Rotary Wing Aerodynamic

Question 1

Newton’s third law which states

Answer 1

“every action has an equal and opposite reaction.”

Question 2

With the helicopter on the ground, rotors turning and with the collective full down, the rotor blades are referred to as

Answer 2

“flat pitch.”

Question 3

An imaginary line from the rotor blade leading edge to the trailing edge is called the

Answer 3

“chord line.”

Question 4

The ________ is perpendicular to the relative wind line.

Answer 4

lift vector

Question 5

A helicopter inflight creates a downward rotor wash. As a result, the relative wind is no longer horizontal but contains a downward component called

Answer 5

“induced flow.”

Question 6

_____________ is the drag incurred as a result of production of lift.

Answer 6

Induced drag

Question 7

An increase in temperature or humidity or a decrease in pressure will cause density to ________, thereby causing a _____ in lift.

Answer 7

decrease; decrease

Question 8

Increasing temperature results in ________ air density.

Answer 8

decreasing

Question 9

Compared to dry air, the density of air at 100% humidity is __________.

Answer 9

less dense

Question 10

The vertical down-flow of air through the rotor system is __________.

Answer 10

induced flow

Question 11

The collective pitch control, located on the left side of the Pilot’s seat __________.

Answer 11

changes the pitch angle of both main rotor blades simultaneously

Question 12

The anti-torque pedals, located on the cabin floor by the Pilot’s feet __________.

Answer 12

control the pitch, and therefore the thrust, of the tail rotor blades

Question 13

________ is a gain in lift obtained when an aircraft hovers near the ground within 1 RD of the surface.

Answer 13

Ground effect

Question 14

Ground effect reduces induced flow resulting in __________.

Answer 14

an increase in main rotor lift

Question 15

Ground effect occurs when the helicopter is within __________.

Answer 15

1 RD of the surface

Question 16

Improved rotor efficiency resulting from directional flight is called

Answer 16

translational lift.

Question 17

Translational lift occurs as the helicopter accelerates through __________.

Answer 17

16 to 24 knots

Question 18

As the helicopter flies through translational lift, it becomes more efficient because __________.

Answer 18

the rotor moves out of its vortices and is in relatively undisturbed air

Question 19

__________ is the difference in lift between advancing half and the retreating half of the main rotor system.

Answer 19

Dissymmetry of lift

Question 20

T/F:

As the relative wind speed of the advancing blade increases, the blade gains lift and begins to flap up.

Answer 20

True

Question 21

A factor which limits a helicopter’s forward speed is ___________.

Answer 21

retreating blade stall

Question 22

An indication of retreating blade stall is __________.

Answer 22

an increase in airframe vibration

Question 23

____________ is an uncommanded rate of descent caused by the aircraft rotor inducing a vortex ring as it settles into its own down wash.

Answer 23

Vortex ring state

Question 24

_________ is a descent caused by a maneuver where power required is greater than power available.

Answer 24

Settling with power

Question 25

When vortex ring state is evident, the condition may be eliminated by accomplishing one or a combination of the following corrective actions:

Answer 25

Reduce collective, apply forward cyclic to gain airspeed, and enter autorotation

Question 26

T/F: During all types of takeoffs and landings, the helicopter is susceptible to a lateral rolling tendency called dynamic rollover.

Answer 26

True

Question 27

Bank angles of as little as 5 degrees, coupled with a roll rate and crosswinds, can cause the aircraft to roll over in approximately __________ seconds.

Answer 27

2

Question 28

________ is a condition in which a rotor system is driven by relative wind rather than the engines. Lift being perpendicular to relative wind, in autorotation the lift force has a forward horizontal component (the driving force for the rotor system).

Answer 28

Autorotation

Question 29

Which is not an effect of the flare in an autorotational descent?

Answer 29

Increased tail rotor ground clearance

Question 30

What is the force providing rotor rpm during autorotation?

Answer 30

The horizontal component of lift