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Private Pilot Helicopter - R22 > Aerodynamics Of Flight > Flashcards

Flashcards in Aerodynamics Of Flight Deck (25)
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1
Q

What are the four forces acting on the helicopter?

A

Thrust, Drag, Weight, Lift

2
Q

What are the three types of drag?

A

Profile drag, induced drag, parasite drag - PIP

3
Q

What is profile drag?

A

Frictional resistance of the blades passing through the air

4
Q

What is induced drag?

A

The component of lift that is acting in a rearward direction generated by the airflow around the rotor blade as it creates lift.

5
Q

What is parasite drag?

A

Drag caused by the non-lifting components of the helicopter such as the cabin, rotor mast, tail, and landing gear.

6
Q

What is induced flow?

A

The downward flow of air through the rotor disk.

7
Q

What is the resultant relative wind?

A

Relative wind modified by induced flow

8
Q

What is the angle of attack?

A

Angle measured between the resultant relative wind and the chord line of the rotor.

9
Q

What is the angle of incidence?

A

The angle between the chord line of a blade and the rotor hub. Also known as blade pitch angle.

10
Q

Is the angle of incidence mechanical or aerodynamic?

A

Mechanical

11
Q

Is the angle of attack aerodynamic or mechanical?

A

Aerodynamic

12
Q

What changes the angle of incidence?

A

Collective input and cyclic feathering

13
Q

What is the translating tendency?

A

The tendency of the helicopter to move in the direction of the tail rotor thrust in hovering flight.

14
Q

How is the translating tendency counteracted?

A
  1. Main transmission is mounted at slight angle to the left.

2. Flight controls can be rigged so the rotor disk is tilted to the left slightly when the cyclic is centered.

15
Q

What is the danger of rearward flight?

A

The horizontal stabilizer can press the tail downward resulting in tail strike if the helicopter is moved into the wind.

16
Q

What is coning?

A

Rotation of the rotor system creates centrifugal force which tends to pull the blades straight outward from the main rotor hub. The faster the motion the greater the centrifugal force. This forces gives the rotor blades their rigidity and strength to support the weight of the helicopter. Blade assumes a conical path instead of remaining perpendicular.

17
Q

What is the danger if the rotor RPM is allowed to go too low?

A

Should they decrease too much the rotor blades would fold up with no chance for recovery.

18
Q

What is the Coriolis Effect?

A

Also known as the Law of Conservation of Angular Momentum. Rotating body continues to rotate with the same rotational velocity until some external force is applied to change the speed of the rotation.

19
Q

What is gyroscopic precession?

A

The resultant action or deflection of a spinning object when a force is applied to this object which occurs approximately 90 degrees in the direction of rotation from the point where the force is applied.

20
Q

What is dissymmetry of lift?

A

The differential (unequal) lift between advancing and retreating halves of the rotor disk caused by the different wind flow velocity across each half

21
Q

What is retreating blade stall?

A

When the critical angle of attack is reached on the retreating blade.

22
Q

What is evidence of retreating blade stall?

A

Nose pitch up, vibration, and a rolling tendency usually to the left.

23
Q

What is translational lift?

A

Improved rotor efficiency resulting from directional flight?

24
Q

What is effective translational lift (ETL)?

A

Between 16 and 24 kts, the rotor system completely outruns the recirculation of old vortices and begins to work in relatively undisturbed air. Flow through the air is more horizontal

25
Q

What is the transverse flow effect?

A

As the helicopter accelerates in forward flight, induced flow drops to near zero at the forward disk area and increases at the aft disk area. The result is a tendency for the helicopter to roll slightly to the right as it accelerates through approximately 20 kts.