Block 2 Rotary Wing Aerodynamics

Question 1

__________ of helicopters and airplanes are basically the same, while __________ __________ differ widely from those of an airplane.

Answer 1

Aerodynamics

Flight Characteristics

Question 2

_________ ____ _________(___________) depends on the magnitude of the unbalanced force and mass of the body

Answer 2

Rate of change (acceleration)

Question 3

____________ provides the basis for all helicopters flight- vertical, forward, backward, sideward or hovering

Answer 3

Rotary Wing Aerodynamics - Balance of Forces

Question 4

Total force generated by a rotor system is always _____________ to the tip-path plane.

Answer 4

Perpendicular

Question 5

Force is divided into what two components?

Answer 5

lift and thrust

Question 6

The ________ component of a rotary wing aircraft acts horizontally to accelerate or decelerate the helicopter in the desired direction

Answer 6

Lift

Question 7

On a rotary wing aircraft, thrust may be directed in the desired direction by…

Answer 7

tilting the tip-path plane

Question 8

At __________, all opposing forces are in balance and the helicopter remains stationary

Answer 8

hover

Question 9

At hover, total force is acting opposite to the helicopter’s ________

Answer 9

weight

Question 10

To move a helicopter in some direction, a ________ must be applied to cause an _________ __________

Answer 10

force

unbalanced condition

Question 11

The wind produced by the rotational velocity of the rotor blade, induced flow caused by the production of lift and the movement of the helicopter through the air mass is:

Answer 11

Relative Wind

Question 12

Relative Wind is produced by:

Answer 12

1. The rotational velocity of the rotor blade
2. Induced flow caused by the production of lift
3. The movement of the helicopter through the air mass

Question 13

Relative wind moves in a ________, but __________ direction to the airfoil

Answer 13

Parallel

Opposite

Question 14

When a helicopter maintains a constant position over a selected point, usually a few feet above the ground

Answer 14

Hovering

Question 15

Rotor tip vortex is also known as:

Answer 15

Air swirl at the tip of the rotor blades

Question 16

There are high-power requirements for hovering due to:

Answer 16

The continuous creation of new vortexes and ingestion of existing vortexes

Question 17

A condition of improved performance encountered when operating near the ground

Answer 17

In-ground effect

Question 18

The reduction of the velocity of the induced air flow

Answer 18

Distinct phenomena 1

Question 19

Distinct phenomena 2

Answer 19

Reduction of the rotor tip vortex

Question 20

Type of hover in which the rotor blades move large volumes of air in a downward direction called induced flow.

Answer 20

Out-of-ground effect hover

Question 21

Out -of-ground effect hover requires a ______ _______ setting

Answer 21

high power

Question 22

A single-rotor helicopter has the tendency to drift laterally to the ______ during hover

Answer 22

right

Question 23

The tendency of a single-rotor helicopter to drift laterally to the right during hover.

Answer 23

Translating tendency

Question 24

Lateral tilt results in a main rotor force to the ______ that compensates for the tail rotor thrust to the ______

Answer 24

left

right

Question 25

As the incoming wind enters the rotor system, turbulence and vortexes are left behind, the flow of air becomes more horizontal, improving performance.

Answer 25

Transitional lift

Question 26

When a helicopter transitions from hover to ________ _______, the tail rotor becomes more aerodynamically efficient.

Answer 26

forward flight

Question 27

During transitional lift, __________ increases due to the tail rotor working in progressively less turbulent air as speed is increased.

Answer 27

efficiency

Question 28

During transitional lift, more thrust is produced causing the aircraft's nose to _______ _______ due to the main rotor turning __________________

Answer 28

yaw left | counterclockwise

Question 29

During a helicopter takeoff, the _________ _________ must be applied as speed increases to correct for left yaw tendency

Answer 29

right pedal

Question 30

The difference in lift between the advancing half of the rotor disk and the retreating half

Answer 30

Dissymmetry of lift

Question 31

During dissymmetry of lift, the blade passing the tail and advancing reaches a maximum at the ________ position

Answer 31

3 o'clock

Question 32

During dissymmetry of lift, the blade speed decreases and reaches a minimum airspeed at the _________ position

Answer 32

9 o'clock

Question 33

Downward force applied at point A results in downward movement response at point B, and upward force applied at point C results in upward response movement at point D. This is called:

Answer 33

Gyroscopic precession (refer to figure 2-20)

Question 34

___________ affects the rotor disk when force is applied at a given point

Answer 34

(gyroscopic) precession

Question 35

The rotor will always tilt in the direction in which the _______ ________ is moved.

Answer 35

cyclic stick

Question 36

When the engine fails or is disengaged from the rotor system, a ______ must be used to sustain rotor RPM so controlled flight can be continued to the ground.

Answer 36

force

Question 37

During autorotation, the pilot gives up __________ at a controlled rate in return for _________ to turn the rotor at an RPM that provides aircraft control

Answer 37

altitude | energy

Question 38

When an engine fails or is disengaged from the rotor system, a force must be used to sustain rotor RPM so controlled flight can be continued to the ground.

Answer 38

Autorotation

Question 39

During autorotation, as altitude decreases, ________ _________ is converted to __________ __________ and stored in the turning rotor

Answer 39

potential energy | kinetic energy

Question 40

During autorotation, the pilot uses _______ _______ to cushion the touchdown when nearing the ground

Answer 40

kinetic energy

Question 41

Entry into ______________ is performed following loss of engine power

Answer 41

autorotation

Question 42

Indications of power loss are:

Answer 42

Rotor RPM decay and an out-of-trim condition

Question 43

During entry into autorotation, establish a _________ at the proper airspeed depending on the helicopter and its gross weight. RPM should be stabilized.

Answer 43

glide

Question 44

Autorotation RPM is a _______ _______ _________ than normal operating RPM

Answer 44

few turns higher

Question 45

Rate of descent and RPM are stabilized and the helicopter descends at a constant angle. This is called:

Answer 45

steady-state descent

Question 46

During steady-state descent, the angle of attack descent is normally

Answer 46

17 to 20 degrees

Question 47

Steady-state descent depends on the following 5 things:

Answer 47

``` airspeed density altitude wind helicopter ```

Question 48

To successfully perform an autorotative landing, reduce ________ and ____________ just before touchdown

Answer 48

airspeed | rate of descent

Question 49

During deceleration and landing during autorotation, __________ change inclines the total force of the rotor disk.

Answer 49

attitude

Question 50

During deceleration and landing in autorotation, blade _______ ______ is available to cushion the touchdown

Answer 50

kinetic energy

Question 51

During autorotation deceleration and landing, _______ ________ is applied to cushion the touchdown.

Answer 51

collective pitch

Question 52

Newton's law of action and reaction, states that a helicopter fuselage tends to rotate in the direction ___________ the rotor blades

Answer 52

opposite

Question 53

_______ must be counteracted and/or controlled before flight is possible

Answer 53

Torque

Question 54

_______ results from the rotor's being driven by the engine power output

Answer 54

Torque

Question 55

Torque effect must be __________ corrected

Answer 55

continually

Question 56

Torque effect rotates the fuselage in a direction opposite the main rotor and the tail rotor counteracts torque effect and provides positive fuselage heading control. This is identified as:

Answer 56

Anti-torque rotor

Question 57

An anti-torque rotor compensates for torque in the single main rotor helicopter. This is done by the _____ _______

Answer 57

tail rotor

Question 58

An anti-torque rotor produces thrust in a horizontal plane ________ to torque reaction developed by the main rotor.

Answer 58

opposite

Question 59

_________ compensate for torque variance

Answer 59

Pedals

Question 60

____ to ____ percent of the available engine power may be needed to drive the tail rotor

Answer 60

5 to 15

Question 61

The up and down movement of rotor blades is known as:

Answer 61

Blade flapping

Question 62

During blade flapping, the blade climbs or flaps upward, from change in ______ ______ and ______ ___ _______ which reduces the amount of lift that would have been generated

Answer 62

relative wind | angle of attack

Question 63

During blade flapping, as the blade loses airspeed, reducing lift causes it to settle or flap _________, thus changing its relative wind and angle of attack

Answer 63

downward

Question 64

The retreating blade must produce an amount of lift equal to that of the __________ _______

Answer 64

advancing blade

Question 65

As the speed of the retreating blade decreases with forward speed, blade angle of attack must be increased to equalize _______ throughout the rotor disk area

Answer 65

lift

Question 66

Conditions most likely to produce blade stall:

Answer 66

``` High blade loading (high gross weight) Low rotor RPM High-density altitude Steep or abrupt turns Turbulent air ```

Question 67

Warnings of approaching retreating blade stall:

Answer 67

Abnormal vibration (shuddering) Pitch up of the nose Tendency for the helicopter to roll in the direction of the stalled stick

Question 68

To prevent blade stall, the helicopter must fly slower than normal when:

Answer 68

The density altitude is much higher than standard Carrying maximum gross loads Flying high-drag configurations, external stores, weapons, sling loads, etc. The air is turbulent

Question 69

Procedures for correcting blade stall:

Answer 69

Decrease collective pitch Decrease the severity of the maneuver Gradually decrease airspeed Increase rotor RPM

Question 70

In a severe blade stall, ______ _________ ___ ______

Answer 70

all control is lost

Question 71

Fully articulated rotors are free to move ______ and _____ in the plane of rotation independent

Answer 71

fore | aft

Question 72

Pitch angle variation causes changes in the blade drag which makes the blade _________ or _______ about the drag hinge

Answer 72

lead | lag

Question 73

This law states that a rotating body will continue to rotate with the some rotational velocity until some external force is applied to change the speed of rotation

Answer 73

Coriolis Force

Question 74

Blade lead and lag is governed by the law of:

Answer 74

Conservation of angular momentum

Question 75

Applying the principle of Coriolis force to a rotating helicopter blade, it may be stated:

Answer 75

1. A mass moving radially outward on a rotating disk exerts a force opposite to rotation (decelerates) 2. A mass moving radially inward on a rotating disk exerts a force in the direction of rotation (acceleration)

Question 76

__________ _____ ________ happens at high altitudes, at high gross weights, or when operating with reduced power

Answer 76

Settling with power

Question 77

Settling with power makes __________ flight possible

Answer 77

level

Question 78

Settling with power can occur at any _______ or ______ , when power required exceeds power available

Answer 78

airspeed | altitude

Question 79

Settling with power, preventing level flight at _______ ________

Answer 79

slower speeds

Question 80

An extremely critical situation that may develop at any altitude or gross weight when the airspeed is below translational lift and rate of descent is high

Answer 80

Vortex ring state

Question 81

During vortex ring state, down wash from the rotor begins to recirculate up, around and back down through the effective outer portion of the _______ _____

Answer 81

rotor disc

Question 82

During vortex ring state, ________ and ________ ____ ___ ________ may occur

Answer 82

roughness | partial loss of control

Question 83

How do you recover from vortex ring state

Answer 83

Increase forward air speed, decrease collective pitch or enter autorotation if altitude permits