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Helicopter Theory > Aerodynamic Forces > Flashcards

Aerodynamic Forces Flashcards

1
Q

The axis of rotation passes through the ________________________ and is always at (right angles / parallel) to the plane of rotation.

A
  • Rotor Head.
  • Right angles.
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2
Q

The disc area is the area contained within the ____________________ and in flight, the area (is / is not) constant because it is effected by the ___________________ angle.

A
  • Tip Path.
  • Is Not.
  • Coning.
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3
Q

Disc loading means the ________________ of the helicopter divided by the _____________ ___________.

A
  • Weight.
  • Disc Area.
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4
Q

Flapping means the movement of the blades in the (vertical / horizontal) sense relative to the (plane of rotation / axis of rotation).

A
  • Vertical.
  • Plane of Rotation.
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5
Q

Lead-Lag means the movement of the blade (forward & aft / up & down) in the (plane of rotation / tip path plane).

A
  • Forward & Aft.
  • Plane of Rotation.
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6
Q

The difference between a fully-articulated rotor and a semi-rigid rotor is that the latter (does / does not) allow for (feathering / lead & lagging) through hinge’s.

A
  • Does Not.
  • Leading & Lagging.
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7
Q

The semi-rigid rotor system is common with the (two / more than two) bladed rotors and (leading & lagging / flapping) is generally taken up within the blade or the blade attachment components.

A
  • Two.
  • Leading & Lagging.
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8
Q

The relative (or resulting) airflow that influences the rotor blade in forward flight is a combination of airflow due to ____________, ___________ ___________ & ______________ _____________.

A
  • Rotation.
  • Induced Flow.
  • Aircraft Speed
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9
Q

Airflow due to rotation (Vr) is (always / sometimes) in the (tip path plane / plane of rotation)

A
  • Always.
  • Plane of Rotation.
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10
Q

Induced flow means the airflow forced down by the rotors action (all of which / most of which passes through the rotors.

A
  • Most of which.
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11
Q

When the induced flow increases, the inflow angle (increases / decreases) and for a given blade angle and rotor RPM, the angle of attack will (increase / decrease).

A
  • Increase.
  • Decrease.
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12
Q

Rotor thrust is a (resultant / component) of the total reaction which (can / cannot) be perpendicular to the relative airflow.

A
  • Component.
  • Cannot.
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13
Q

Total rotor thrust always acts at (right angles to / in line with) the (shaft axis / axis of rotation).

A
  • In line with.
  • Axis of rotation.
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14
Q

The force that overcomes the gross weight of the helicopter is ________________or a component of that force.

A
  • Total Rotor Thrust.
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15
Q

Rotor drag is a force which acts in the (plane of rotation / relative airflow) and it acts to ( increase / decrease) rotor RPM.

A
  • Plane of Rotation.
  • Decrease Rotor RPM.
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16
Q

Assuming constant rotor RPM, when the inflow angle decreases and collective is lowered proportionally, the total rotor thrust / rotor drag ratio (improves / worsens) so that (more / less) power is required to maintain rotor RPM.

A
  • Improves.
  • Less.
17
Q

A rotor operates at its most efficient when the total rotor thrust / rotor drag ratio is at its (best / worst) and the collective lever is as (high / low) as possible.

A
  • Best.
  • Low.
18
Q

Compared to a cool dry day, On a hot and humid day the blade’s angle of attack needs to be (greater / smaller / the same) and the total rotor thrust / rotor drag ratio is (better / worse).

A
  • Greater.
  • Worse.
19
Q

With a constant rotor RPM, raising of the collective will (increase / decrease) the coning angle, total rotor drag will (increase / decrease) and the requirements for ______________ goes up.

A
  • Increase.
  • Increase.
  • Power.
20
Q

The advantage of the high-inertia rotor over the low-inertia rotor is that rotor RPM tends to fluctuate (more / less) and the flare is (easier / more difficult) to execute but recovery from low rotor RPM is achieved (quicker / less quickly).

A
  • Less.
  • Easier.
  • Less Quickly.

Helicopter Theory (9 decks)

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