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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
What is the formula to work out the rate of descent to maintain a 3° glide slope
5 x ground speed (in knots)
26
What gradient is a 3° glide slope
5%
27
What are the altimeter errors
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
28
What is a simple altimeter
No number drum reference to change pressure reference to a pressure datum However can be set to 0 at airfield elevation
29
What is a sensitive altimeter
Can adjust pressure reference Has a ‘vibrator’ to reduce friction (lag) Has a stack of 2 or 3 capsules Multiple pointers
30
What is a servo altimeter
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
31
Advantages of a servo altimeter
Improved accuracy Frictional imperfections are reduced Digital readout / altitude warnings are easily incorporated
32
What happens if there is a blockage in the static line for w altimeter
Freezes
33
What happens if there is a leak inside the pressure hull for a altimeter
Higher pressure from inside the cabin causes altimeter to underread
34
What happens if there is a leak in the altimeter outside the pressure hull
Altimeter will still work but just s but less accurate
35
What if thee is a leak in the altimeter in a unpressurised aircraft
Alt over reads Pressure lower due to cabin suction (caused by airflow past aircraft and static pressure outside dropping (Venturi))
36
In a light single engine what does the white arc mean on the ASI
Vso > Vfe = flap extension speed
37
In a small single engine aircraft what is the green arc
Normal operating speed Up to Vno (max operating never exceed)
38
In a small single engine what does the yellow arc on the asi mean
Caution
39
On a small single engine what does Vne mean
Velocity never exceed
40
On a light twin what does the slow red line on the ASI mean
vmca
41
On a light twin what is the blue line on the ASI
EST rate of climb with one eng out
42
On a light twin what is the fast red line on the ASI
Vne
43
What are the ASI errors
I instrument M manoeuvre P position Compressibility error Density error
44
If the pitot is blocked what happens in level flight
No change
45
If the pitot is blocked on the ASI what happens in the descent
Reduces = blockage makes under read = behaves like altimeter P pitot blocked U under read D descending P pitot blocked O over read C climbing
46
What happens if the static is blocked for the ASI
S static blocked O over reads D descending S static blocked U under read C climbing
47
What happens if there is a leak in the pitot line for the ASI
Will reduces pressure = under read
48
What happens if there is a leak in the static line within the pressure hull for the ASI
High pressure leaks in from cabin = under read
49
What happens to the ASI if there is a static leak outside the pressure hull (unpressurised)
Less static pressure Over read
50
How to convert Celsius to Fahrenheit
Celsius x 1.8 + 32
51
How to convert Fahrenheit to Celsius
Fahrenheit-32 / 1.8
52
what is direct reading temperature
Thermometer
53
What is thermal expansion temperature
Metal expands / contracts Cheap 2 metals = Invar and brass
54
Electrical resistance temperature
Remote sensing Measuring the change in resistance with temperature TURD (temp up resist down) “Wheatstone bridge”
55
What is thermocouple
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
56
What is pyrometry (radiation) temperature sensing
Radiation / ir emitted from heating of a surface
57
What is a TAT probe
Located out of boundary layer and sunlight Collects total air pressure Made of; nickel plated beryllium copper Linear resistance to change in temp
58
What is a TAT sensor
Made of pure platinum wire Resistance sensor High rate of conductivity Rapid response to temp change
59
TAT probe errors
Icing (environmental) = probe body heated Radiate heat (environmental) = sensing equipment hidden internally Frictional heating (design) = probe placed outside boundary layer
60
What is a aspirated TAT probe
Induced flow gives more reliable sensing when stationary
61
What Is SAT
SAT = OAT = reported by net services Undisturbed air Used to calculate TAS and LSS
62
What does TAT =
SAT + ram rise
63
What is ram rise
Adiabatic compression (heating) and is the different between SAT and TAT
64
What is measured ram rise
Ram rise x recovery factor (kr)
65
What is ram air temp (rat) / measured temperature
SAT + ram rise x Kr
66
What is recovery factor
Ability of probe to measure Ram rise depends on the recovery factor (Kr)
67
How does a machmeter work
Measures the ratio of dynamic to static pressure
68
How does a Machmeter deal with compressibility
Cancelled out by design
69
What is the equation for mach number as used by the machmeter
*squareroot* (dynamic pressure/static pressure)
70
What errors does a Machmeter suffer from
IMP instrument Manoeuvre Position
71
Local speed of sound formula
LSS = 38.95 *squareroot* temperature in kelvin
72
What is a MSAI
Mach speed air indicator
73
In a mach meter what happens if the pitot is blocked while descending
Under read
74
In a machmeter what happens if the static is blocked while descending
Over read
75
In a mach meter what happens if there is a pitot leak
Under read
76
In a mach meter what happens if there is a static leak inside the pressure hull
Under read
77
In a mach meter what happens if there is a static leak outside the pressurised hull
Over read
78
What systems require AOA inputs
Stall warning Flight protection Air data computer
79
What are the AOA inputs
Flapper switch AOA vane Probe Null seeking rotor
80
What is the AOA displayed as
Actual AOA Or A proportion of critical angle
81
What is a analogue ADC
Physical inputs Pipes everywhere Very messy Time consuming to diagnose
82
What is a digital ADC
Computer system Processor Peripherals MEMS sensors Always duplicated on large a/c
83
Air data computer (ADC) inputs
``` Static pressure Pitot pressure Measure temperature (RAT) Angle of attack Weight on wheels Configuration ```
84
Air data computer outputs
``` IAS / TAS OAT / TAT Mach number Angle of attack Altitude Vertical speed Vmo/Mmo ```
85
Where is the attractive eminent if s magnet focused
Towards its extremities
86
What is the scope for magnetic variation
0-180
87
What is the vertical component for the earths magnetic field
Z
88
What is the horizontal component for the earths magnetic field
H
89
What is an aclinic line
Angle of dip = 0
90
What is secular magnetic changes
Long term changes in terrestrial magnetism
91
What is predictable magnetic changes
Short term Annual and diurnal based on earths orbit around the sun Diurnal can be associated with heigh of the earths ionosphere
92
What are unpredictable magnetic changes
Short term Related to solar variations
93
What speed does the magnetic poles move at for secular variation
10 miles per year Flip every 450,000 years
94
What are agonic lines
Lines of 0 variation
95
What are isogonal lines
Lines of equal variation
96
What is magnetic deviation
Difference between real magnetic north and where the compass thinks it is
97
What is soft magnetism
Temporary Interference can be stopped by the removal of an object
98
What is hard magnetism
Permanent Electrical components that change the aircrafts field
99
Where is there least compass deviation error
When aligned with magnetic north
100
Compass swing is done when?
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
What is a lubber line
White line on front of compass
102
What does a pendulous suspension do
Allows magnet to easily align itself with the horizontal component of earths magnetic field
103
If I’m northern hemisphere where is the cg of the compass
South
104
What is the compass pivot point made out of
Iridium in tip Jewelled cup
105
How do short magnets help a compass
Keep cg low Less dip
106
How is a aperiodic compass achieved
Filling bowl with damping oil To settle compass quickly after a disturbance
107
Oil used in a compass should:
Remain liquid across full operating temps Not expand or contract excessively with temp change Transparent Non corrosive
108
If you turn right what direction does the liquid swirl
Right
109
When are accelerating errors for a compass greatest
East / west headings Caused by pivot point / cg couple
110
When you accelerate east what direction does the compass rotate
Clockwise Opposite if it’s deceleration
111
What way does the compass rotate when accelerating west
Anti clockwise Opposite for deceleration
112
Equation to find out how much u need to over / undershoot by due to turning errors
(Latitude + bankangle) / 2
113
What is hysteresis
The resistance for an aneroid capsule to move after being in the same position for a long period of time
114
What is gyroscopic rigidity
Any rotating mass tends to resist attempts to change its orientation in space Application of Newton’s 2nd law
115
What affects gyroscopic rigidity
Speed of rotation Density of material Mass
116
How to improve gyroscopic rigidity
Higher density Mass distribution at outer rim High rotational speed
117
What are gimbals
Mounting system / bearings for a gyro
118
What are degrees of freedom
Movements that doesn’t disrupt the gyros axis Gyro spin axis is not a degree of freedom
119
What is gimbal lock
When 2 of the 3 gimbals are in line
120
What happens if a gyro slows down
Drift in horizontal plane Topple in vertical plane
121
What is random / real wander
Can be caused by mechanical imperfections in a gyro Minimised by precision bearings All gyros suffer this
122
What is apparent wander transport wander
Caused by flying from a to b Catered for by caging
123
What is earth rotation wander
Caused by changes in operational latitude Catered for by latitude nut
124
What speed does the earths rotate
Eastwards at 600kts Or 15.04°/ hour At the poles
125
How does he earth rate vary with latitude
Sin of latitude
126
With a vertically aligned gyro where is max and min topple / drift
``` At equator = 0 drift Max topple (90° every 6 hours) ``` At poles = no topple Max drift
127
What is the effects of drift and topple at the poles on a gyro
Vertically aligned gyros appear not to drift or topple Horizontally aligned gyros appear to drift
128
What happens to drift / topple for a gyro at the equator
Vertically aligned gyros appear to topple Horizontally aligned gyros appear not to drift
129
What is random wander
Due to mechanical imperfections
130
How is the attitude indicator gyro positioned
Vertically tied Known as : Earth tied gyro Or Earth gyro Plane of rotation is horizontal
131
How is a directional gyro positioned
Gyro is horizontally tied Plane of rotation is vertical Drift will cause heading errors Max drift @ poles Min drift @ equator
132
What are characteristics in terms of accuracy for a directional gyro
Short term accuracy for heading after being synchronised with magnetic compass
133
What type of erection it a air jet
Coarse erection
134
What type of erection is a wedge plate
Fine erection
135
What is total drift = to
``` Total drift = Earth rate (ER) + transport drift (TD) + random drift (RD) + latitude nut (LN) ```
136
What is the rate of the earth rate
N Pole = -15.04°/hr | S Pole = + 15.04°/hr
137
If a question says local flying or due north then what does transport drift =
0
138
If a question says mechanically perfect then what does random drift =
0
139
What is a remote indicating compass
Combines: Long term accuracy of compass Short term accuracy of gyro 2 gimbals = 2 degrees of freedom Auto cages = adjusts for gyro wander
140
What corrects a remote indicating compass for drift
Gyro drift detected by ‘selsyn’ Messages precision motor which drives gyro back to its correct orientation with magnetic north
141
How far apart are the horns spaced on a flux valve
120°
142
What does a flux valve do
Detects orientation of earths field relative to a/c
143
What is a Hooke’s joint
Allowed pitch and roll without disturbing flux valve Cut out switch to stop signal over 30°
144
What does the flux valve / detector do
Horns gather magnetic field which acts through detector legs Located in wing tips Liquid Excited
145
How quickly does a signal amplifier drive a gyro back to normal
3°/ minute until error = 0
146
What is a free annunciator setting for the RIC
Operates as a directional gyro indicator
147
What is slaved annunciator setting for the RIC
Operated as a Remote indicating compass
148
What are the flux value errors
``` Acceleration Turning Attitude Deviation Variation ```
149
How is the attitude indicator aligned
Vertically tied
150
What is a classic instrument for the attitude indicator
When it’s air driven and rotates anti clockwise when viewed from above
151
What way does an electrically driven attitude indicator rotate
Clockwise when viewed from above
152
What is used to identify angle of roll for an attitude indicator
Sky pointer | Ground pointer
153
What are the limits of the attitude indicator
Pneumatic = roll +/- 110° pitch +/- 60° Electric = roll unlimited pitch +/- 85°
154
How to maintain vertically tied air driven attitude indicator
Coarse alignment = by low cg of the pendulous unit Fine alignment = by the action of the pendulous vanes
155
How to maintain vertically tied electrical attitude indicators
2 mercury level switches 2 torque motors
156
How does the mercury tilt switch work
Mercury moves from side to side in the glass tube covering switches as it’s tilted, making it conductive
157
What are the pendulous errors in the attitude indicator
Acceleration / deceleration (longitudinal) = roll error Turning (lateral) = pitch error Caused by the pendulous unit
158
What are the erection errors for the attitude indicator
Acceleration / deceleration (longitudinal) = pitch errors Turning (lateral) = roll error Caused by pendulous vanes
159
What effect does tilting a gyro slightly forward have on error
Corrects for erection error
160
What effect does tilting a gyro left slightly have on error
Corrects for pendulous error
161
What is a vertical gyro
Orientation is detected electronically = no gyro unit behind the display car Stored in avionics bay
162
What is a turn indicator
Rate gyro Horizontally tied Single gimbal = 1 degree of freedom Responsive to yaw Freedom in pitch / roll
163
What is the rpm for a turn indicator like compared to other gyros And what is it calibrated to
Rpm = less to allow more sensitivity Calibrated to ‘design TAS’ ‘rate 1 turn’
164
In a turn indicator what happens if the rpm is too high
Will over read
165
In a turn indicator what happens if the rpm is too low
Underread
166
In a turn indicator what happens if you pitch up while turning
Over read
167
In a turn indicator what happens if you pitch down while turning
Underread
168
What is the benefit for a turn indicator during unusual attitudes
No topple / unusable condition Provided it is powered
169
How do you make a turn indicator immediately and directly sensitive to roll
Tilted / canted 30°
170
What’s the difference between then indicator and turn coordinators
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
What are the 3 ideal properties of Direct reading compass
Horizontality Sensitivity Aperiodicity
172
Where is flux valve info transmitted
To the error detector
173
Why does a electrically driven artificial horizon have fewer errors compared to a air driven artificial horizon
It has a higher rotor speed and less pendulous

ATPL Instruments (18 decks)

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