FM 3-04.203 Fundamentals of Flight (under construction, not ready for use)

Question 1

Newton’s three laws of motion are:

Answer 1

• inertia
• acceleration
• action/reaction.

Question 2

Define 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

Define 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

Define Action/Reaction

Answer 4

For every action, there is an equal and opposite reaction.

Question 5

Bernoulli’s Principle

Answer 5

*****

Question 6

Venturi Effect

Answer 6

*****

Question 7

Airflow and the Airfoil: As velocity of the airflow increases, static pressure decreases _________________________.

Answer 7

above and below the airfoil.

Question 8

Airflow and the Airfoil: The air usually has to travel a __________ distance over the upper surface; thus, there is a ________________ and _________________ over the upper surface than the lower surface.

Answer 8

greater distance greater velocity increase static pressure decrease

Question 9

The static pressure differential on the upper and lower surfaces produces about ______________ of the aerodynamic force, called lift.

Answer 9

75 percent

Question 10

The remaining 25 percent of the force is produced as a result of __________________________________ and ______________________________________.

Answer 10

action/reaction from the downward deflection of air as it leaves the trailing edge of the airfoil and by the downward deflection of air impacting the exposed lower surface of the airfoil.

Question 11

Define Vectors

Answer 11

Vectors are quantities with a magnitude and direction.

Question 12

The remaining 25 percent of the force is produced as a result of __________________________________ and ______________________________________.

Answer 12

action/reaction from the downward deflection of air as it leaves the trailing edge of the airfoil and by the downward deflection of air impacting the exposed lower surface of the airfoil.

Question 13

Define scalars

Answer 13

Scalars are quantities described by size alone such as area, volume, time, and mass.

Question 14

Examples of vector quantities are:

Answer 14

Velocity, acceleration, weight, lift, and drag

Question 15

The two basic types of airfoils are

Answer 15

symmetrical and nonsymmetrical.

Question 16

Define Blade Span

Answer 16

The length of the rotor blade from point of rotation to tip of the blade.

Question 17

Define Wing Span

Answer 17

The length of the wing from tip to tip.

Question 18

Define Chord Line

Answer 18

A straight line intersecting leading and trailing edges of the airfoil.

Question 19

Define Chord

Answer 19

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

Question 20

Define Mean Camber Line

Answer 20

A line drawn halfway between the upper and lower surfaces. The chord line connects the ends of the mean camber line. Camber refers to curvature of the airfoil and may be considered curvature of the mean camber line. The shape of the mean camber is important for determining aerodynamic characteristics of an airfoil section. Maximum camber (displacement of the mean camber line from the chord line) and its location help to define the shape of the mean camber line. The location of maximum camber and its displacement from the chord line are expressed as fractions or percentages of the basic chord length. By varying the point of maximum camber, the manufacturer can tailor an airfoil for a specific purpose. The profile thickness and thickness distribution are important properties of an airfoil section.

Question 21

Define Leading-Edge Radius

Answer 21

The radius of curvature given the leading edge shape.

Question 22

Define Flight-Path Velocity

Answer 22

The speed and direction of the airfoil passing through the air. For FW airfoils, flight-path velocity is equal to true airspeed (TAS). For helicopter rotor blades, flight-path velocity is equal to rotational velocity, plus or minus a component of directional airspeed.

Question 23

Define Relative Wind

Answer 23

Air in motion equal to and opposite the flight-path velocity of the airfoil. This is rotational relative wind for rotary-wing aircraft and will be covered in detail later. 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 24

Define Induced Flow

Answer 24

The downward flow of air (more distinct in rotary-wing).

Question 25

Define Resultant Relative Wind

Answer 25

Relative wind modified by induced flow.

Question 26

Define Angle of Attack (AOA)

Answer 26

The angle measured between the resultant relative wind and chord line.

Question 27

Define Angle of Incidence (FW Aircraft)

Answer 27

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

Question 28

Define Angle of Incidence (Rotary-Wing Aircraft)

Answer 28

The angle between the chord line of a main or tail-rotor blade and rotational relative wind (tip-path plane). It is usually referred to as blade pitch angle. For fixed airfoils, such as vertical fins or elevators, angle of incidence is the angle between the chord line of the airfoil and a selected reference plane of the helicopter.

Question 29

Center of Pressure

Answer 29

The point along the chord line of an airfoil through which all aerodynamic forces are considered to act. Since pressures vary on the surface of an airfoil, an average location of pressure variation is needed. As the AOA changes, these pressures change and center of pressure moves along the chord line.

Question 30

Aerodynamic Center

Answer 30

The point along the chord line where all changes to lift effectively take place. If the center of pressure is located behind the aerodynamic center, the airfoil experiences a nose-down pitching moment. Use of this point by engineers eliminates the problem of center of pressure movement during AOA aerodynamic analysis.

Question 31

The symmetrical airfoil (figure 1-9) is distinguished by having identical upper and lower surface designs, ___________________________.

Answer 31

the mean camber line and chord line being coincident and producing zero lift at zero AOA.

Question 32

Symmetrical airfoil: One advantage is the center-of-pressure _____________________ .

Answer 32

remains relatively constant under varying angles of attack (reducing the twisting force exerted on the airfoil).

Question 33

Symmetrical: advantages. Construction and cost?

Answer 33

Another advantage is it affords ease of construction and reduced cost.

Question 34

The nonsymmetrical airfoil (figure 1-10) has different upper and lower surface designs, ____________________________ .

Answer 34

with a greater curvature of the airfoil above the chord line than below. The mean camber line and chord line are not coincident.

Question 35

Does the non symmetrical airfoil produce lift at 0 degrees AOA?

Answer 35

The nonsymmetrical airfoil design produces useful lift even at negative angles of attack.

Question 36

1-19

Answer 36

continue