Presentation 6: Fundamentals of Aircraft Aerodynamics

Question 1

Perfect Gas Law

Answer 1

p = [rho] R T

R = 1716 ft*lb/slugs*R

R = 287.05 N*m/kg*K

Question 2

Assumptions of the Standard Atmosphere

Answer 2

That the atmosphere is a homogeneous gas of uniform composition that satisfies the perfect gas law.

Question 3

Effects of Water Vapor

Answer 3

Affects engine performance and supersonic aerodynamics

Question 4

Standard Sea-Level Properties

Answer 4

g = 32.17 ft/s^2 = 9.806 m/s^2

p = 2116.2 lb/ft^2 = 1.013 x 10^5 N/m^2

T = 59 deg F = 518.7 deg R = 15 deg C = 288.2 K

rho = 0.002377 slug/ft^3 = 1.225 kg/m^3

Question 5

Tropopause

Answer 5

Transition between the troposphere (negative temperature gradient) and the stratosphere (isotherm).

At 36,089 ft

Temperature is -69.7 deg F

Question 6

Temperature Variation w/ Altitude

Answer 6

T = T₁ + a(h-h₁)

a = -0.00356616 deg F/ft

a is the “temperature lapse rate”

Question 7

Temperature Ratio to S.L. Temp

(Theta)

Answer 7

Theta = 1-6.875 x 10^-6 (h)

Question 8

Pressure Ratio to S.L. Pressure

(Delta)

Answer 8

Delta = [Theta]^5.2561

Question 9

Density Ratio to S.L. Density

(Sigma)

Answer 9

Sigma = [Theta]^4.2561

Question 10

Kinematic Viscosity

Answer 10

[nu] = [mu] / [rho]

Question 11

Reynolds Number

Answer 11

Re = V*l / [nu]

Re = [rho]*V*L / [mu]

Question 12

Indicated Airspeed (IAS)

Answer 12

The direct reading from the airspeed indicator. This represents the airplane’s speed through the air, not necessarily its speed across the ground.

Question 13

Cailbrated Airspeed (CAS)

Answer 13

The indicated airspeed corrected for instrument position and instrument error.

Different for each uniqure aircraft and its position of the pitot tube.

No direct reading of CAS in the cockpit, pilot must refer to handbook for particular aircraft.

Question 14

True Airspeed (TAS)

Answer 14

Corrects for the effect of change in altitude on airspeed.

The airspeed indicator is calibrated for sea-level, not altitude.

TAS can be approximated by increasing the IAS by 2% per thousand feet of altitude.

Question 15

The Anatomy of an Airplane

Question 16

Flight Mechanics

Answer 16

The study of the motions of bodies (aircraft and rockets) through a fluid.

Question 17

Four Forces of Flight

Answer 17

Lift, Drag, Weight, Thrust

Lift is always perpendicular to the relative wind

Drag is always parallel to the relative wind

Weight is always towards the center of the Earth

Question 18

Four Forces in Climbing Flight

Question 19

Turning, Banking the Aircraft

Answer 19

[phi] = bank (roll) angle

Question 20

Three Equations of Motion

Question 21

Assumptions of the Three Equations of Motion

Answer 21

Flat Earth

No yaw component

Free stream velocity is always parallel to the symmetry plane of the aircraft.

Question 22

Sources of Aerodynamic Force

Answer 22

Pressure: acts perpendicular to the surface

Shear stress: acts parallel to the surface

Question 23

Derivation of Bernoulli’s Equation

Question 24

Euler’s Equation

Answer 24

dp = -[rho] V dV

Question 25

Moment

Answer 25

Rotates a body

An increase in angle of attack is a positive moment, by convention

Question 26

Parameters of the Aerodynamic Force

Answer 26

density, free-stream velocity, surface area, angle of attack, viscosity, compressibility

Question 27

Buckingham Pi Theorem

Answer 27

A function with “n” varialbes can be described with “n-k” non-dimensional variables

p = n - k

where:

p = number of dimension-less variables needed

n = number of physical variables in physical relation

k = nubmer of fundamental dimensions required to describe the physical variables

Question 28

Lift Coefficient

Answer 28

CL = L / qS

where q is the dynamic pressure

Question 29

Mach Number

Answer 29

M = V / a

where a is the speed of sound

Question 30

Drag Coefficient

Answer 30

CD = D / qS

where q is the dynamic pressure

Question 31

Moment Coefficient

Answer 31

CM = M / qS

where q is the dymanic pressure

Question 32

Dynamic Pressure

Answer 32

q = 1/2 [rho] V^2

Question 33

Wetted Area

Answer 33

Surfae upon which the pressure and shear distributions act

Meaningful geometric quantity when discussing aerodynamic force

Not common

Question 34

Planform Area

Answer 34

The projected area we can see when looking down at the wing or aircraft (shadow)

Most common definition of S

Question 35

Base Area

Answer 35

Most common when analyzing slender bodies (like missiles)

Question 36

Center of Pressure

Answer 36

The centroid of the distributed load

Question 37

Aerodynamic Center

Answer 37

The point about which moments are independent of angle of attack

Fixed point on an airfoil

xa.c. / c = -m / a

Question 38

Anatomy of an Airfoil

Question 39

NACA Four Digit Airfoils