Aerodynamics

Question 1

Difference in lift between the advancing and retreating blades

Answer 1

Dissymmetry of lift

Question 2

Advancing blade in flight has more _______ and thus more lift than the retreating blade

Answer 2

relative airspeed

Question 3

_______ Airflow flows from trailing edge to leading edge and produces no lift

Answer 3

Reverse

Question 4

________ Occurs when advancing blade flaps up while retreating blade flaps down

Answer 4

Blade flapping

Question 5

AOA

Answer 5

Angle of attack

Question 6

_________ Occurs when the pilot inputs forward cyclic which results in increasing pitch at 9 o’clock and decreasing pitch at 3 o’clock

Answer 6

Cyclic feathering

Question 7

What two things compensate for dissymmetry of lift?
1)
2)

Answer 7

1) Blade flapping
2) Cyclic feathering

Question 8

_______ is an action that presents itself 90 degrees later in rotation

Answer 8

Gyroscopic Precession

Question 9

The difference in lift, drag, and induced flow that exists between the forward and aft half of the rotor system 10-20 knots

Answer 9

Transverse Flow

Question 10

During ___________ airflow is more _________ and more _______of the rotor disk.

Answer 10

Transverse flow
Horizontal over the front half
Vertical over the rear half

Question 11

There is a higher _____ and power required for helicopters to hover OGE compared to IGE due to induced flow

Answer 11

Area of Incidence (AOI)

Question 12

___________ is the increase in lift that occurs when hovering within one rotor diameter above the surface.

Answer 12

Ground effect

Question 13

During IGE ________ develop around the rotor tips

Answer 13

Vortices

Question 14

During OGE there is a __________ and wing tip vortices are not restricted

Answer 14

High velocity of induced flow

Question 15

Is more power required during OGE or IGE hover?

Answer 15

OGE

Question 16

ETL

Answer 16

Effective Translational Lift

Question 17

ETL occurs between _________ Knots and is the point at which the rotor system _______________

Answer 17

16-24 Knots
Outruns the recirculation of vortices

Question 18

Past ETL the rotor begins to _________ producing lift more efficiently

Answer 18

operate in clean, undisturbed air

Question 19

During ETL, the main rotor becomes more efficient and ___________ for lift

Answer 19

less torque is required

Question 20

How can you tell when the ETL point is at during a hover?

Answer 20

where rotor wash ends

Question 21

At _______ knots, the helicopter is operating in its own recirculated air

Answer 21

0 knots

Question 22

________ or torque effect is the tendency for helicopters to drift laterally from tail rotor thrust at a hover

Answer 22

Translating Tendency

Question 23

What compensates for translating tendency?

Answer 23

Control Rigging
FMC
Pilot inputs

Question 24

A condition where a rotor system has a secondary set of vortices in addition to the wing tip vortices

Answer 24

Vortex ring state

Question 25

What is created by vortex ring state?

Answer 25

Highly disturbed/turbulent airflow

Question 26

3 requirements to get into VRS (Vortex ring state) 1) 2) 3)

Answer 26

1) Airspeed300 FPM Descent 3) 20-100% power applied

Question 27

VRS can cause ________ meaning helicopter descends despite having necessary power applied

Answer 27

Settling with power

Question 28

Name flight conditions that are conducive to VRS

Answer 28

- Steep Approaches - Downwind/Tail wind approaches - Poor altitude control at OGE hover - Hover above max ceiling - Descent from OGE Hover - Formation Approaches

Question 29

Point at which helicopter will roll over despite pilot inputs

Answer 29

Dynamic Rollover

Question 30

3 Requirements for Dynamic Rollover

Answer 30

1) Pivot point 2) Rolling Motion 3) Exceeding critical angle

Question 31

Name physical contributing factors of Dynamic Rollover

Answer 31

- Main/tail rotor thrust vectors - Asymmetric center of gravity - Crosswind effect on tail rotor - Ground surface conditions

Question 32

Name human contributing factors of dynamic roll over

Answer 32

- Inattentiveness - Inexperience - Inappropriate inputs - Slow corrective inputs - Loss of visual reference

Question 33

3 Types of drag

Answer 33

1) Parasite drag 2) Profile drag 3) Induced drag

Question 34

_______ Force that opposes or resists the motion of an object as it travels through the air

Answer 34

Drag

Question 35

All 3 types of drag together equal _____

Answer 35

Total drag

Question 36

_________ increases exponentially with airspeed

Answer 36

Parasite drag

Question 37

_________ air resistance on an object as it moves, increases with surface area

Answer 37

Parasite drag

Question 38

_________ caused by the frictional resistance of the blades as they travel through the air (lifting components) (Shape and skin friction)

Answer 38

Profile drag

Question 39

________ increases gradually with airspeed

Answer 39

Profile drag

Question 40

Type of drag that results of producing lift, high with higher AOA

Answer 40

Induced drag

Question 41

__________ decreases drastically with airspeed

Answer 41

Induced drag

Question 42

________ principle: An airfoils camber causes airflow to accelerate over the upper surface. The airflow travels faster on top of the airfoil than the bottom resulting on lower pressure on top.

Answer 42

Bernoulli's principle

Question 43

_____________ an airfoil acting at an angle relative to the wind pushes the air down and the airfoil up based on the premise of Newton's action/reaction

Answer 43

Newton's 3rd law of motion

Question 44

How is the AOI controlled?

Answer 44

Pilots control AOI with cyclic and collective inputs adjusting the mechanical angle

Question 45

_______ is an aerodynamic angle which is a product of AOI and induced flow

Answer 45

AOA (angle of attack)

Question 46

With high enough airspeed, the retreating blade can enter a stall condition that could result in temporary loss of control, this is called_______

Answer 46

Retreating Blade stall

Question 47

Causes of retreating blade stall

Answer 47

-Excessively high airspeed -Low rotor RPM -Too much forward cyclic -Excessively high collective angle

Question 48

Symptoms of Retreating blade stall

Answer 48

-Vibrations -Pitching up -Roll left

Question 49

Recovery of retreating blade stall

Answer 49

- Lower collective, reducing AOA -Reduce maneuver

Question 50

_________ uncommanded, rapid yaw rate that does not subside of its own accord. Can result in loss of control

Answer 50

LTE (loss of tail rotor effectiveness)

Question 51

Wind from 4 o'clock-8 o'clock position

Answer 51

Weathercock stability

Question 52

Wind from 8 o'clock-11 o'clock

Answer 52

Tail rotor vortex ring state

Question 53

Wind from 9 o'clock-11 o'clock

Answer 53

Main rotor disk vortex/interference

Question 54

Wind from 2 o'clock and 4 o'clock position

Answer 54

AOA reduction

Question 55

The best recovery technique for LTE

Answer 55

Apply forward cyclic while applying as much pedal input as possible to maintain heading control If altitude permits, collective reduction can aid in reducing the yaw rate

Question 56

Airspeed range providing the best power margin for maneuvering flight.

Answer 56

Bucket speed