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ATPL Instruments > Basic Instruments > Flashcards

Basic Instruments Flashcards

1
Q

What is analogue

A

Qualitative

Easy to see rate of change

Comparative

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2
Q

What is digital

A

Quantitive

Precise value

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3
Q

What is LRV

A

Line replaceable unit

In avionics bay

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4
Q

Is pressure sensing linear or non linear

A

Non linear

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5
Q

What does 1 pascal =

A

1 newton / m^2

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6
Q

1013.25 in different units?

A
  1. 97 PSI (rounded to 15)

29. 92 inHg (rounded to 30)

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7
Q

What is measured in psi

A

Engine oil
Hydraulic system pressures
Cabin differential pressure

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8
Q

What does MEMS technology sense (micro - electromechanical systems)

A

Engine oil pressure
Hydraulic system pressures
Cabin differential pressures

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9
Q

What is a aneroid capsule

A

Hollow
Single / multi layered
Supported by spring
Sealed / partially vacuumed

Senses low pressure

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10
Q

What is a pressure capsule

A

Like a aneroid capsule except not sealed

Senses low pressure

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11
Q

What is a diaphragms

A

Takes into account pitot + static

Just has dynamic pressure

Senses low pressure

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12
Q

What does a bourdon tube sense

A

High pressure

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13
Q

What instruments measure static pressure only

A

Altimeter

Vertical speed indicator

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14
Q

What are the 3 main instrument errors

A

I instrument = mechanical imperfections

M = manoeuvring

P = position

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15
Q

What are the other names for a vertical speed indicator

A

Vario
Variometer
Ratiometer
Rate of climb and descent indicator (RCDI)

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16
Q

What capsule is in a vertical speed indicator

A

Pressure capsule

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17
Q

What is a metering unit made up of

A 
Capillary (laminar) 
Knife edge (turbulent)
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18
Q

Errors associated with a vertical speed indicator

A

I instrument
M manoeuvre
P position

Time lag

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19
Q

What does makes an instantaneous vertical speed indicator (IVSI)

A

It has a accelerometer unit / metering unit / dashpot

To reduce time lag

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20
Q

How does a dashpot / accelerometer unit / metering unit work?

A

In descent accelerometer moves up increasing pressure in capsule

Reverse for climb

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21
Q

What are the errors for a accelerometer unit / dashpot / metering unit

A

In turbulence dashpot moves = fluctuations in VSI

Turning = g forces = indication of climb

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22
Q

What happens if there is a leak in a vertical speed indicator outside of the pressure hull

A

Slight deviation from actual vertical speed

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23
Q

What happens if there is a blockage in the vertical speed indicator

A

Frozen instrument

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24
Q

What happens if there is a leak in a vertical speed indicator inside the pressure hull

A

If cabin altitude reduces then VSI will show a descent

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25
Q

What is the formula to work out the rate of descent to maintain a 3° glide slope

A

5 x ground speed (in knots)

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26
Q

What gradient is a 3° glide slope

A

5%

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27
Q

What are the altimeter errors

A

I instrument
M manoeuvre
P position

Temperature (if there is a isa deviation)

Height error = 4 x indicated alt in 1000’s or feet x ISA deviation

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28
Q

What is a simple altimeter

A

No number drum reference to change pressure reference to a pressure datum

However can be set to 0 at airfield elevation

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29
Q

What is a sensitive altimeter

A

Can adjust pressure reference

Has a ‘vibrator’ to reduce friction (lag)

Has a stack of 2 or 3 capsules

Multiple pointers

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30
Q

What is a servo altimeter

A

Has less lag

When ‘E’ and ‘I’ bar are parallel = no output

When un parallel = voltage in certain part of ‘E’ bar = output into secondary circuit

Eventually E bar resets to parallel to I bar

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31
Q

Advantages of a servo altimeter

A

Improved accuracy

Frictional imperfections are reduced

Digital readout / altitude warnings are easily incorporated

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32
Q

What happens if there is a blockage in the static line for w altimeter

A

Freezes

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33
Q

What happens if there is a leak inside the pressure hull for a altimeter

A

Higher pressure from inside the cabin causes altimeter to underread

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34
Q

What happens if there is a leak in the altimeter outside the pressure hull

A

Altimeter will still work but just s but less accurate

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35
Q

What if thee is a leak in the altimeter in a unpressurised aircraft

A

Alt over reads

Pressure lower due to cabin suction (caused by airflow past aircraft and static pressure outside dropping (Venturi))

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36
Q

In a light single engine what does the white arc mean on the ASI

A

Vso > Vfe = flap extension speed

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37
Q

In a small single engine aircraft what is the green arc

A

Normal operating speed

Up to Vno (max operating never exceed)

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38
Q

In a small single engine what does the yellow arc on the asi mean

A

Caution

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39
Q

On a small single engine what does Vne mean

A

Velocity never exceed

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40
Q

On a light twin what does the slow red line on the ASI mean

A

vmca

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41
Q

On a light twin what is the blue line on the ASI

A

EST rate of climb with one eng out

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42
Q

On a light twin what is the fast red line on the ASI

A

Vne

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43
Q

What are the ASI errors

A

I instrument
M manoeuvre
P position

Compressibility error

Density error

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44
Q

If the pitot is blocked what happens in level flight

A

No change

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45
Q

If the pitot is blocked on the ASI what happens in the descent

A

Reduces = blockage makes under read = behaves like altimeter

P pitot blocked
U under read
D descending

P pitot blocked
O over read
C climbing

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46
Q

What happens if the static is blocked for the ASI

A

S static blocked
O over reads
D descending

S static blocked
U under read
C climbing

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47
Q

What happens if there is a leak in the pitot line for the ASI

A

Will reduces pressure = under read

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48
Q

What happens if there is a leak in the static line within the pressure hull for the ASI

A

High pressure leaks in from cabin = under read

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49
Q

What happens to the ASI if there is a static leak outside the pressure hull (unpressurised)

A

Less static pressure

Over read

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50
Q

How to convert Celsius to Fahrenheit

A

Celsius x 1.8 + 32

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51
Q

How to convert Fahrenheit to Celsius

A

Fahrenheit-32 / 1.8

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52
Q

what is direct reading temperature

A

Thermometer

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53
Q

What is thermal expansion temperature

A

Metal expands / contracts

Cheap

2 metals = Invar and brass

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54
Q

Electrical resistance temperature

A

Remote sensing

Measuring the change in resistance with temperature

TURD (temp up resist down)

“Wheatstone bridge”

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55
Q

What is thermocouple

A

Remote sensing

Hot junction at place where heat is

Heating creates slight voltage

Does not require voltage input for signal

Modern engine connected in parallel

Materials = chromel and alumel

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56
Q

What is pyrometry (radiation) temperature sensing

A

Radiation / ir emitted from heating of a surface

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57
Q

What is a TAT probe

A

Located out of boundary layer and sunlight

Collects total air pressure

Made of; nickel plated beryllium copper

Linear resistance to change in temp

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58
Q

What is a TAT sensor

A

Made of pure platinum wire

Resistance sensor

High rate of conductivity

Rapid response to temp change

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59
Q

TAT probe errors

A

Icing (environmental) = probe body heated

Radiate heat (environmental) = sensing equipment hidden internally

Frictional heating (design) = probe placed outside boundary layer

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60
Q

What is a aspirated TAT probe

A

Induced flow gives more reliable sensing when stationary

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61
Q

What Is SAT

A

SAT = OAT = reported by net services

Undisturbed air

Used to calculate TAS and LSS

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62
Q

What does TAT =

A

SAT + ram rise

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63
Q

What is ram rise

A

Adiabatic compression (heating) and is the different between SAT and TAT

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64
Q

What is measured ram rise

A

Ram rise x recovery factor (kr)

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65
Q

What is ram air temp (rat) / measured temperature

A

SAT + ram rise x Kr

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66
Q

What is recovery factor

A

Ability of probe to measure Ram rise depends on the recovery factor (Kr)

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67
Q

How does a machmeter work

A

Measures the ratio of dynamic to static pressure

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68
Q

How does a Machmeter deal with compressibility

A

Cancelled out by design

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69
Q

What is the equation for mach number as used by the machmeter

A

squareroot (dynamic pressure/static pressure)

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70
Q

What errors does a Machmeter suffer from

A

IMP

instrument
Manoeuvre
Position

71
Q

Local speed of sound formula

A

LSS = 38.95 squareroot temperature in kelvin

72
Q

What is a MSAI

A

Mach speed air indicator

73
Q

In a mach meter what happens if the pitot is blocked while descending

A

Under read

74
Q

In a machmeter what happens if the static is blocked while descending

A

Over read

75
Q

In a mach meter what happens if there is a pitot leak

A

Under read

76
Q

In a mach meter what happens if there is a static leak inside the pressure hull

A

Under read

77
Q

In a mach meter what happens if there is a static leak outside the pressurised hull

A

Over read

78
Q

What systems require AOA inputs

A

Stall warning
Flight protection
Air data computer

79
Q

What are the AOA inputs

A

Flapper switch
AOA vane

Probe
Null seeking rotor

80
Q

What is the AOA displayed as

A

Actual AOA

Or

A proportion of critical angle

81
Q

What is a analogue ADC

A

Physical inputs
Pipes everywhere
Very messy
Time consuming to diagnose

82
Q

What is a digital ADC

A

Computer system
Processor
Peripherals
MEMS sensors

Always duplicated on large a/c

83
Q

Air data computer (ADC) inputs

A 
Static pressure 
Pitot pressure 
Measure temperature (RAT)
Angle of attack
Weight on wheels 
Configuration
84
Q

Air data computer outputs

A 
IAS / TAS 
OAT / TAT
Mach number 
Angle of attack
Altitude 
Vertical speed 
Vmo/Mmo
85
Q

Where is the attractive eminent if s magnet focused

A

Towards its extremities

86
Q

What is the scope for magnetic variation

A

0-180

87
Q

What is the vertical component for the earths magnetic field

A

Z

88
Q

What is the horizontal component for the earths magnetic field

A

H

89
Q

What is an aclinic line

A

Angle of dip = 0

90
Q

What is secular magnetic changes

A

Long term changes in terrestrial magnetism

91
Q

What is predictable magnetic changes

A

Short term

Annual and diurnal based on earths orbit around the sun

Diurnal can be associated with heigh of the earths ionosphere

92
Q

What are unpredictable magnetic changes

A

Short term

Related to solar variations

93
Q

What speed does the magnetic poles move at for secular variation

A

10 miles per year

Flip every 450,000 years

94
Q

What are agonic lines

A

Lines of 0 variation

95
Q

What are isogonal lines

A

Lines of equal variation

96
Q

What is magnetic deviation

A

Difference between real magnetic north and where the compass thinks it is

97
Q

What is soft magnetism

A

Temporary

Interference can be stopped by the removal of an object

98
Q

What is hard magnetism

A

Permanent

Electrical components that change the aircrafts field

99
Q

Where is there least compass deviation error

A

When aligned with magnetic north

100
Q

Compass swing is done when?

A

Changes in operating base involving s large change in dip

Major changes in aircraft equipment

When a/c parked in same direction for long period

When new compass is fitted

Excessive compass deviation suspected

Specified in maintenance schedule

101
Q

What is a lubber line

A

White line on front of compass

102
Q

What does a pendulous suspension do

A

Allows magnet to easily align itself with the horizontal component of earths magnetic field

103
Q

If I’m northern hemisphere where is the cg of the compass

A

South

104
Q

What is the compass pivot point made out of

A

Iridium in tip

Jewelled cup

105
Q

How do short magnets help a compass

A

Keep cg low

Less dip

106
Q

How is a aperiodic compass achieved

A

Filling bowl with damping oil

To settle compass quickly after a disturbance

107
Q

Oil used in a compass should:

A

Remain liquid across full operating temps

Not expand or contract excessively with temp change

Transparent

Non corrosive

108
Q

If you turn right what direction does the liquid swirl

A

Right

109
Q

When are accelerating errors for a compass greatest

A

East / west headings

Caused by pivot point / cg couple

110
Q

When you accelerate east what direction does the compass rotate

A

Clockwise

Opposite if it’s deceleration

111
Q

What way does the compass rotate when accelerating west

A

Anti clockwise

Opposite for deceleration

112
Q

Equation to find out how much u need to over / undershoot by due to turning errors

A

(Latitude + bankangle) / 2

113
Q

What is hysteresis

A

The resistance for an aneroid capsule to move after being in the same position for a long period of time

114
Q

What is gyroscopic rigidity

A

Any rotating mass tends to resist attempts to change its orientation in space

Application of Newton’s 2nd law

115
Q

What affects gyroscopic rigidity

A

Speed of rotation

Density of material

Mass

116
Q

How to improve gyroscopic rigidity

A

Higher density

Mass distribution at outer rim

High rotational speed

117
Q

What are gimbals

A

Mounting system / bearings for a gyro

118
Q

What are degrees of freedom

A

Movements that doesn’t disrupt the gyros axis

Gyro spin axis is not a degree of freedom

119
Q

What is gimbal lock

A

When 2 of the 3 gimbals are in line

120
Q

What happens if a gyro slows down

A

Drift in horizontal plane

Topple in vertical plane

121
Q

What is random / real wander

A

Can be caused by mechanical imperfections in a gyro

Minimised by precision bearings

All gyros suffer this

122
Q

What is apparent wander transport wander

A

Caused by flying from a to b

Catered for by caging

123
Q

What is earth rotation wander

A

Caused by changes in operational latitude

Catered for by latitude nut

124
Q

What speed does the earths rotate

A

Eastwards at

600kts

Or

15.04°/ hour

At the poles

125
Q

How does he earth rate vary with latitude

A

Sin of latitude

126
Q

With a vertically aligned gyro where is max and min topple / drift

A 
At equator = 0 drift 
Max topple (90° every 6 hours)

At poles = no topple
Max drift

127
Q

What is the effects of drift and topple at the poles on a gyro

A

Vertically aligned gyros appear not to drift or topple

Horizontally aligned gyros appear to drift

128
Q

What happens to drift / topple for a gyro at the equator

A

Vertically aligned gyros appear to topple

Horizontally aligned gyros appear not to drift

129
Q

What is random wander

A

Due to mechanical imperfections

130
Q

How is the attitude indicator gyro positioned

A

Vertically tied

Known as :
Earth tied gyro
Or
Earth gyro

Plane of rotation is horizontal

131
Q

How is a directional gyro positioned

A

Gyro is horizontally tied

Plane of rotation is vertical

Drift will cause heading errors
Max drift @ poles
Min drift @ equator

132
Q

What are characteristics in terms of accuracy for a directional gyro

A

Short term accuracy for heading after being synchronised with magnetic compass

133
Q

What type of erection it a air jet

A

Coarse erection

134
Q

What type of erection is a wedge plate

A

Fine erection

135
Q

What is total drift = to

A 
Total drift = 
Earth rate (ER) 
\+ transport drift (TD) 
\+ random drift (RD)
\+ latitude nut (LN)
136
Q

What is the rate of the earth rate

A

N Pole = -15.04°/hr

S Pole = + 15.04°/hr

137
Q

If a question says local flying or due north then what does transport drift =

A

0

138
Q

If a question says mechanically perfect then what does random drift =

A

0

139
Q

What is a remote indicating compass

A

Combines:
Long term accuracy of compass

Short term accuracy of gyro

2 gimbals = 2 degrees of freedom

Auto cages = adjusts for gyro wander

140
Q

What corrects a remote indicating compass for drift

A

Gyro drift detected by ‘selsyn’

Messages precision motor which drives gyro back to its correct orientation with magnetic north

141
Q

How far apart are the horns spaced on a flux valve

A

120°

142
Q

What does a flux valve do

A

Detects orientation of earths field relative to a/c

143
Q

What is a Hooke’s joint

A

Allowed pitch and roll without disturbing flux valve

Cut out switch to stop signal over 30°

144
Q

What does the flux valve / detector do

A

Horns gather magnetic field which acts through detector legs

Located in wing tips

Liquid

Excited

145
Q

How quickly does a signal amplifier drive a gyro back to normal

A

3°/ minute until error = 0

146
Q

What is a free annunciator setting for the RIC

A

Operates as a directional gyro indicator

147
Q

What is slaved annunciator setting for the RIC

A

Operated as a Remote indicating compass

148
Q

What are the flux value errors

A 
Acceleration 
Turning 
Attitude 
Deviation 
Variation
149
Q

How is the attitude indicator aligned

A

Vertically tied

150
Q

What is a classic instrument for the attitude indicator

A

When it’s air driven and rotates anti clockwise when viewed from above

151
Q

What way does an electrically driven attitude indicator rotate

A

Clockwise when viewed from above

152
Q

What is used to identify angle of roll for an attitude indicator

A

Sky pointer

Ground pointer

153
Q

What are the limits of the attitude indicator

A

Pneumatic = roll +/- 110° pitch +/- 60°

Electric = roll unlimited pitch +/- 85°

154
Q

How to maintain vertically tied air driven attitude indicator

A

Coarse alignment = by low cg of the pendulous unit

Fine alignment = by the action of the pendulous vanes

155
Q

How to maintain vertically tied electrical attitude indicators

A

2 mercury level switches

2 torque motors

156
Q

How does the mercury tilt switch work

A

Mercury moves from side to side in the glass tube covering switches as it’s tilted, making it conductive

157
Q

What are the pendulous errors in the attitude indicator

A

Acceleration / deceleration (longitudinal) = roll error

Turning (lateral) = pitch error

Caused by the pendulous unit

158
Q

What are the erection errors for the attitude indicator

A

Acceleration / deceleration (longitudinal) = pitch errors

Turning (lateral) = roll error

Caused by pendulous vanes

159
Q

What effect does tilting a gyro slightly forward have on error

A

Corrects for erection error

160
Q

What effect does tilting a gyro left slightly have on error

A

Corrects for pendulous error

161
Q

What is a vertical gyro

A

Orientation is detected electronically

= no gyro unit behind the display car

Stored in avionics bay

162
Q

What is a turn indicator

A

Rate gyro

Horizontally tied

Single gimbal = 1 degree of freedom

Responsive to yaw

Freedom in pitch / roll

163
Q

What is the rpm for a turn indicator like compared to other gyros

And what is it calibrated to

A

Rpm = less to allow more sensitivity

Calibrated to ‘design TAS’ ‘rate 1 turn’

164
Q

In a turn indicator what happens if the rpm is too high

A

Will over read

165
Q

In a turn indicator what happens if the rpm is too low

A

Underread

166
Q

In a turn indicator what happens if you pitch up while turning

A

Over read

167
Q

In a turn indicator what happens if you pitch down while turning

A

Underread

168
Q

What is the benefit for a turn indicator during unusual attitudes

A

No topple / unusable condition

Provided it is powered

169
Q

How do you make a turn indicator immediately and directly sensitive to roll

A

Tilted / canted 30°

170
Q

What’s the difference between then indicator and turn coordinators

A

Turn indicator =

  • not sensitive to roll
  • always correctly indicates yaw and thus direction of spin

Turn coordinator=

  • is sensitive to roll
  • if in inverted spin may indicate incorrectly
171
Q

What are the 3 ideal properties of Direct reading compass

A

Horizontality

Sensitivity

Aperiodicity

172
Q

Where is flux valve info transmitted

A

To the error detector

173
Q

Why does a electrically driven artificial horizon have fewer errors compared to a air driven artificial horizon

A

It has a higher rotor speed and less pendulous

ATPL Instruments (18 decks)

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