Basic

Question 1

lift

Answer 1

perpendicular to relative wind regardless of attitude. Varies with airspeed, density, characteristics of airfoil, and AOA.

Question 2

weight

Answer 2

pull of gravity acts through C.G. straight down toward center of earth. only changes with changes in aircraft gross weight

Question 3

coning

Answer 3

helicopter blades rise above straight out position as they develop lift during takeoff and flight

Question 4

airfoil lift

Answer 4

increased speed causes increased lift at a square of the increase in speed. 500 knots has four times lift of blade traveling at 250 knots

Question 5

stall angle

Answer 5

point which airflow no longer follows the camber of the blade smoothly

Question 6

point of impact

Answer 6

point at which the air separates to flow about the airfoil

Question 7

where is the high pressure area or stagnation point formed in relation to the leading edge?

Answer 7

lower portion of the leading edge

Question 8

types of drag

Answer 8

profile- from friction
induced- from lift production
parasite- from stuff hanging off that doesn’t fly

Question 9

centrifugal vs centripetal

Answer 9

fugal- out from center

petal- counter fugal, keeps objects a certain radius from axis of rotation

Question 10

symmetrical airfoil cons

Answer 10

identical upper and lower
less lift produced than asymmetric
undesirable stall characteristics

Question 11

symmetrical airfoil pros

Answer 11

center of pressure remains constant
best lift drag ratios for full range of velocities from rotor blade root to tip
low cost / easy construction

Question 12

non-symmetrical airfoil

Answer 12

increased lift drag ratios
more desirable stall characteristics
twisting force exerted about center of pressure
center of pressure moves with aoa changes

Question 13

hover effect on blades

Answer 13

tip vortex reduces the effectiveness of outer blade portions and severely affect lift of the following blades

Question 14

primary cause of high power requirements for hovering

Answer 14

continuous creation of new vortices and ingestion of existing vortices

Question 15

translating tendency

Answer 15

lateral movement during hovering flight (tail rotor drift)

Question 16

ground effect occurs where?

Answer 16

one rotor diameter over a surface (up to 48ft)

Question 17

IGE v OGE power requirement

Answer 17

OGE is 30% > IGE

Question 18

IGE hover factors

Answer 18

reduction of downward velocity of induced airflow (ground gets in the way. Result is less induced drag and more vertical lift vector)

reduction of rotor tip vortex

Question 19

best IGE?

Answer 19

OVER SMOOTH PAVED SURFACES

Question 20

transverse flow effect

Answer 20

downward flow at rear of rotor disk results in less lift production than at front

Question 21

dissymmetry of lift

Answer 21

difference in lift between advancing half of rotor disk and the retreating half. advancing blade has more lift and wants to climb, retreating wants to drop

Question 22

feathering

Answer 22

mechanical change in angle of incidence or pitch of blade

Question 23

flapping

Answer 23

movement of rotor blades on an upward or downward path during rotation

Question 24

what causes nose to pitch up?

Answer 24

phase lag. right side is producing more lift than left side

Question 25

what does blade flapping eliminate?

Answer 25

dissymmetry of lift

Question 26

retreating blade stall

Answer 26

limits the maximum airspeed of helicopter

Question 27

translational lift

Answer 27

improved efficiency from directional flight; rotor becomes more efficient with airspeed

Question 28

effective translational lift

Answer 28

the point at which the ac outruns its own downwash; 16-24 knots

Question 29

phases of autorotation

Answer 29

entry, steady state descent, deceleration with touchdown

Question 30

describe entry phase of ar

Answer 30

transition from powered to unpowered flight

Question 31

describe steady-state descent

Answer 31

permits pilot to glide helicopter toward ground under controlled conditions

Question 32

deceleration with touchdown phase

Answer 32

pilot must reduce airspeed and rate of descent just before touchdown by flaring.

Question 33

most significant factor affecting rate of descent in an ar?

Answer 33

airspeed

Question 34

autorotative regions

Answer 34

stall region, driving region, driven region

Question 35

stall region

Answer 35

rotational relative wind is slow and resultant rw exceeds aoa. inner 25% of rotor disk.

Question 36

driving region

Answer 36

total aerodynamic force (taf) is tilted forward, driving the blade during ar. 25%-70% middle section of rotor disk.

Question 37

driven region

Answer 37

taf is tilted aft, producing lift but with more drag. 30% closest to tips.

Question 38

how to achieve constant rotor rpm

Answer 38

balance driving region with driven and stall regions

Question 39

what aerodynamic force causes forward flight?

Answer 39

thrust

Question 40

what term describes upward sweep of main rotor blades caused by lift and centrifugal force?

Answer 40

coning

Question 41

which force acts perpendicular to relative wind?

Answer 41

lift

Question 42

in a no wind condition, the tip path plane of the blades remains…

Answer 42

horizontal

Question 43

what two factors increase blade efficiency IGE?

Answer 43

reduction of velocity of induced airflow and reduction of rotor tip vortex

Question 44

during ar what force is used to sustain rotor rpm?

Answer 44

relative wind during descent