Aviation Aerodynamics for Helicopters (Rotary Wing Aircraft)

Question 1

Lift

Answer 1

Opposes the downward force of weight, is produced by the dynamic effect of the air acting on the airfoil and acts perpendicular to the flightpath through the center of lift

Question 2

Weight

Answer 2

The combined load of the aircraft itself, the crew, the fuel, and the cargo or baggage. Weight pulls the aircraft downward because of the force of gravity. It opposes lift and acts vertically downward through the aircraft’s center of gravity

Question 3

Thrust

Answer 3

The force produced by the power plant/propeller or rotor. It opposes or overcomes the force of drag. As a general rule, it acts parallel to the longitudinal axis.

Question 4

Drag

Answer 4

A rearward, retarding force caused by disruption of airflow by the wing, rotor, fuselage, and other protruding objects. Drag opposes thrust and acts rearward parallel to the relative wind.

Question 5

Angle of attack (AOA)

Answer 5

Angle at which the airfoil meets the oncoming airflow (or vice versa)

Question 6

Blade span

Answer 6

The length of the rotor blade from center of rotation to tip of the blade

Question 7

Chord line

Answer 7

A straight line intersecting leading and trailing edges of the airfoil

Question 8

Chord

Answer 8

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

Question 9

Mean camber line

Answer 9

A line drawn halfway between the upper and lower surfaces of the airfoil

Question 10

Camber

Answer 10

curvature of the airfoil

Question 11

Leading edge

Answer 11

The front edge of an airfoil

Question 12

Flightpath velocity

Answer 12

The speed and direction of the airfoil passing through the air. For airfoils on an airplane, the flightpath velocity is equal to true airspeed (TAS).

Question 13

Relative wind

Answer 13

Defined as the airflow relative to an airfoil and is created by movement of an airfoil through the air.

Question 14

Trailing edge

Answer 14

The rearmost edge of an airfoil

Question 15

Induced flow

Answer 15

The downward flow of air through the rotor disk

Question 16

Resultant relative wind

Answer 16

Relative wind modified by induced flow

Question 17

AOA

Answer 17

The angle measured between the resultant wind and chord line

Question 18

Angle of incidence (AOI)

Answer 18

The angle between the chord line of a blade and rotor hub. It is usually referred to as blade pitch angle

Question 19

Center of pressure

Answer 19

The point along the chord line of an airfoil through which all aerodynamic forces are considered to act.

Question 20

Hub

Answer 20

On the mast, the attaching point for the root of the blade, and the axis about which blades rotate

Question 21

Tip

Answer 21

The farthest outboard section of the rotor blade

Question 22

Root

Answer 22

The inner end of the blade and is the point that attaches to the hub

Question 23

Twist

Answer 23

The change in blade incidence from the root to the outer blade