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Mod 13 > Rotary Wing Aero Qs > Flashcards

Rotary Wing Aero Qs Flashcards

1
Q

A blade of a helicopter main rotor is

A

Symmetrically cambered

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2
Q

A misaligned blade of a semi rigid rotor will result in

A

Decrease in medium and high frequency vibration

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3
Q

Blade sailing occurs

A

During engine shut down

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4
Q

Translational flight is

A

Achieved by tilting the rotor disc in the required direction of flight

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5
Q

Maximum forward helicopter speed is achieved when

A

Cyclic control is no longer available to overcome disc flapback

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6
Q

The coning angle is a product of

A

Lift and centrifugal force

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7
Q

With an increase in helicopter gross weight the retreating blade stall speed would be

A

Increase

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8
Q

The forces acting on a helicopter in steady forward flight are

A

Thrust is equal to and opposes drag, lift is equal to and opposes weight

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9
Q

A coaxial helicopter utilises

A

Counter rotating shafts on inside the other

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10
Q

On a piston engine helicopter the engagement of centrifugal clutch is indicated by

A

Normal rpm with operating limits

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11
Q

A cyclic pitch change

A

Will cause the rotor disc to tilt in a selected direction

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12
Q

Wash out is used

A

To help reduce the bending moment in the blades

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13
Q

A cyclic friction device allows

A

Control inputs to be set at specific values

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14
Q

A variable incidence horizontal stabiliser

A

Has negative camber and is unaffected by downwash of the helicopter

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15
Q

The tail rotor produces a reaction

A

Opposite to the torque reaction

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16
Q

Ground cushion effect is

A

Extra lift increased by the downwash when the helicopter hovers close to the ground

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17
Q

The Notar system

A

Doesn’t not require a tail rotor

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18
Q

Induced drag in a helicopter occurs

A

At the blade tips

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19
Q

The collective is on which side of the pilot

A

Left

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20
Q

A helicopter has a main rotor which rotates anti-clockwise viewed from above what happens if a loss of anti torque device at cruise speed in flight

A

No appreciable change

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21
Q

A helicopter has a main rotor which rotates anti clockwise viewed form above and is fitted with a tail rotor it will tend to drift sideways to

A

Starboard which ever way the tail rotor is fitted

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22
Q

A helicopter fin helps to give

A

Directional stability about the normal axis

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23
Q

Autorotation

A

Is the product of lift from a freely rotating main rotor

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24
Q

A full articulated main rotor permits the following movements

A

Feathering flapping and dragging

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25
Q

Phase lag is due to the blades

A

Inertia

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26
Q

The mixing unit

A

Ensures that the pilot can use the cyclic input at the same time as collective input

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27
Q

A horizontal stab of a helicopter

A

Prevents excessive nose down attitude in forward flight

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28
Q

A helicopter derives it’s lift

A

And thrust from a power driven main rotor

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29
Q

The amount of lift produced by a rotor depends on the

A

Angle of attack and relative airspeed

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30
Q

Rotor blade pitch angle is the angle between

A

Chord line and hub reference surface

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31
Q

A rigid rotor is on that can

A

Feather only

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32
Q

A helicopter hovering 2m above the ground subject to a strong cross wind will

A

Lose lift due to recirculation

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33
Q

A swash plate and sleeve assy

A

Is titled or moved vertically by flight control inputs

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34
Q

As a helicopter accelerates in forward flight above about 15 knots it will be necessary to

A

Reduce power because of additional lift in translational flight

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35
Q

A helicopter hovering near a tall building will

A

Drift towards it

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36
Q

If the helicopters engine stops during flight the

A

Main rotor will continue to rotate due to the up flow of air

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37
Q

A collective pitch change

A

Is a simultaneous pitch change of all the blades by the same amount

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38
Q

The Actuator position indicator on a helicopter is centred by

A

Operating the Force trim release and moving the cyclic stick

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39
Q

A cyclic pitch change

A

Will cause the rotor disc to tilt in a particular direction

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40
Q

Phase lag is due to

A

Gyroscopic precession

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41
Q

A helicopter is hovering and the pilot applies right pedal. Assuming the main rotor rotates anti clockwise viewed from above the helicopter will

A

Ascend unless the the pilot decrease the rotor rpm

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42
Q

During autorotation what maintains the rotor rpm

A

A reactive thrust force generated by the up flow of air

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43
Q

When the pilot applies left foot forward on the tail rotor control pedals the tail rotor moves

A

To give a net increase on thrust to the right

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44
Q

The direction of the total lift force

A

Always acts from the centre of and at 90 degrees to the rotor disc

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45
Q

Dissymmetry of lift

A

Will tilt the main rotor disc in a particular direction

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46
Q

The airflow over part of the main rotor will be in reverse direction

A

At high forward speed

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47
Q

Pressing the force release trim on a helicopter

A

Relieves the servo load to allow repositioning of the controls on pitch and roll

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48
Q

A helicopter is said to be statically stable if after a disturbance from a stable condition if

A

It’s initial tendency is to return to its original position with or without overshoot

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49
Q

A helicopter is said to have beaut RAL dynamic stability if after an initial disturbance it continues to oscillate at

A

The same rate

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50
Q

A helicopter main rotor blade is twisted from root to tip

A

Equalise lift along the blade

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51
Q

A helicopter main rotor blade pitch change mechanism may be arranged so that when the blade flaps up the pitch reduces in order to

A

Prevent dissymmetry of lift

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52
Q

A helicopter with anti clockwise rotating rotor when moving backwards will have its rotor blade pitch at maximum at

A

90 degrees to the right of longitudinal

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53
Q

A helicopters stabiliser assists in

A

Pitch stability

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54
Q

A shrouded tail rotor

A

Reduces the need for cyclic feathering

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55
Q

A two bladed rotor on a central gimbal is called

A

Semi rigid rotor

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56
Q

After a change in collective pitch the rotor rpm will rise and fall this called

A

Transient droop

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57
Q

After a change in pitch of. Rotor blade the blade will be at maximum flap at

A

90 degree

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58
Q

After a roll to the left of a statically stable helicopter the helicopter would

A

Come back to level flight

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59
Q

After a roll to the left of a statically unstable helicopter the helicopter would

A

Continue to roll further

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60
Q

After over pitching a helicopter centrifugal force

A

Will remain constant at a fixed rotor rpm, the area of the disc decreases and blade coning angle increases

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61
Q

Airflow through the main rotor disc is autorotation is

A

Maybe up or down

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62
Q

An advantage of the symmetrical section blades used in helicopters is that

A

The position of the feather axis and the c of p and c of g coincide providing stability

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63
Q

An elastomeric bearing requires

A

No lubrication

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64
Q

As the aoa of a rotor blade increases it affects the

A

Dragging and the flapping forces

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65
Q

As the rotor head is titled to travel forward what happens to the rearward travelling blades pitch angle

A

Increases

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66
Q

Aspect ratio is the ratio of the

A

Blade span to the chord

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67
Q

Assuming the phase lag of a rotor blade is 90 degrees and the control advance angle is 15 degrees then the pitch operating arm must be at the highest point of the swash plate

A

75 degrees ahead of the highest flapping point

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68
Q

At a given power setting ground cushion effect is most effective when a helicopter is hovering over

A

A hard level surface

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69
Q

Autorotation

A

Is the product of lift from freely rotating rotor blades

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70
Q

Authoritative force attempts to pull the rotor blade

A

In the direction of normal rotation

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71
Q

Autorotative force is the

A

Component of the total reaction which acts forward in the plane of rotation in opposition to drag

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72
Q

Certain helicopters tend to tilt laterally when landing this problem can be overcome by placing the tail rotor thrust

A

I’m line with the main rotor hub

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73
Q

Changes in aircraft weight

A

Cause corresponding changes in total drag due to the associated lift change

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74
Q

Climbs with forward speed require less power than vertical climbers because of

A

Translational lift

75
Q

Disc loading is defined as the

A

Ratio of gross weight to disc area

76
Q

Dropping off helicopter blades is compensated by

A

Centrifugal force

77
Q

During an autorotation decent rotor rpm will be

A

Higher than in powered flight

78
Q

During autorotation the rudder pedals

A

Would need to be backed off due to the loss of torque

79
Q

During decent with power on on a helicopter

A

Lift drag thrust and weight are acting on the helo

80
Q

During forward flight the advancing blade will

A

Flap up

81
Q

During forward flight the retreating blade will

A

Flap down

82
Q

During the flare in autorotation the rotor rpm will

A

Increase

83
Q

For a helicopter in autorotation what forward speed will achieve the maximum glide distance

A

Greater than minimum glide speed

84
Q

Forward velocity causes the advancing blade to

A

Flap up and reduce lift

85
Q

Ground cushion effect is due to

A

Increased pressure under the rotors

86
Q

Ground cushion effect is produced by

A

Increased pressure under the main rotor disc

87
Q

Ground effect is only apparent

A

I’m low speed translational flight up to one times the disc diameter from the ground

88
Q

Ground effect will be most apparent when

A

Hovering close to the ground

89
Q

Helicopter blades are usually

A

Symmetrical

90
Q

Helicopter derives it’s lift from

A

The blade of the helicopter creates a low pressure above it

91
Q

Helicopter experiences VOR text ring state

A

It experiences turbulence and descends

92
Q

Helicopters in forward flight are usually

A

Directionally stable

93
Q

How do you measure HUMS gearbox vibration

A

Accelerometers

94
Q

How many rotor blades are on a helicopter

A

Depends on helicopter design

95
Q

If a helicopter rotor disc is rotating anti-clockwise viewed from above where would a pitch input be fed into the disc to move the helicopter rearward

A

Right of the longitudinal axis

96
Q

If a helicopters main rotor blades are over pitched

A

Rotor rpm will decrease

97
Q

If the aoa is increased on a main rotor blade

A

There is in an increase in drag

98
Q

If the blade aoa increases

A

Lift and drag increases

99
Q

If the main rotor of a helicopter rotates in anti-clockwise direction when viewed from above and a hovering left turn is required the following movements of the controls are selected

A

Rudder pedal to the left and increase throttle

100
Q

I’m a NOTAR system air is ducted down the tail boom to produce a predetermined amount of lift

A

Over one side of the boom to counteract changing torque from the main rotor

101
Q

In forward flight the relative air velocity at each blade

A

Is greatest for the advancing blade

102
Q

I’m forward flight if a helicopter had no flapping hinges it would tend to

A

Roll towards the side of the retreating blade

103
Q

In forward flight the advancing blade would be expected to

A

Flap up

104
Q

Instead of the flapping hinge being mounted at right angles to the spans of the blade the delta three hinge is set at an angle

A

Such that when a blade flaps up the pitch angle of the blade is reduced

105
Q

Lift generated by a blade is proportional to the

A

Relative airflow and the aoa

106
Q

Lift in a helicopter is a result of

A

Aoa x velocity squared

107
Q

Lift is generated by

A

Low pressure above the blade

108
Q

Movement of the collective control will

A

Increase the pitch of the main rotor blades

109
Q

On a helicopter rotor disc lift happens

A

Immediately

110
Q

On a helicopter the rotor disc is

A

The swept area between the blade tips

111
Q

On a helicopter what is blade dragging

A

Movement of each blade horizontally about the vertical hinge

112
Q

On a helicopter what is a vortex ring state

A

tip vortex build up during hover

113
Q

Over pitch causes

A

Blades to cone up

114
Q

Over pitching of a helicopter collective control may lead to

A

Excessive blade coning and an attendant loss of rotor useful force

115
Q

Relative airflow over a helicopter blade

A

Increases at the tip

116
Q

Relative velocity of a helicopter rotor

A

Increases at forward travelling blade

117
Q

Rotor blade sailing is a problem at

A

Low rotor rpm at engine shut down

118
Q

Rotor tip vortices are strongest when

A

Hovering with high weight

119
Q

Solidity of the rotor is the ratio of

A

Blade area to disc area

120
Q

Stability of a helicopter is its

A

Ability to return to original attitude after displacement

121
Q

Switches on the collective of turbine powered helicopters

A

Searchlight controls force trim release switch landing light and collective trim where four axis autopilot is fitted

122
Q

Tail rotor effects the helicopter in

A

Horizontal axis

123
Q

The advancing blade of a helicopter is the on moving

A

One moving forward into the relative airflow

124
Q

The aerofoils shape of a main rotor blade is symmetrical in order to make the blade have

A

A relatively stable c of p position with changes in aoa

125
Q

The aoa of a blade is the.

A

Angle between the chord line and relative airflow

126
Q

The bell stability argumentation system is based on

A

Gyroscopic forces

127
Q

The best design of a rotor blade is where the c of p

A

Does not move

128
Q

The blade stalling speed will

A

Increase with a increase in weight

129
Q

The c of p of an aerofoils is that point on the chord line

A

At which the lift forces resultant is said to act

130
Q

The choice of aerofoils section for a rotor blade is such that

A

It has a stable c of p

131
Q

The cyclic stick controls a helicopter in

A

Pitch and roll

132
Q

The difference between transient droop and static droop is

A

Undrswing

133
Q

The distribution of lift is equalised along the length of a helicopter rotor blade by

A

Incorporating a twist or change of section towards the tip of the blade

134
Q

The forces which govern the coning angle are

A

Lift and centrifugal force

135
Q

The main rotor assy of a helicopter provides

A

Lift a component of which is horizontal so thrust is obtained

136
Q

The main rotor drive shaft is titled laterally on some helicopters to correct tail rotor

A

Drift

137
Q

The maximum forward speed of a helicopter is limited by

A

Retreating blade stall and forward speed of advancing blade

138
Q

The pilot of a helicopter can overcome vortex ring effect by

A

Lowering the collective pitch lever and easing the cyclic forward

139
Q

The pilot of a helicopter that is in a vortex ring state will encounter turbulence and will experience

A

Vibration a high rate of decent and some partial loss of control

140
Q

The purpose of an offset vertical stab is to

A

Relieve some of the load on the tail rotor during forward flight

141
Q

The purpose of the horizontal stab is to

A

Maintain the aircraft in as near a horizontal attitude as possible during forward flight

142
Q

The rotor blades operated at the best lift drag ratio when their

A

Aoa is about +3 degrees

143
Q

The rotor cone is formed by

A

Centrifugal force and lift

144
Q

The rotor disc is

A

The distance between tip to tip

145
Q

The rpm of the rotor blades is constant within small limits to

A

Prevent blades folding up during flight

146
Q

The stalling speed of a helicopter blade

A

Is increased when the helicopter is heavier

147
Q

The tail rotor

A

Produces a force opposing torque reaction

148
Q

The vortex ring state which may develop under conditions of a power on decent at low forward airspeed is

A

An unstable condition which may result in an uncontrolled rate of decent

149
Q

To maintain the position of the helicopter with a decrease in air density the pilot must increase

A

Collective pitch

150
Q

Tracking is carried out to

A

Align the main rotor blade tip path

151
Q

Translational drift is

A

The tendency for the aircraft to drift laterally

152
Q

Translational flight is

A

Achieved by tilting the rotor disc in the direction of flight

153
Q

Upwash on a helicopter would result in

A

Increase in lift without an increase in power

154
Q

Vortex ring state requires

A

Power on decent

155
Q

What damps vibrations on a helicopter

A

Bifilar damper

156
Q

What design factor govern rpm of helicopter rotor

A

Weight of the blade

157
Q

What effect does the ground have on a helicopter

A

Increases lift

158
Q

What forces are acting ok the helicopter during decent

A

Lift and weight

159
Q

What happens to a helicopter in autorotative flight

A

The rotor goes in the normal direction of rotation

160
Q

What is the advancing blade on a helicopter doing

A

Going to the lowest point

161
Q

What is the swash plate on a helicopter used for

A

Control of the pitch of the rotor blades

162
Q

What principle does the delta 3 hinge use

A

Offset hinges

163
Q

When a blade is flapping up

A

Pitch will decrease

164
Q

When a blade moves about the flapping hinge

A

The drag forces on the blade change and the aoa changes

165
Q

When a helicopter rotor disc is tilted forward what happens to the pitch of the retreating blade

A

Increases

166
Q

When air flow velocity over an upper cambered surface of an aerofoils decreases what takes places

A

Pressure increases
Lift decreases

167
Q

When an aerofoils stalls

A

Lift decreases and drag increases

168
Q

When entering into a stable autorotative state the main rotor rpm will initially

A

Decrease

169
Q

When moving from the hover to forward flight it is necessary to

A

Increase the engine power

170
Q

When oat increases what happens to a helicopter operating ceiling

A

Decrease

171
Q

When the cyclic stick is eased forward in the hover position

A

Vertical lift is reduced

172
Q

When the helicopter moves from the hover to translational flight the lift vector will

A

Remain vertical

173
Q

When the rotor blade increases it’s aoa the c of p

A

Does not move

174
Q

When the rotor blade is flapping down

A

the pitch angle is less than the aoa

175
Q

When the rotor blade is flapping up the aoa is

A

Is less than the pitch angle

176
Q

When will the needle spilt in a joint rotor / engine rpm instrument

A

On clutch slip

177
Q

Which direction is the air flowing through the main rotor during autorotation

A

Upwards

178
Q

Which part of the rotor disc produces the most lift during forward flight

A

The front portion

179
Q

With a drop in ambient temperature aJ aircraft service ceiling will

A

Not be affected

180
Q

With a fixed collective pitch as an autorotating helicopter loses its forward velocity the rotor rpm will

A

Decrease

181
Q

With an increase in forward velocity of a helicopter the increase in parasitic drag will cause the fuselage to

A

Pitch down with a I crease in forward speed

182
Q

With an increase in its aoa the drag acting on a rotor blade

A

Increases

183
Q

With the tail rotor pedals in neutral the tail rotor blade pitch will be

A

Positive

Mod 13 (22 decks)

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