgh

Front 13

• Kinetic Energy

Back 13

ability of a body to do work because of its motion.
KE=½mV2

Front 14

• 1st law of equilibrium

Back 14

body at rest tends to remain at rest and a body in motion tends to remain in motion in a straight line at a constant velocity unless acted upon by some unbalanced force.

Front 15

• 2nd law of acceleration

Back 15

an unbalanced force acting on a body produces an acceleration (a) in the direction of the force that is directly proportional to the force and inversely proportional to the mass (m) of the body.
a = F/m or a = (Vout – Vin)/time

Front 16

• 3rd law of interaction-

Back 16

for every action, there is an equal and opposite reaction.
ex. thrust produced in a jet engine.

Front 17

• Equilibrium

Back 17

is the absence of acceleration, either linear or angular. Equilibrium exists when the sum of all the forces and the sum of all moments around the center of gravity equal zero.

Front 18

• Trimmed flight

Back 18

exists when the sum of the moments around the center of gravity is zero.

Front 19

Contrast Equilibrium and Trimmed Flight

Back 19

• In trimmed flight, the sum of the forces may not be equal to zero since you can trim an airplane into a turn. If you are in equilibrium flight, then you are in trimmed flight, but the reverse is not necessarily true.

Front 20

• Static pressure- (Ps)

Back 20

pressure each air particle exerts on another. Force acts perpendicular t any surface that the air particles collide with. Static pressure decreases with an increase in altitude at a rate of 1.0 in-Hg per 1000 ft.

Front 21

• Air Density- (ρ)

Back 21

total mass of air particles per unit volume. Air density decreases with an increase in altitude

Front 22

• Temperature- (T)

Back 22

measure of the average kinetic energy of the air particles

Front 23

• Average Lapse Rate

Back 23

temp decrease linearly with an increase in altitude at a rate of 2°C (3.57°F) per 1000 ft until 36,000 ft.

Front 24

• Humidity

Back 24

amount of water vapor in the air. As humidity increases, air density decreases.

Front 25

• Viscosity (μ)

Back 25

measure of the air’s resistance to flow and shearing. Air viscosity can be demonstrated by its tendency to stick to a surface. Air viscosity increases with an increase in temperature.

Front 26

• Local Speed of Sound-

Back 26

rate at which sound waves travel through a particular air mass. Dependant only on temperature. As the temperature of the air increases, the speed of sound increases.

Front 27

State the relationship between humidity and air density.

Back 27

Air viscosity increases with an increase in temperature.

Front 28

State the relationship between temperature and local speed of sound

Back 28

As temperature increases, the speed of sound increases.

Front 29

State the pressure, temperature, lapse rate, and air density at sea level in the standard atmosphere using both Metric and English units of measurement.

Back 29

English Metric
Static Pressure Pso |29.92 in-Hg | 1013.2 mb
Temperature To | 59°F | 15°C
Average Lapse Rate | 3.57°F / 1000 ft |2°C / 1000 ft
Air Density ρo | 0.002378 slugs / ft3 | 1.2255 gram / liter
Local Speed of Sound LSOSo | 661.7 kts | 340.4 m/s

Front 30

State the relationships between altitude and temperature, pressure, air density, and local speed of sound within the standard atmosphere.

Back 30

Temperature, pressure, air density, and local speed of sound all decrease with an increase in altitude within the standard atmosphere.

Front 31

State the relationships between pressure, temperature, and air density using the General Gas Law.

Back 31

Pressure (P), Density (ρ), Temperature (T), Universal Gas Constant (R)
P = ρRT

Front 32

• Aircraft

Back 32

any device used or intended to be used for flight in the air. (Balloon, dirigible, airplane, glider, helicopter)

Front 33

• Airplane

Back 33

is a heavier than air fixed wing aircraft that is driven by an engine and is supported by the dynamic reaction of airflow over its wings. (T-34 or T-37)

Front 34

compare, and contrast an aircraft and an airplane.

Back 34

Aircraft is used to describe a broad range of flying machines and Airplane describes more specific flying machines.

Front 35

List and describe the 3 major control surfaces of an airplane.

Back 35

•Ailerons- (and spoilers) are control surfaces that control roll.
•Rudder- upright control surface attached to vertical stabilizer to control yaw.
•Elevators- horizontal control surface attached to the horizontal stabilizer to control pitch

Front 36

List and define the 5 major components of an airplane.

Back 36

•Fuselage- basic structure of airplane.
•Wing- produce lift.
•Empennage- provides greatest stabilizing influence of all components of an airplane. Consists of aft part of fuselage, Vertical and Horizontal stabilizer.
•Landing Gear- ground taxi, absorb shock of takeoff and landings.
•Engine- provides thrust necessary for flight.

Front 37

List and define the components of the airplane reference system.

Back 37

•Center of Gravity (CG)- point at which all weight is considered t be concentrated, and about which all forces and moments (yaw, pitch ,and roll) are measured.
•Longitudinal Axis- passes from nose to tail of airplane.
•Lateral Axis- wingtip to wingtip.
•Vertical Axis- passes vertically through the center of gravity

Front 38

Describe the orientation between the components of the airplane reference system.

Back 38

An airplane reference system consists of 3 mutually perpendicular lines (axes) intersecting at the center of gravity.

Front 39

List and define the motions that occur around the airplane center of gravity.

Back 39

•Roll or Lateral Control- movement of lateral axis around the longitudinal axis.
•Pitch or Longitudinal Control- movement of the longitudinal axis around the lateral axis.
•Yaw or Directional Control- movement of longitudinal axis around the vertical axis.

Front 40

• Wingspan (b)

Back 40

length of wing from wing tip to wing tip.

Front 41

• Chord line-

Back 41

an infinitely long, straight line drawn through the leading and trailing edges of an airfoil

Front 42

• Chord

Back 42

Measure of the width of the wing or other control surface. Measured along the chordline from leading edge to trailing edge.

Front 43

• Tip Chord (CT)-

Back 43

measured at wing tip

Front 44

• Root Chord (CR)-

Back 44

chord at wing centerline.

Front 45

• Average Chord (c)

Back 45

average of every chord from the wing root to wing tip.

Front 46

• Wing Area (S)

Back 46

apparent surface area of a wing from wingtip to wingtip.
S = b∙c

Front 47

• Taper

Back 47

reduction in the chord of an airfoil from root to tip. The wings of the T-34 and T-37 are tapered to reduce weight, improve structural stiffness, and reduce wingtip vortices.

Front 48

• Taper Ratio (λ)

Back 48

ratio of the tip chord to the root chord.
λ = CT / CR

Front 49

• Sweep Angle (Λ)

Back 49

angle between a line drawn 25% aft of the leading edge and parallel to the lateral axis

Front 50

• Aspect Ratio (AR)

Back 50

ratio of wingspan to the average wing chord. High aspect ratio- glider. Low aspect ratio- fighter plane.
AR = b/c

Front 51

• Wing loading (WL)

Back 51

ratio of an airplane’s weight to the surface area of its wing. There tends to be an inverse relationship between aspect ratio and wing loading.
WL = (aircraft weight / wing area)

Front 52

• Angle of Incidence

Back 52

angle between the airplane’s longitudinal axis and the chordline of its wing.

Front 53

• Dihedral angle

Back 53

angle between the spanwise inclination of the wing and the lateral axis. The T-34 and T-37 both have dihedral wings to improve lateral stability.

Front 54

Describe and state the advantages of the semi-monocoque fuselage construction.

Back 54

Modified version of monocoque having skin, transverse frame members, and stringers, which all share in stress loads and may be readily repaired if damaged. T-37 and T-34 both use semi-monocoque fuselages.

Front 55

Describe full cantilever wing construction.

Back 55

All bracing is internal.

Front 56

• Steady airflow-

Back 56

exists if at every point in the airflow static pressure, density, temperature, and velocity remain constant over time. A particle of air follows the same path as the preceding particle.

Front 57

• Streamline

Back 57

is the path that air particles follow in steady airflow.

Front 58

• Streamtube

Back 58

a collection of streamlines forms a streamtube, which contains a flow just as effectively as a tube with solid walls. A streamtube is a closed system, therefore total mass and total energy must remain constant.

Front 59

Describe the relationship between airflow velocity and cross sectional area within a streamtube using the continuity equation.

Back 59

•Continuity Equation (A1V1 = A2V2)
•If the cross sectional area decreases on one side of the equation, the velocity must increase on the same side so both sides remain equal. Velocity and area in a streamtube are inversely related.

Front 60

Describe the relationship between total pressure, static pressure, and dynamic pressure within a streamtube using Bernoulli’s equation.

Back 60

•Bernoulli’s Equation PT = PS + q
•PT = Total pressure, also called Head Pressure (HT) equals the sum of Static Pressure (PS) + dynamic pressure (q = ½ρV2)
•As with total energy, total pressure also remains constant within a closed system. As area in a streamtube decreases, velocity increases, therefore, “q” must increase(q contains V2). Since q increases, PS must decrease.

Front 61

List the components of the pitot static system.

Back 61

Pitot Tube, Static Pressure Source, and the Black Box

Front 62

State the type of pressure sensed by each component of the pitot static system.

Back 62

•Pitot Tube- collects total pressure (PT)
•Static Pressure Port- collects ambient static pressure (PS)
•Black Box- Takes static pressure and subtracts it from the total pressure with a diaphragm. Through a series of springs and levers, the remaining static pressure, which is equal to dynamic pressure, is displayed on a pressure gauge inside the cockpit…the IAS gauge.
q = PT - PS

Front 63

Define indicated airspeed, calibrated airspeed, equivalent airspeed, true airspeed, and ground speed.
•Indicated Airspeed (IAS)

Back 63

instrument indication for the dynamic pressure the airplane is creating during flight.

Front 64

Define indicated airspeed, calibrated airspeed, equivalent airspeed, true airspeed, and ground speed.
•Calibrated Airspeed (CAS)

Back 64

IAS corrected for instrument error-installation and position error. (Often ignored in calculations)

Front 65

Define indicated airspeed, calibrated airspeed, equivalent airspeed, true airspeed, and ground speed.
•Equivalent Airspeed (EAS)

Back 65

Calibrated Airspeed corrected for Compressibility Error. EAS = TAS at sea level on a standard day that produces the same dynamic pressure as the actual flight condition (often ignored)

Front 66

Define indicated airspeed, calibrated airspeed, equivalent airspeed, true airspeed, and ground speed.
•True Airspeed (TAS)

Back 66

Actual velocity at which an airplane moves through an air mass. It is EAS corrected for Density. TAS is IAS (CAS and EAS are very minor and ignored) corrected for the difference between the local air density (ρ) and the density of the air at sea level on a standard day (ρo)
•TAS will equal IAS only under standard day, sea level conditions.
•Since air density decreases when you increase temperature or altitude, if IAS remains constant while climbing from sea level to some higher altitude, TAS must increase.
TAS = √(ρo/ρ) ∙ IAS

Front 67

Define indicated airspeed, calibrated airspeed, equivalent airspeed, true airspeed, and ground speed.
•Ground Speed (GS)

Back 67

measure of airplanes speed over ground. TAS corrected for wind.
GS = TAS – headwind or GS = TAS + tailwind

Front 68

Mach number (M)

Back 68

ratio of airplane’s true airspeed to the local speed of sound

M = (TAS/LSOS)

Front 69

Critical Mach Number (Mcrit)

Back 69

Supersonic airflow exist somewhere on the airplane, usually the upper surface of wing.

Front 70

Describe the effects of altitude on Mach number and critical Mach number.

Back 70

• An increase in altitude would increase Mach number and Critical Mach number because the local speed of sound would decrease. The speed of sound is temperature dependant and an increase in altitude results in a decrease in temperature which also reduces the speed of sound.

Front 71

Pitch Attitude (θ)

Back 71

angle between an airplane’s longitudinal axis and the horizon

Front 72

Flight Path

Back 72

is the path described by an airplane’s center of gravity as it moves through an air mass.

Front 73

Relative Wind

Back 73

airflow the airplane experiences as it moves through the air. Equal in magnitude and opposite in direction to flight path.

Front 74

Angle of Attack (α)

Back 74

angle between the relative wind and the chordline of an airfoil. Flight path, relative wind, and angle of attack should never be inferred from pitch attitude.

Front 75

Mean Camber Line

Back 75

line drawn halfway between the upper and lower surfaces.

Front 76

Positive Camber

Back 76

if mean camber line is above the chordline

Front 77

Negative Camber

Back 77

if the mean camber line is below the chordline.

Front 78

Symmetric Airfoil

Back 78

If the mean camber line is coincident with the chordline.

Front 79

Aerodynamic Center

Back 79

or quarter chord point, is the point along the chordline where all changes in the aerodynamic force takes place. On subsonic airfoils, the AC is located approximately one quarter (between 23% and 27%) of the length of the chord from the leading edge.

Front 80

Airfoil Thickness

Back 80

height of the airfoil profile. The point of max thickness corresponds to the aerodynamic center.

Front 81

Spanwise Flow

Back 81

airflow that travels along the span of the wing parallel to the leading edge. Does not produce lift.

Front 82

Chordwise Flow

Back 82

air flowing at right angles to the leading edge of an airfoil. It is the only airflow that produces lift.

Front 83

Aerodynamic Force (AF)

Back 83

force that is the result of pressure and friction distribution over an airfoil, and can be resolved into two components, lift and drag.

Front 84

Lift (L)

Back 84

component of the aerodynamic force acting perpendicular to the relative wind.

Front 85

Drag (D)

Back 85

component of the aerodynamic force acting parallel to and in the same direction as the relative wind.

Front 86

Describe the effects on dynamic pressure, static pressure, and the aerodynamic force as air flows around a cambered airfoil and a symmetric airfoil.
•Symmetric Airfoil

Back 86

At zero angle of attack produces identical velocity increases and static pressure decreases on both the upper and lower surfaces. Since there is no pressure differential perpendicular to the relative wind, the airfoil produces zero net lift.

Front 87

Describe the effects on dynamic pressure, static pressure, and the aerodynamic force as air flows around a cambered airfoil and a symmetric airfoil.
•Cambered Airfoil

Back 87

Is able to produce an uneven pressure distribution even at zero AOA. Because of the positive camber, the airflow above the wing will be greater than the velocity below the wing. The static pressure on the upper surface will be less than the static pressure on the lower surface, creating a pressure differential thus creating a lifting force.

Front 88

Describe the effects of changes in angle of attack on the pressure distribution and aerodynamic force of cambered and symmetric airfoils.

Back 88

• Increasing the angle of attack on any airfoil causes the area of the streamtube above the wing to decrease. This produces a greater velocity increase above the wing than below the wing. The greater velocity above the wing will create a pressure differential on a symmetric airfoil and will increase the pressure differential o a cambered airfoil. The greater pressure differential on the airfoil will increase the magnitude of the aerodynamic force.

Front 89

Describe the effects of changes in density, velocity, surface area, camber, and angle of attack on lift.

Back 89

•An increase in density or velocity will produce greater lift.
•An increase in wing surface area produces greater lift.
•Increase Camber will produce greater lift.
•Increase AOA will produce greater lift.

Front 90

List the factors affecting lift that the pilot can directly control.

Back 90

AOA, Velocity, Density, Surface Area, Camber

Front 91

Compare and contrast the coefficients of lift generated by cambered and symmetric airfoils.

Back 91

•Positive Camber
At zero AOA, the positive camber airfoil has a positive CL
•Negative Camber
At zero AOA, the negative camber airfoil has a negative CL
•Symmetric Airfoil
At zero AOA, the symmetric airfoil has a CL = 0

Front 92

Describe the relationships between weight, lift, velocity, and angle of attack in order to maintain straight and level flight, using the lift equation.

Back 92

In order to maintain level flight while increasing angle of attack, velocity must decrease. Otherwise, lift will be greater than weight, and the airplane will climb. Velocity and AOA are inversely related in level flight.

L = qSCL = 1/2ρV2SCL

Front 93

Define boundary layer.

Back 93

that layer of airflow over a surface that demonstrates local airflow retardation due to viscosity. No more than 1mm thick at the leading edge of an airfoil, and grows in thickness as it moves aft over the surface.

Front 94

List and describe the types of boundary layer airflow.

Back 94

•Laminar Flow
o Air molecules move smoothly along in streamlines. Produces very little friction, but is easily separated from the surface.

•Turbulent Flow
o Streamlines break up and the flow is disorganized and irregular. Turbulent layers produce higher friction drag, but adheres to the upper surface of the airfoil, delaying boundary layer separation.

Front 95

State the advantages and disadvantages of each type of boundary layer airflow.

Back 95

•Laminar Flow
oAdvantages- little friction
oDisadvantages- easily separated from the surface

•Turbulent Flow
oAdvantages- adheres to upper surface of airfoil, delaying boundary layer separation.
oDisadvantages- high friction drag

Front 96

State the cause and effect of boundary layer separation.

Back 96

•The adverse pressure gradient impedes the flow of the boundary layer
•If the boundary layer does not have sufficient kinetic energy to overcome the adverse pressure gradient, the lower levels of the boundary layer will stagnate
•The boundary layer will separate from the surface and cause the airfoil to lose the suction pressure that creates lift.

Front 97

Define stall and state the cause of the stall.

Back 97

•Stall
ois a condition of flight where an increase in AOA has resulted in a decrease in CL.

oThe only cause of a stall is excessive AOA beyond CLmax

Front 98

Define and state the importance of CLmax and CLmax AOA.

Back 98

•CLmax
is the peak Coefficient of Lift and any increase in AOA beyond CLmax AOA produces a decrease in CL

•CLmax AOA
is known as stalling AOA or critical AOA and the region beyond CLmax AOA is the stall region. Regardless of the flight conditions or airspeed, the wing will always stall beyond the same AOA.

Front 99

State the procedure for stall recovery.

Back 99

•The only action necessary for stall recovery is to decrease the AOA below CLmax AOA.

Front 100

List common methods of stall warning, and identify those used for the T-34 and T-37.

Back 100

•Common methods of stall warning are: AOA indicators, rudder pedal shakers, stick shakers, horns, buzzers, warning lights, and electronic voices.
•T-34- AOA indicator, AOA indexer and rudder pedal shakers that receive their input from an AOA probe on left wing.
•T-37- Aerodynamic stick shaker.

Front 101

State the stalling AOA of the T-34C

Back 101

•The T-34C AOA indicator is calibrated so that the airplane stalls between 29.0 and 29.5 units AOA regardless of airspeed, nose attitude, weight, or altitude.

Front 102

Define stall speed.

Back 102

is the minimum true airspeed required to maintain level flight at CLmax AOA.

Front 103

State the purpose of high lift devices.

Back 103

•Primary purpose of high lift devices is to reduce takeoff and landing speeds by reducing stall speed.

Front 104

State the effect of boundary layer devices on the coefficient of lift, stalling AOA, and stall speed. (See graph pg 1.4-15)

Back 104

•Coefficient of lift is increased
•Stalling AOA is increased
•Stall Speed is decreased

Front 105

Describe different types of boundary layer control devices.

Back 105

•Fixed Slots
gaps located at the leading edge of a wing that allow air to flow from below the wing to the upper surface.

•Slats
are moveable leading edge sections used to form automatic slots.

Front 106

Describe the operation of boundary layer control devices.

Back 106

•Fixed Slots
High pressure air from the leading edge stagnation point is directed through the slot, which acts as a nozzle converting the static pressure into dynamic pressure. The high kinetic energy air leaving the nozzle increases the energy of the boundary layer and delays separation.

•Slats
when slats are deployed it opens a slot.

Front 107

State the effect of flaps on the coefficient of lift, stalling AOA, and stall speed. (See graph pg 1.4-16)

Back 107

•Coefficient of lift is increased
•Stalling AOA (CLmax AOA) decreases
•Stall speed is decreased

Front 108

Describe different types of flaps.
State the methods used by each type of flap to increase the coefficient of lift.
• Plain Flap

Back 108

o simple hinged portion of the trailing edge that is forced down into the air stream to increase the camber of the airfoil.

Front 109

Describe different types of flaps.
State the methods used by each type of flap to increase the coefficient of lift.
• Split Flap

Back 109

o is a plate deflected from the lower surface of the airfoil. It creates a lot of drag because of the turbulent air between the wing and defected surface.

Front 110

Describe different types of flaps.
State the methods used by each type of flap to increase the coefficient of lift.
• Slotted Flap

Back 110

o similar to the plain flap, but moves away from the wing to open a narrow slot between the flap and wing for boundary layer control.

Front 111

Describe different types of flaps.
State the methods used by each type of flap to increase the coefficient of lift.
• Fowler Flap

Back 111

o used extensively on larger airplanes. When extended, it moves down increasing the camber, and aft causing a significant increase in wing area as well as opening a slot for boundary layer control.

Front 112

Describe different types of flaps.
State the methods used by each type of flap to increase the coefficient of lift.
• Leading Edge Flaps

Back 112

o Devices that change the wing camber at the leading edge of the airfoil. Similar to a trailing edge plain flap.

Front 113

State the stall pattern exhibited by rectangular, elliptical, moderate taper, high taper, and swept wing platforms.

Back 113

• Rectangular (λ = 1.0)
o lift distribution is due to low lift coefficients at the tip and high lift coefficients at the root. Since the area of the highest lift coefficient will stall first, the rectangular wing has a strong root stall tendency. Provides adequate stall warning and aileron effectiveness.

Front 114

State the stall pattern exhibited by rectangular, elliptical, moderate taper, high taper, and swept wing platforms.

Back 114

• Elliptical Wing
o Has even distribution of lift from the root to the tip and produces minimum induced drag. All sections stall at the same angle of attack. Little advanced warning and aileron effectiveness may be lost near stall.

Front 115

State the stall pattern exhibited by rectangular, elliptical, moderate taper, high taper, and swept wing platforms.

Back 115

• Moderate Taper (λ = 0.5)
o have a lift distribution and stall pattern that is similar to the elliptical wing.

Front 116

State the stall pattern exhibited by rectangular, elliptical, moderate taper, high taper, and swept wing platforms.

Back 116

• High Taper (λ = 0.25)
o Desirable form the standpoint of structural weight, stiffness, and wingtip vortices. Tapered wings produce most of the lift toward the tip, and have a strong tip stall tendency.

Front 117

State the stall pattern exhibited by rectangular, elliptical, moderate taper, high taper, and swept wing platforms.

Back 117

• Swept Wing
o Used on high speed aircraft because they reduce drag and allow the airplane to fly at higher Mach numbers. Have similar lift distribution to a tapered wing, stall easily and have a strong tip stall tendency. When wingtip stalls, it rapidly progresses over the remainder of the wing.

Front 118

State the advantages and disadvantages of tapering the wings of the T-34 and T-37.

Back 118

• Advantages
o The T-37 and T-34 use tapered wings because they reduce weight, improve stiffness, and reduce wingtip vortices.

• Disadvantages
o Even stall progression of tapered wings is undesirable because the ailerons are located near the tip. As stall progresses, the pilot will lose lateral control.

Front 119

State the purpose of wing tailoring.

Back 119

• Purpose of wing tailoring is to create a root to tip stall progression and give the pilot some stall warning while ensuring that the ailerons remain effective up to a complete stall.

Front 120

Describe different methods of wing tailoring.
• Geometric Twist

Back 120

• Geometric Twist
o Is a decrease in angle of incidence from wing root to wing tip. The root section is mounted at some angle of attack to the longitudinal axis and the leading edge of the remainder of wing is gradually twisted downward. This results in a decreased angle of attack at the wingtip due to its lower angle of incidence. The root stalls first because of its higher AOA.

Front 121

Describe different methods of wing tailoring.
• Aerodynamic Twist

Back 121

• Aerodynamic Twist
o Is a decrease in camber from wing root to wingtip. This causes a gradual change in cross section shape from positive camber at the wing root to a symmetric shape at the wingtip. Since positive camber airfoils stall at lower angles of attack, the wing root stalls before the wingtip.

Front 122

State the types of wing tailoring used on the T-34.

Back 122

oT-34 wing is geometrically twisted 3.1°
oT-34 wings are aerodynamically twisted to create a reduced camber at the tip.

Front 123

State the types of wing tailoring used on the T-37.

Back 123

•T-37
oWing is geometrically twisted 2.5°
oWings are aerodynamically twisted to create a reduced camber at the tip.

Front 124

• Drag

Back 124

Is the component of the aerodynamic force that is parallel to the relative wind and acts in the same direction.

D = 1/2ρV2SCD

Front 125

• Total Drag

Back 125

DT = DP + Di

Front 126

• Parasite Drag (DP)

Back 126

All drag that is not associated with the production of lift.

Front 127

• Induced Drag (Di)

Back 127

Is that portion of total drag associated with the production of lift

Front 128

List the three major types of parasite drag.

Back 128

Form Drag, Friction Drag, and Interference Drag

Front 129

State the cause of each major type of parasite drag.

Back 129

•Form Drag
oAlso known as pressure or profile drag, is caused by the airflow separation from a surface and the wake that is created by that separation.
•Friction Drag
oDue to viscosity, a retarding force called friction drag is created in the boundary layer.
•Interference Drag
oGenerated by mixing of streamlines between one or more components

Front 130

State the aircraft design feature that reduce each major type of parasite drag.

Back 130

•To reduce form drag, the fuselage, bombs, and other surfaces exposed to the airstream are streamlined.
•Friction Drag can be reduced by smoothing the exposed surfaces of the airplane through painting, cleaning, waxing, or polishing.
•Interference Drag can be minimized by proper fairing and filleting, which allows streamlines to meet gradually rather than abruptly.

Front 131

Describe the effects in changes in density, velocity, and equivalent parasite area (f) on parasite drag, using the parasite drag equation.

Back 131

DP = 1/2ρV2f = qf
•Parasite Drag varies directly with velocity squared. If you double you speed, you will create four times a much parasite drag.
•An increase in altitude will decrease density.
•Equivalent parasite area is a mathematically computed value equal to the area of a flat plate perpendicular to the relative wind that would produce the same amount of drag as form drag, friction drag and interference drag combined. It is not cross sectional area of the airplane.

Front 132

Describe the effects of upwash and downwash on the lift generated by an infinite wing.

Back 132

For an infinite wing, the upwash exactly balances the downwash resulting in no net change in lift. Upwash and downwash exist any time an airfoil produces lift.

Front 133

Describe the effects of upwash and downwash on the lift generated by a finite wing.

Back 133

• The wind flows around the wingtips, combines with the chordwise flow that has already produced lift and adds to the downwash.
• Downwash approximately doubles by this process due to the spanwise airflow moving around the formation of wingtip vortices.

Front 134

State the cause on induced drag.

Back 134

•Caused by parallel component of lift and acts in the same direction as drag and tends to retard the forward motion of the airplane.
•Induced drag varies inversely with velocity and directly with angle of attack

Front 135

State the aircraft design features that reduce induced drag.

Back 135

•Install devices that impede spanwise airflow going around wingtips: winglets, wingtip tanks, and missile rails.

Front 136

Describe the effects of changes in lift, weight, density, and velocity on induced drag, using the induced drag equation.

Back 136

•Increase in weight will increase induced drag.
•Induced drag is reduced by increasing density (ρ), velocity (V), or wingspan (b).
•In level flight where lift is constant, induced drag varies inversely with velocity, and directly with angle of attack.

Front 137

Describe the effects of changes in velocity on total drag. (See pg 1.5-8)

Back 137

•An increase in velocity will increase parasite drag and decrease induced drag.
•A decrease in velocity will decrease parasite drag and will increase induced drag.

Front 138

Define and state the purpose of the lift to drag ratio.

Back 138

•Lift to Drag ratio
oDetermines efficiency of an airfoil.
oHigh lift to drag ratio indicates a more efficient airfoil.

Front 139

State the importance of L/DMAX

Back 139

•Produces the minimum total drag.
•Parasite drag and induced drag are equal.
•Produces the greatest lift to drag ratio.
•Most efficient AOA.

Front 140

Describe the relationship between thrust and power.

Back 140

PR = (TR∙V)/325

• Power required is Thrust required times velocity divided by 325.

• Thrust horsepower only depends on thrust and velocity. The term power (P) is used rather than thrust horsepower (THP) or shaft horsepower (SHP).

Front 141

Define thrust required and power required.

Back 141

• Thrust Required (TR)
o Amount of thrust required to overcome drag and is expressed in pounds.

• Power Required (PR)
o Amount of power that is required to produce thrust required

Front 142

Describe how thrust required and power required varies with velocity.

Back 142

• Power required is dependant on Thrust required and Velocity.

Front 143

State the location of L/DMAX on the thrust required and power required curves. (pg 1.6-4)

Back 143

• Thrust Required Curve, L/DMAX is at bottom of curve.

• Power Required Curve, L/DMAX is to the right of the bottom of the curve.

Front 144

Define thrust available and power available.

Back 144

• Thrust Available (TA)
o Amount of thrust that the airplane’s engines are actually producing at a given throttle setting, velocity, and density.

• Power Available (PA)
o Amount of power that the airplane’s engine is actually producing at a given throttle setting, velocity, and density.

Front 145

Describe the effects of throttle setting , velocity, and density on thrust available and power available for a turbojet engine.

Back 145

•Thrust Available
-Max engine output occurs at full throttle
-Turbojets do not suffer a decrease in thrust available with velocity because ram effect overcomes the decreased acceleration.
-As density decreases, thrust available also decreases.
•Power Available
-Max power available occurs at full throttle
-As velocity increases, power available will increase linearly
-Power available decreases with a decrease in density.

Front 146

Describe the effects of PCL setting, velocity, and density on thrust available and power available for a turboprop engine.

Back 146

• Thrust Available
-Max engine output occurs at full throttle
-Since propeller can only accelerate the air to a max velocity, as the velocity of the incoming air increases, the air is accelerated less through the propeller, and thrust available decreases
-As density decreases, thrust available also decreases

•Power Available
-Max power available occurs at full throttle
-Will initially increases, but will then decrease due to a decrease in thrust available.
-Power available decreases with a decrease in density.

Front 147

Define thrust horsepower, shaft horsepower, and propeller efficiency.

Back 147

•Thrust Horsepower (THP)
Is propeller output

•Shaft Horsepower (SHP)
Engine output

•Propeller Efficiency (p.e.)
Ability of the propeller to turn engine output into thrust.

Front 148

State the relationship between thrust horsepower, shaft horsepower, and propeller efficiency.

Back 148

•Under ideal conditions, SHP would equal THP, but due to friction in the gearbox and propeller drag, THP is always less than SHP. Propeller efficiency is always less than 100%.

THP = SHP ∙ p.e.

Front 149

State the flat rated shaft horsepower and the Navy limited shaft horsepower of the T-34C PT6A-25 engine.

Back 149

•Flat rated horsepower of T-34C
550 SHP (1315 ft-lbs of torque)

•Navy limit
425 SHP (1015 ft-lbs of torque) to extend service life of engine.

Front 150

State the instrument indications for the flat rated shaft horsepower and the Navy limited shaft horsepower of the T-34C PT6A-25 engine.

Back 150

• Flat rated horsepower of T-34C
o 550 SHP (1315 ft-lbs of torque)

• Navy limit
o 425 SHP (1015 ft-lbs of torque) to extend service life of engine.

Front 151

State the sea level rated thrust of each T-37B J69-T-25A engine.

Back 151

•Flat rated at 1025 pounds of thrust at 100% RPM, but is limited to 95% RPM for continuous operation.

Front 152

State the instrument indications for the sea level rated thrust of the T-37B J69-T-25A

Back 152

•Flat rated at 1025 pounds of thrust at 100% RPM, but is limited to 95% RPM for continuous operation.

Front 153

Define thrust excess (TE) and power excess (PE).

Back 153

•TE occurs if thrust available is greater than thrust required at a particular velocity.
TE = TA - TR

•PE is calculated in a similar manner as TE and will also produce an acceleration, a climb, or both.
PE = PA -PR

Front 154

State the effects of a thrust excess or a power excess.

Back 154

•Thrust Excess
-Positive TE causes an acceleration, a climb, or both depending on AOA
-Negative TE is called thrust deficit and has the opposite effect.

•Power Excess
-Will cause an acceleration, climb, or both
-Power deficit will cause a descent, a deceleration, or both

Front 155

State the conditions necessary to achieve the maximum thrust excess and maximum power excess for a turbojet and a turboprop airplane.

Back 155

•Max Thrust Excess
-Max TE occurs at full throttle setting.
-For a turbojet, max thrust excess occurs at L/DMAX.
-For a turboprop, max thrust excess occurs at a velocity less than L/DMAX.

•Max Power Excess
-Turbojet- max power excess occurs at a velocity greater than L/DMAX.
-Turboprop- max power excess occurs at L/DMAX.

Front 156

Describe the effects of changes in weight on thrust required, power required, thrust available, and power available. (See pg 1.6-8)

Back 156

An increase in weight will shift the TR and TA curve UP and RIGHT.

Front 157

Describe the effects of changes in weight on maximum thrust excess and maximum power excess, and on the airspeeds necessary to achieve max thrust excess and max power excess.

Back 157

• Thrust excess and power excess decrease at every AOA and velocity.

Front 158

Describe the effects of changes in altitude on thrust required, power required, thrust available, and power available.

Back 158

•Thrust Required
Increase in altitude, the thrust required curve shifts to the RIGHT, NOT UP.
•Power Required
Increase in altitude, the power required curve shifts UP AND TO THE RIGHT.
•Thrust Available
Decreases at higher altitudes due to reduction in air density.
•Power Available
Decreases at higher altitudes due to reduction in air density.

Front 159

Describe the effect of changes in altitude on max thrust excess and max power excess and on the airspeeds necessary to achieve max thrust and max power excess.

Back 159

•Max Thrust Excess
TE will decrease with an increase in altitude due to the decrease in thrust available.
•Max Power Excess
PE will decrease as altitude increases because power available decreases and power required increases.
•The airspeed necessary to achieve max thrust and max power excess will INCREASE.

Front 160

Describe the effects of changes in configuration on thrust required, power required, thrust available, and power available.

Back 160

•Lowering Landing Gear
-TR and PR increase. Curve moves UP
-TA and PA are not affected by the landing gear.

•Lowering Flaps
-TR and PR increase. Curve moves UP AND LEFT.
-TA and PA are not affected by the flaps.

Front 161

Describe the effects of changes in configuration on maximum thrust excess and max power excess, and on the airspeeds necessary to achieve max thrust and max power excess.

Back 161

•Lowering Landing Gear
-Thrust and power excess will decrease with deployment of landing gear because thrust and power required increase.

•Lowering Flaps
-Thrust ad power excess will decrease with deployment of the flaps because thrust and power required increase.
•The airspeed necessary to achieve max thrust and max power excess will DECREASE.