Aerodynamics

Question 1

Profile drag is composed of:

Answer 1

Form drag and skin friction

Question 2

Profile drag is caused by:

Answer 2

The frictional resistance of the blade passing through the air

Question 3

Induced drag associated with:

Answer 3

The production of lift.

Question 4

Parasite drag is associated with:

Answer 4

Non-lifting surfaces.

Question 5

Profile drag _______ ________ with an increase in airspeed. (Increases/decreases)(gradually/exponentially)

Answer 5

Increases gradually

Question 6

Parasite drag _______ _______ as airspeed increases. (Increases/decreases)(gradually/exponentially)

Answer 6

Increases exponentially.

Question 7

Induced drag _______ _______ as airspeed increases.

Answer 7

Decreases exponentially

Question 8

_____________ is the term used to describe the left-drifting tendency of the helicopter in a hover. What causes this?

Answer 8

Translating tendency. Caused by left pull of tail rotor to counteract the counterclockwise yaw created by the main rotor. (Need to pull the nose right, tail drifts left.)

Question 9

Due to the helicopter hovering with the CG located beneath the rotation axis (rotor hub), __________ causes the aircraft to “swing through” any accelerative changes.

Answer 9

Pendular action

Question 10

As centrifugal force pulls the rotors straight away from the hub and weight simultaneously acts on the hub, ______ occurs to the rotor arc. This increases/decreases with weight or blade loading.

Answer 10

Coning: increases.

Question 11

The accelerative increase and decrease in rotation as the blades flap is a phenomenon known as ________.

Answer 11

The Coriolis Effect

Question 12

Ground effect occurs within _______ of the surface and results in _______.

Answer 12

One rotor diameter of the surface

Results in an increase in rotor efficiency due to a decrease in induced flow.

Question 13

___________ causes forces acting on the rotor to be “felt” 90 degrees later. Unless counteracted by smoothly applying forward cyclic, this will result in _______.

Answer 13

Gyroscopic Precession.

Blowback.

Question 14

Translational lift causes an increase in rotor efficiency at approximately _______ KIAS.

Answer 14

16-24 KIAS

Question 15

As you pass through ETL, airflow over the vertical stabilizer becomes less turbulent, resulting in increased lift across the tail. Combined with the increase of main rotor efficiency, this causes a resultant _________ motion and must be compensated for with _________.

Answer 15

Right yaw.

Must be compensated for with an increase in left pedal.

Question 16

The change in relative speed as the blade rotates through the air in forward flight results in _________ and would cause the aircraft to tumble immediately if not corrected for by _________.

Answer 16

Dissymmetry of Lift.

Flapping.

Question 17

Factors that contribute to ULY:

Answer 17

WE MAY LOSE LEFT CONTROL PHLLL
Weathercock stability
Main rotor/tail rotor interaction
Loss of translational lift
Left crosswinds
Collective induced high yaw rates

Question 18

Flights regimes susceptible to ULY are:

Answer 18

PHLLL

Pilot induced high yaw rates
Hovering pedal turns, tail through the wind line
Low pedal margin maneuvers
Low speed left downwind turns
Left sideward flight

Question 19

Regarding the blade element diagram, _________ acts perpendicular to relative wind.

Answer 19

Total lift

Question 20

Regarding the blade element diagram, the angle formed by the chord line and the tip path plane or reference plane is known as the __________.

Answer 20

Pitch angle.

Question 21

The angle of attack is the angle formed by the _________ and the _________.

Answer 21

Relative wind and the chord line.

Question 22

The three types of drag are:

Answer 22

Profile
Induced
Parasite