Theory of Rotor Wing Flight Exam (copy)

Torque effect is an example of which newtons laws

Action/ reaction

More power is needed to obtain a desired RPM than is needed to maintain the RPM is which newton law

Inertia

Greater load, less acceleration is which newton law

Acceleration

If the airflow atop of the airfoil increases, static pressure will _____ and dynamic pressure will _____

Decrease, increase

Define center of pressure

The point along the cord line of an air foil to reach. All aerodynamic forces are considered to act.

Define airfoil

Any surface designed to produce lift when air is passed over it

What are 2 basic types of of airfoils?

Symmetrical and Non-symmetrical

Description of airfoil:

Rounded edge

Leading edge

Description of airfoil:

Straight line from the leading edge to to trailing edge

Chord

Description of airfoil:

Upper curvature

Upper camber

Description of airfoil:

Lower shape

Lower camber

Description of airfoil:

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

Span

Description of airfoil:

Tapered edge

Trailing edge

Define rotational relative wind as applied to an airfoil

The flow of air parallel to an opposite the flight path of an air foil.

Define induced flow

Downward flow of air through the rotor blades

Define resultant relative wind

Rotational relative when modified by induced flow

How is the angle of incidence measured in a rotary wing aircraft?

The angle between the cord line of an air foil in the plane of rotation (tip path plane)

Define angle of attack

The angle between the cord line of an air foil and the resultant relative wind

Which flight control changes the angle of incidence differently around the rotor system

Cyclic pitch control

With an increase in the speed of air over a surface, What happens to dynamic and static pressure?

Dynamic increases and static decreases

List the two components of total aerodynamic force

Lift and drag

Describe the relationship of lift to resultant relative wind

Perpendicular

Describe the relationship between drag and resultant relative wind

Drag is parallel to, and in the same direction of the resultant relative wind

What type of drag is:

Rotor tip vortices

Induced

What type of drag is:

Lift and total aerodynamic force titling reward on the airfoil

Induced

What type of drag is:

Skin friction on the fuselage

Parasite

What type of drag is:

Skin friction on the airfoil

Profile

What type of drag is:

Non-streamlined fuselage

Parasite

What type of drag decreases with an increase in airspeed?

Induced drag

Which type of drag increases with an increase in airspeed

Parasite drag

Define dissymmetry of lift

Differential (unequal) lift between between advancing and retreating halves of the rotor disk

Relative wind velocity on the advancing blade equals blade speed ______ airspeed

Plus (+)

Relative wind velocity on the retreating blade equals blade speed ____ airspeed

Minus (-)

What causes the advancing blade to flap up?

An increase in lift

What causes the retreating blade to flap down?

A decrease in lift

How does the helicopter compensate for dissymmetry of lift?

Flapping

How does the pilot control the dissymmetry of Lift?

Cyclic feathering

Define blowback

Change in attitude of the rotor system

How does the pilot correct for blowback?

Cyclic feathering

Which forces in the lift equation can the pilot control?

Coefficient of lift (CL) through angle of attack, and relative wind velocity or airspeed (V2)

What are the three factors in air density (1/2 rho) that will affect lift

Pressure, temperature, humidity

A semi rigid disk tilt relative to _____

Mast

An articulated disk tilt relative to the_______

Hub

Define centrifugal force

Outward force produced whenever a body moves in a curved path

Define rotor blade conning

Upward flexing of the rotor blades

Rotor blade conning is a compromise between which two forces

Lift and centrifugal force

Define gyroscopic procession

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

Why is blade twisting necessary?

To distribute the lifting force more evenly along the blade

A pedal turn to the right requires ______ Power than a pedal turn to the left

Less

Define translating tendency

Tendency of a single rotor helicopter to drift right while hovering

List four methods used to overcome, translating, tendency and single rotor helicopters

1. Rigging the cyclic

2. Tilting the mast

3. Left cyclic

4. Automatic flight control/stabilization argumentation system

List the four rotor blade actions

1. Rotation

2. Flapping

3. Feathering

4. Hunting

Describe the relationship of total force to the tip path plane

Perpendicular

When the rotor disk is tilted, what are the two components of total force?

Lift and thrust

What are the two flight conditions?

Balanced and unbalanced

At what altitude would the aircraft be in ground effect?

Less than one rotor diameter

Loss, or apparent loss, of ground effect is caused by?

1. An altitude greater than one rotor diameter

2. Trees and bushes

3. Tall grass and uneven terrain

4. Hovering over water

5. Beginning of translational movement

6. Hovering into wind

Define effective translational lift (ETL)

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

Effective translational lift occurs at an airspeed of

14-24kts

Transverse flow effect is noticeable at an airspeed of

10-20 kts

#1

Tip path plane

#2

Chord line

#3

Axis of rotation

#4

Rotational relative wind

#5

Induced flow

#6

Angle of attack

#7

Resultant relative wind

#8

Angle of incidence

#9

Lift

#10

Drag

#11

TAF (resultant force)

Define settling with power?

A condition of powered flight in which the helicopter settles and its own downwash

List the three simultaneous conditions required for settling with power

1. Vertical or near vertical descent of at least 300 feet per minute

2. 20% to 100% engine power

3. Slow airspeed less than ETL

List the required discovery procedures for settling with power

1. Increase airspeed with cyclic

2. Reduce collective as altitude permits

3. Adjust rotor RPM to normal operating range

Define autorotation

The flight condition during which no engine power is supplied, and he main rotor is driven only by the action of the relative wind

Describe how a pilot prevents a rotor RPM over speed during an auto rotation with turn

Collective control (increase)

List the three conditions required for dynamic rollover to occur

1. Pivot point

2. Rolling motion

3. Exceed critical angle

Dynamic rollover occurs due to a combination of which two factors

Physical and human factors

Which control input is required to recover from dynamic rollover on level ground

Smooth, moderate collective reduction

Operating at what speed is most likely to produce retreating blade stall

High forward speed

Describe the symptoms of retreating blade stall in a single rotor helicopter

1. Abnormal vibrations

2. Pitch up of the nose

3. Left roll

4. Loss of control (If corrective action is not applied)

Describe the recovery procedure from retreating blade stall

1. Reduce collective pitch

2. Regain control of aircraft

3. Reduce speed

4. Increase rotor RPM to normal operating range

5. Minimize maneuvering

6. Descend to a lower altitude