Theory Of Rotary Wing Flight Flashcards by William Kilson

Newton’s Laws of Motion(which law is involved)

Torque Effect

action/reaction

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Newton’s Laws of Motion(which law is involved)

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

Inertia

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Newton’s Laws of Motion(which law is involved)

Greater load, less acceleration

Acceleration

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If the airflow atop the airfoil increases, static pressure will

decrease

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If the airflow atop the airfoil increases, dynamic pressure will

increase

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Center of Pressure

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

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Airfoil

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

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Basic types of airfoils

Symmetrical

Unsymmetrical or Nonsymmetrical

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Airfoil terms

Chord
Upper camber
Lower camber
Span
Trailing edge
Leading edge

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Chord

Straight line from the leading edge to the trailing edge

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Upper camber

Upper curvature

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Lower camber

Lower shape

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Span

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

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Trailing edge

Tapered edge

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Leading edge

Rounded edge

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Rotational relative wind (as applied to an airfoil)

That flow of air parallel and path of an opposite to the flight path of an airfoil

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Induced flow

Downward flow of air through the rotor blades

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Resultant relative wind

Rotational relative wind modified by induced flow

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

The angle between the chord of an airfoil and the plane of rotation (tip path plane)

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Angle of attack

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

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Which flight control changes the angle of incidence differentially around the rotor system?

Cyclic pitch control

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

Dynamic pressure increases, static pressure decreases

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Components of total aerodynamic force

Lift and drag

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Describe the relationship of lift to resultant relative wind

Perpendicular

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Relationship between drag and resultant relative wind

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

Rotor-tip vortices

induced

Lift and total aerodynamic force tilting rearward on the airfoil

induced

Skin friction on the fuselage

parasitic

Skin friction on the airfoiil

profile

Non-streamlined fuselage

parasitic

Which type of drag decreases with an increase in airspeed?

Induced

Which type of drag increases with an increase in airspeed?

parasite

Dissymmetry of lift

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

Relative wind velocity on the advancing blade equals blade speed...

plus airspeed

Relative wind velocity on the retreating blade equals blade speed...

minus airspeed

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 dissymetry of lift?

cyclic feathering

Blowback

Change in the 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 and airspeed

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

pressure, temperature, and humidity

A semi-rigid disk tilts relative to the

mast

An articulated disk tilts relative to the

hub

Centrifugal force

Outward force produced whenever a body moves in a curved path

Rotor blade coning

Upward flexing of the rotor blades

Rotor blade coning is a compromise between which two forces

lift and centrifugal force

gyroscopic precession

When a force is applied to a rotating body, it will manifest 90 degrees 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 ____(more/less) power than a pedal turn to the left

less

Translating tendency

Tendency of a single rotor helicopter to drift right while hovering

List four methods used to overcome translating tendency in single rotor helicopters

rigging the cyclic tilting the mast left cyclic

List the four rotor blade actions

rotation flapping feathering 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 effects

One rotor disc diameter measured from the rotor disc to the surface

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

a. An altitude greater than one rotor diameter b. Trees and bushes c. Tail grass and uneven terrain d. Hovering over water e. Beginning of translational movement f. Hovering into a wind

Translational lift

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

Effective translational lift occurs at an airspeed of

Approximately 16-24 KTS

Transverse flow effect is noticeable at an airspeed

10-20 KT

Settling with power

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

List three simultaneous conditions required for settling with power

Vertical or near vertical descent of at least 300 FPM 20% to 100% engine power Slow airspeed less than ETL

List the required recovery procedures for settling with power

Increase airspeed with cyclic Reduce collective as altitude permits Adjust rotor RPM to normal operating range

Autorotation

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

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

The pilot must prevent rotor RPM over speed with collective control

List the three conditions required for dynamic rollover to occur

Pivot point Rolling motion Exceed critical angle

Dynamic rollover occurs due to a combination of which two factors?

Physical and human

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

Abnormal vibration, pitch-up of the nose, and left roll

Describe the recovery procedure from retreating blade stall

Reduce collective pitch, regain control of the aircraft, reduce airspeed, increase rotor RPM to normal operation range, minimizing maneuvering, and descend to a lower altitude

Theory Of Rotary Wing Flight Flashcards

(73 cards)