Helicopter Principles Flashcards by Neilbert Villaflor

Any surface designed to produce lift or thrust when air passes over it.

a. Airfoil
b. Chordline
c. Pitch Angle

a. Airfoil

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Imaginary straight line from the leading edge to the trailing edge.
Relative Wind Direction of the airflow with respect to the airfoil.

a. Airfoil
b. Chordline
c. Pitch Angle

b. Chordline

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Is the acute angle between the blade chordine and the rotor plane of
rotation.

a. Airfoil
b. Chordline
c. Pitch Angle

c. Pitch Angle

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Angle between the chordline and the direction of the relative wind.

d. Angle of Attack
e. Lift
f. Drag

d. Angle of Attack

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Differential pressure on the upper camber and lower camber.

d. Angle of Attack
e. Lift
f. Drag

e. Lift

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Force that resist movement of the airfoil through the air.

d. Angle of Attack
e. Lift
f. Drag

f. Drag

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When air can no longer flow smoothly over the top causing a large loss of
lift.

g. Stall
h. Lift and Angle of Attack
i. Lift and velocity of airflow

g. Stall

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Angle of attack increases – lift increases up to stall angle.

g. Stall
h. Lift and Angle of Attack
i. Lift and velocity of airflow

h. Lift and Angle of Attack

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Velocity increases, lift increases. In the helicopter the pilot
maintains a constant rotor rpm and changes lift by varying
the angle of attack.

g. Stall
h. Lift and Angle of Attack
i. Lift and velocity of airflow

i. Lift and velocity of airflow

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Lift varies directly with density of air.

j. Lift and air density
k. Thrust and Drag
l. Hovering flight

j. Lift and air density

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Thrust moves the aircraft in the desired direction; drag, the
retarding fore of inertial and wind resistance tends to hold it back.

j. Lift and air density
k. Thrust and Drag
l. Hovering flight

k. Thrust and Drag

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Tip path is horizontal that is, parallel to the ground. Lift and thrust
straight up, weight and drag down.

j. Lift and air density
k. Thrust and Drag
l. Hovering flight

l. Hovering flight

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Lift and thrust acts vertically; weight and drag acts vertically downward.

l. Hovering flight
m. Vertical flight
n. Forward flight

m. Vertical flight

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Tip path plane filled forward; thus tilting the total lift thrust force forward
from the vertical.

l. Hovering flight
m. Vertical flight
n. Forward flight

n. Forward flight

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Tip path plane is tilted sideward in the direction of flight.

o. Sideward flight
p. Rearward flight
q. Torque

o. Sideward flight

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Tip path plane is tilted rearward.

o. Sideward flight
p. Rearward flight
q. Torque

p. Rearward flight

Newton’s third law of motion – as the main rotors turn in one direction,
the fuselage to rotate in the opposite direction. This tendency of the
fuselage to rotate is called torque.

o. Sideward flight
p. Rearward flight
q. Torque

q. Torque

Compensate for torque.

r. Auxillary rotor
s. Gyroscopic Precession
t. Dissymmetry of lift

r. Auxillary rotor

The spinning main rotor act like a gyroscope. It is resultant action
or direction of a spinning object when a force is applied to the
object.

r. Auxillary rotor
s. Gyroscopic Precession
t. Dissymmetry of lift

s. Gyroscopic Precession

Area within the tip path plane of the main rotor is known as disc
area or rotor disc.

r. Auxillary rotor
s. Gyroscopic Precession
t. Dissymmetry of lift

t. Dissymmetry of lift

In a three bladed rotor system, the blades are attached to the hub
by a horizontal hinge which permits the blades to move in a
vertical plane. In a two bladed system, the blades flap as a unit. As
the advancing blade flaps up due to increase lift, the retreating
blade flaps down due to decrease lift.

u. Blade flapping
v. Axis of rotation
w. Corioli’s Effect

u. Blade flapping

Imaginary line about which the rotor rotates.

u. Blade flapping
v. Axis of rotation
w. Corioli’s Effect

v. Axis of rotation

In a three bladed rotor system when the blades flaps upward, the
distance of the center of the mass of the blade from the axis of
rotation decreases.

u. Blade flapping
v. Axis of rotation
w. Corioli’s Effect

w. Corioli’s Effect

The entire helicopter has a tendency to move in the
direction of the tail rotor thrust (to the right) when
hovering. This movement is known as drift.

x. Translating tendency or Drift
y. Ground Effect
z. Translation Lift

x. Translating tendency or Drift

When a helicopter is hovering, the rotor blades will be displacing air downward through the disc faster than it can escape from beneath the helicopter thus, building-up a cushion of denser air between the ground and the helicopter. x. Translating tendency or Drift y. Ground Effect z. Translation Lift

y. Ground Effect

Addition lift obtained when entering horizontal flight due to efficiency of the rotor system. x. Translating tendency or Drift y. Ground Effect z. Translation Lift

z. Translation Lift

The relative wind has a higher velocity at the rear portion of the rotor disc than at the forward portion. aa. Transverse Flow Effect bb. Pendular Action cc. Auto-rotation

aa. Transverse Flow Effect

Fuselage of the helicopter is suspended from a single point and has a considerable mass. It is free to oscillate either longitudinally or laterally in the same way as a pendulum. aa. Transverse Flow Effect bb. Pendular Action cc. Auto-rotation

bb. Pendular Action

Flight condition wherein no engine power is supplied and the main rotor is only driven by the relative wind. It is a means of safety landing the helicopter during engine failure or on certain emergencies. aa. Transverse Flow Effect bb. Pendular Action cc. Auto-rotation

cc. Auto-rotation

Rotor rpm stabilizes when the auto-rotative forces (thrust) of the driving region and the anti-rotative forces (drag) of the driven region and the stall regionare equal. dd. Rotor RPM during auto-rotation ee. Flares during auto-rotation ff. Lift components of a turn

dd. Rotor RPM during auto-rotation

Forward speed during auto-rotative descent permits the pilot incline the rotor disc rearward thus causing a flare. This flare permits the pilot to make an emergency landing roll or skid. dd. Rotor RPM during auto-rotation ee. Flares during auto-rotation ff. Lift components of a turn

ee. Flares during auto-rotation

Turn is produced by banking the helicopter thus allowing the lift of the rotor disc to pull the helicopter from its straight course. dd. Rotor RPM during auto-rotation ee. Flares during auto-rotation ff. Lift components of a turn

ff. Lift components of a turn

Heli strength is measured basically by the total load the rotor blades are capable of carrying without permanent damage. Loads imposed on the rotor blades depend largely on the type of flight. gg. Loads hh. Load Factor ii. Collective Pitch

gg. Loads

Is the actual load on the rotor blades at anytime divided by the normal load or gross weight. The load supported by the helicopter in a curved flight path is greater than the total weight of the helicopter. gg. Loads hh. Load Factor ii. Collective Pitch

hh. Load Factor

Located at the left side of the pilot’s seat and is operated by his left hand. Movement changes the pitch angle of the main rotor blades. Raising it increases the blade angle. hh. Load Factor ii. Collective Pitch jj. Throttle Control

ii. Collective Pitch

Mounted on the forward end of the collective pitch lever that control the RPM in the form of a motorcycle twist grip. Therefore, collective pitch control and throttle control are in one assembly. hh. Load Factor ii. Collective Pitch jj. Throttle Control

jj. Throttle Control

Thrust produced by the auxiliary (tail) rotor is governed by the position of the antitorque pedals. Linked to the pitch change mechanism of the tail rotor gear box to permit the pilot to increase or decrease the pitch of the tail rotor blades. ii. Collective Pitch jj. Throttle Control kk. Antitorque (Rudder) Pedals

kk. Antitorque (Rudder) Pedals

Used to change the heading by making a coordinated turn to the desired direction therefore, it controls the attitude and direction of flight. jj. Throttle Control kk. Antitorque (Rudder) Pedals ll. Cyclic Control

ll. Cyclic Control