Theory Of Rotary Wing Flight

Question 1

Define center of pressure.

Answer 1

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

Question 2

Define airfoil.

Answer 2

Any surface designed to produce lift when air passes over it.

Question 3

List two basic types of airfoils.

Answer 3

Symmetrical

Non-symmetrical

Question 4

Define rotational relative wind as applied to an airfoil.

Answer 4

The flow of wind parallel and opposite to the flight path of an airfoil.

Question 5

Define induced flow.

Answer 5

Downward flow of air through the rotor blades.

Question 6

Define resultant relative wind

Answer 6

Rotational relative wind modified by induced flow.

Question 7

How is angle of incident measured.

Answer 7

The angle between the chord line of an airfoil and the plane of rotation.

Question 8

Define angle of attack

Answer 8

The angle between the chord line of an airfoil and the resultant relative wind.

Question 9

Centrifugal force…

Answer 9

The outward force produced whenever a body moves in a curved path

Provides rigidity to the rotor blades

Question 10

Three adverse effects of coning

Answer 10

Loss of disk area

Loss of total lift

Stress on blades

Question 11

Why is blade twisting necessary?

Answer 11

To distribute the lifting forces more evenly along the blade

Question 12

How is the rotor blade twisted?

Answer 12

Higher AOI at the base and decreases towards the end

Question 13

List the two components of total aerodynamic force.

Answer 13

Lift and drag

Question 14

Describe the relationship of lift to the resultant relative wind.

Answer 14

Perpendicular

Question 15

Describe the relationship between drag and resultant relative wind.

Answer 15

Parallel and in the same direction

Question 16

Which type of drag decreases with an increase of airspeed?

Answer 16

Induced Drag

Question 17

Which type of drag increases with an increase in airspeed.

Answer 17

Parasite drag

Question 18

Define dissymmetry of lift

Answer 18

Dissymmetry of lift is the differential lift between advancing and retreating halves of the rotor disk caused by the different wind flow velocity across each half

Question 19

What causes the advancing blade to flap up

Answer 19

An increase in lift.

Question 20

Define blowback

Answer 20

Change in the attitude of the rotor system

Question 21

Which forces in the lift equation can the pilot control

Answer 21

Coefficient of lift

Airspeed

Question 22

Define centrifugal force

Answer 22

Outward force produced whenever a body moves in a curved path

Question 23

Define rotor blade coning

Answer 23

Upward flexing of the rotor blades

Question 24

Rotor blade coning is a compromised between which two forces

Answer 24

Lift

Centrifugal force

Question 25

Define gyroscopic precession

Answer 25

When a force is applied to a rotating body it will manifest 90 degrees after the application in the direction of rotation

Question 26

Why is blade twisting necessary

Answer 26

To distribute the lifting forces more evenly along the blade

Question 27

Define translating tendency

Answer 27

Tendency of a single rotor helicopter to drift to the right

Question 28

List 4 methods used to overcome translating tendency in single rotor helicopters.

Answer 28

Rigging the cyclic Tilting the mast Left cyclic Automatic flight controls and SAS

Question 29

Describe the relationship of total force to the tip path plane

Answer 29

Perpendicular

Question 30

And the rotor disc is tilted what are the two components of total force

Answer 30

Lift Thrust

Question 31

What are the two flight conditions

Answer 31

Balanced Unbalanced

Question 32

List the 4 rotor blade actions

Answer 32

Rotation Flapping Feathering Hunting

Question 33

Define effective translational lift

Answer 33

When the rotor completely outruns the recirculation of old vortices and begins to work in relatively undisturbed air

Question 34

ETL occurs at what speed

Answer 34

16-24

Question 35

Transverse flow effect occurs at what speed

Answer 35

10-20

Question 36

Define settling with power

Answer 36

When I helicopter settles into its own downwash

Question 37

Where is the three simultaneous conditions required for settling with power

Answer 37

Vertical decent speed of at least 300 fpm 20% to 100% of engine power Slow airspeed less than ETL

Question 38

What is the required recovery procedures for settling with power

Answer 38

Increase airspeed with cyclic Reduce collective (altitude permitting) Adjust RPM to normal range

Question 39

Define autorotation

Answer 39

No engine power is given and main rotor is driven only by the relative wind

Question 40

Describe how to prevent a rotor RPM over speed during auto rotation with turns

Answer 40

Collective control

Question 41

Describe the symptoms of her treating blade stall

Answer 41

Abnormal vibrations Pitch up attitude Left roll

Question 42

Describe the recovery procedure from retreating blade stall

Answer 42

``` Reduce collective pitch Regain control Reduce airspeed Increase rotor rpm to normal operating range Minimize maneuvering Descend to a lower altitude ```