Fixed-Wing Aerodynamics

Question 1

Newton’s three laws of motion are?

Answer 1

Inertia, Acceleration, and Action/reaction.

These laws apply to flight
of any aircraft. A working knowledge of the laws and their applications will assist in understanding aerodynamic principles discussed in this chapter. Interaction between the laws of motion and aircraft mechanical actions causes the aircraft to fly and allows aviators to control such flight.

Question 2

Describe Newton’s First Law: INERTIA

Answer 2

A body at rest will remain at rest, and a body in motion will remain in motion at the same speed and in the same direction unless acted upon by an external force.

Question 3

Describe Newton’s Second Law: ACCELERATION

Answer 3

The force required to produce a change in motion of a body is directly proportional to its mass and rate of change in its velocity.

Question 4

Describe Newton’s Third Law: ACTION/REACTION

Answer 4

For every action, there is an equal and opposite reaction. When an interaction occurs between two bodies, equal forces in opposite directions are imparted to each body.

Question 5

What does Aerodynamic lift look like when comparing it to Newton’s Law of Motion?

Answer 5

Question 6

What are the four force vectors acting on an aircraft?

Answer 6

Lift, Weight, Drag, Thrust

Question 7

What is the, “Chord” of an aircraft?

Answer 7

The length of the chord line from leading edge to trailing edge; it is the characteristic longitudinal dimension of the airfoil section.

Question 8

Define “Relative Wind”.

Answer 8

Air in motion equal to and opposite the flight-path velocity of the airfoil. As an induced airflow may modify flight-path velocity, relative wind experienced by the airfoil may not be exactly opposite its direction of travel.

Question 9

Define “Angle of Incidence”.

Answer 9

The angle between the airfoil chord line and longitudinal axis or other selected reference plane of the airplane.

Question 10

What are the two basic types of airfoils?

Answer 10

The two basic types of airfoils are symmetrical and nonsymmetrical.

Question 11

What type of airfoil does the RC-12X have on it?

Answer 11

Both Symmetrical and nonsymmetrical.

If you look closely on both the inboard of the nacelle and outboard of the nacelle, you can see it.

Question 12

As air flows around an airfoil, a pressure differential develops between the upper and lower surfaces. The differential, combined with air resistance to passage of the airfoil, creates a force on the airfoil. What is this force known as?

Answer 12

TOTAL AERODYNAMIC FORCE (TAF)

Question 13

Define the lift equation.

Answer 13

L = CL x ρ /2 x S x V2

L = lift force

CL = coefficient of lift

ρ /2 = .5 x ρ (rho) = density of the air (in slugs per cubic foot)

S = surface area (in square feet)

V2 = airspeed (in feet per second)

Question 14

Which portions of the Lift Equation can pilots control?

Answer 14

Angle of attack and Airspeed

Question 15

What are the three types of drag?

Answer 15

Parasite

Profile

Induced

Question 16

Which type of drag is created by all of the antennas on the RC12?

Answer 16

Parasite Drag

Question 17

What is the “Basic Weight” of an aircraft?

Answer 17

Basic weight of an aircraft is weight including all hydraulic and oil systems full, trapped and unusable fuel, and all fixed equipment. From basic weight total, it is only necessary to add crew, fuel, cargo, and ammunition (if carried) when determining the aircraft’s gross weight. Basic weight varies with structural modifications and changes of fixed aircraft equipment.

Question 18

Define “Center of Gravity”.

Answer 18

The CG is defined as the theoretical point where all the aircraft’s weight is considered to be concentrated. If an aircraft is suspended by a cable attached to the CG point, it balances like a teeter-totter.

Question 19

Which control in the aircraft would allow you to alter the lateral axis of the aircraft?

Answer 19

The Yoke.

Question 20

What is static stability?

Answer 20

Static stability is the tendency an object possesses after it has been displaced from its equilibrium (figure 7-2, page 7-2). Newton’s first law of motion implies if the sum of the forces and moments about the CG of an object are equal to zero, then no acceleration will take place. This state is called equilibrium.

Question 21

What is the purpose of a dihedral bilt into an airplanes wing?

Answer 21

Dihedral of the wing is the angle between the wing and a plane parallel to the lateral axis, creating a stabilizing moment.