***Rotary Wing Aerodynamics***

Question 1

What allows Tail Rotor Blades to flap?

Answer 1

Tail rotor hinges

Question 2

What is the function of the cyclic stick?

Answer 2

Change aircraft direction/speed

Question 3

What is a function of the collective Pitch Lever?

Answer 3

Allows aircraft to climb or descend

Question 4

What allows the main rotor blades on a fully articulated rotor system to lead and lag?

Answer 4

Drag hinge

Question 5

What is an example of a vector?

Answer 5

Velocity and direction

Question 6

What describes the point at which two or more vectors meet on an airfoil to form a resultant vector?

Answer 6

Center of Pressure

Question 7

What determines whether an airfoil is symmetrical or nonsymmetrical?

Answer 7

Shape

Question 8

What direction does relative wind travel in relation to the movement of an airfoil?

Answer 8

Parallel

Question 9

What is equal to weight on rotary-wing aircraft during straight and level flight?

Answer 9

Lift

Question 10

What is lift equal to weight and thrust and drag equal to zero?

Answer 10

Hover

Question 11

What is the most important factor that affects lift?

Answer 11

Velocity

Question 12

What defines/describes parasite drag?

Answer 12

Increases as airspeed increases

Question 13

What causes dissymmetry of lift?

Answer 13

Differential lift – advancing blade generates more lift that the retreating blade

Question 14

What is most noticeable when entering translational lift?

Answer 14

Transverse flow effect

e. g. - in forward flight, air passing through the rear portion of the rotor disk has a greater downwash angle than air passing through the forward portion. The downward flow at the rear of the rotor disk casues a reduced angle of attack, resulting in less lift. Increased AOA and more lift is produced at the front of the disk.
- Noticeable between 10 - 20 knots
- Result in right roling motion

Question 15

What autorotation phase decreases aircraft airspeed and increases rotor rpm?

Answer 15

Flare phase

Question 16

Describe the stall region of the main rotor blade during autorotation.

Answer 16

Provides a decelerative force

• Includes the inboard 25%
• Operates above stall AOA
• Causes drag which tends to slow the rotation of the blade

Question 17

What aerodynamic problem is found only in fully-articulated rotor systems?

Answer 17

Ground resonance

Question 18

What aerodynamic problem is usually caused by a pilot using an incorrect technique when taking off from a slope?

Answer 18

Dynamic rollover

Question 19

What aerodynamic force causes an aircraft to fly forward?

Answer 19

Thrust

Question 20

What term describes the upward sweep of main rotor blades caused by lift and centrifugal force?

Answer 20

Coning

Question 21

What flight control system controls the lateral and longitudinal movement of the helicopter?

Answer 21

Cyclic

Question 22

What is the first indication of retreating blade stall?

Answer 22

A noticeable vibration

Question 23

What type of rotor system is always a two-bladed system?

Answer 23

Semi-rigid

Question 24

What components of the total aerodynamic force on an airfoil act perpendicular to the relative wind?

Answer 24

Lift

Question 25

An ______ in lift will produce an increase in drag.

Answer 25

Increase

Question 26

What force tends to make rotating bodies move away from the center of rotation?

Answer 26

Centrifugal force

Question 27

What 2 factors increase blade efficiency while operating in ground effect?

Answer 27

Reducing Induced airflow

Reducing rotor tip vortices

Question 28

During an auto when the engines have disengaged from the rotor system, what force is used to sustain the rotor RPM so controlled flight can be continued to the ground?

Answer 28

Airflow during descent provides the energy to drive the rotor system.