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Basic Digital Techniques and Electronic Instrument Systems > At a glance > Flashcards

At a glance Flashcards

1
Q

what is the typical configuration of a cockpit EIS system?

A
  • 6 screens DU’s , driven by 2 DEU’s

- DEU 1 supplies DU’s 1 - 3

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2
Q

what do the DU’s in a typical cockpit EIS system display?

A
  • 2 PFD, attitude, speed, altitude
  • 2 ND, map, radar, route planning
  • 2 Engine Instruments
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3
Q

in event of loss of power to DU’s or failure, how will the DU’s reorder to display essential information?

A
  • PFD will be displayed at highest priority

- Engine Instruments will be displayed at second highest priority

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4
Q

how would the loss of a DEU be displayed?

A

Red X displayed across whole of associated DU’s

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5
Q

what does a red X on part of DU indicate?

A

immediate flight crew action to restore data

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6
Q

what does an amber X on part of DU indicate?

A

action required but flight crew can choose to delay action

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7
Q

what base is decimal?

A

10

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8
Q

what base is binary?

A

2

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9
Q

what base is octal?

A

8

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10
Q

what base is hexadecimal?

A

16

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11
Q

binary is split into groups of ____ to convert to octal

A

3

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12
Q

binary is split into groups of ____ to convert to hexadecimal

A

4

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13
Q

what do DAC and ADC mean with regards to data conversion?

A
  • DAC - Digital to Analogue Converter

- ADC - Analogue to Digital Converter

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14
Q

how many inputs would a 4-bit DAC have?

A

4

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15
Q

what is the quantisation interval in a DAC?

A
  • maximum output voltage/maximum binary input

- equivalent to the LSB

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16
Q

what is the quantisation level in a DAC?

A
  • quantisation interval (LSB) x binary input
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17
Q

what is accuracy with regards to data conversion?

A
  • variance in output voltage from predicted voltage

- given in %

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18
Q

what is resolution with regards to data conversion?

A
  • the smallest increment of voltage that can be obtained from a converter
  • dependent on amount of input bits to converter
  • more input bits, the higher the resolution for a given voltage
  • (quantisation interval/maximum output) x 100
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19
Q

what are the characteristics of a weighted resistor DAC?

A
  • resistors half in size from the LSB upwards

- MSB smallest resistor

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20
Q

what is the main disadvantage of a wighted resistor DAC?

A
  • need a lot of different value resistors = expensive
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21
Q

what are the characteristics of a R2-R resistor DAC?

A
  • resistor branch (2 resistors) for each binary unit
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22
Q

what is the main advantage of a R2-R resistor DAC?

A
  • only need 2 values of resistor = cheap
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23
Q

what is sampling rate with regards to data conversions?

A
  • higher sampling rate = smaller quantisation level = good reproduction
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24
Q

how does a successive approximation DAC work?

A
  • tests input voltage at half maximum, then half again etc
  • fixed time conversion, time = counts
  • 4 bit has 4 counts, 8 bit has 8 counts etc
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25
Q

how does a fast parallel ADC work?

A
  • uses comparators, analogue is converted in one action
  • number of comparators required = 1 for each data count except for zero
  • formulae 2n - 1 where n = number of bits
  • system is fast but expensive
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26
Q

what does a data bus do?

A

transfers data from point a to point b using digital signals

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27
Q

what types of data transmission are there?

A
  • simplex
  • half duplex
  • full duplex
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28
Q

how does simplex data transmission work?

A

only goes in one direction

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29
Q

how does half duplex data transmission work?

A

goes in both direction but only one direction at a time

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30
Q

how does full duplex data transmission work?

A

goes in both directions simultaneously

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31
Q

why types of aircraft data bus are there?

A
  • ARINC 429

- ARINC 629

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32
Q

what are the characteristics for ARINC 429?

A
  • cable = twisted pair with shield
  • logic 1 = +10V, logic 0 = -10V, null = 0V
  • 1 null = space space between bits for internal clocking
  • 4 nulls = between data word to allow word synchronisation
  • two speeds, slow = 12-14k bits, fast = 100k bits
  • words are 32 bits long using odd parity
  • label = 1st 8 bits
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33
Q

what are the characteristics of ARINC 629?

A
  • cable = twisted pair without shield
  • high speed - 2 Mb per second
  • up to 100m long
  • can have 120 terminals
  • terminated with data us terminator
  • inductive couplers
  • stub cables up to 40m long
  • 1 message has up to 31 word strings, each word string has up to 256 data words, each data word has 20 bits
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34
Q

what types of gates are there?

A
  • AND
  • OR
  • NOT
  • NAND
  • NOR
  • EXOR
  • EXNOR
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35
Q

how do you calculate the number of outputs in a logic gate?

A

2n where n in the number of inputs

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36
Q

the general purpose computer has 4 main sections, what are they?

A
  • CPU, memory types, databuses and input/output devices
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37
Q

what does the CPU (central processing unit) contain?

A
  • ALU (arithmetic and logic unit)
  • bus interface
  • timing and control unit
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38
Q

what is the purpose if the ALU within the CPU

A

to carry out arithmetic and logic

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39
Q

what is the purpose of the bus interface unit within the CPU?

A

moves information and commands through the data buses in the computer

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40
Q

what is the purpose of the timing and control unit within the CPU?

A

maintains timing and control of the systems to stop information from crashing

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41
Q

what three data buses are there within a basic computer?

A
  • address bus
  • data bus
  • timing and control
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42
Q

what is the function of the address bus within a computer?

A
  • ONE WAY data flow from CPU to ROM, RAM, I/O
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43
Q

what is the function of the data bus within a computer?

A
  • TWO WAY data flow from/to CPU to ROM, RAM, I/O
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44
Q

what is the function of the timing and control bus within a computer?

A
  • ONE WAY signal flow from CPU to ROM, RAM, I/O
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45
Q

what 5 types of memory are available in a computer?

A
  • ROM
  • PROM
  • RAM
  • EPROM
  • EEPROM
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46
Q

what are the characteristics of ROM memory?

A
  • non volatile

- programmed at manufacture, not re-programmable

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47
Q

what are the characteristics of PROM memory?

A
  • non volatile

- programmed by user by burning fuse, no re-programmable

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48
Q

what are the characteristics of RAM memory?

A
  • VOLATILE
  • information lost when power removed
  • used for short term data storage
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49
Q

what are the characteristics of EPROM memory?

A
  • non volatile
  • UV light used to wipe memory
  • can be re-programmed many times
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50
Q

what are the characteristics of EEPROM memory?

A
  • non volatile
  • electricity used to wipe memory
  • can be reprogrammed many times
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51
Q

what are aircraft computer applications?

A
  • they provide the driving signals to the control surfaces from the flight crew commands in an electrical form
  • take information from the FMS in the form of an autopilot function to fly the aircraft
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52
Q

what type of light is used in fibre optics?

A
  • coherent light
  • in phase
  • monochromatic (one colour)
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53
Q

what two types of core material are used in fibre optics/

A
  • glass - multiple strands, 50 microns in diameter

- plastic - single strands, 0.25 to 1.5 mm in diameter

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54
Q

what three layers form a fibre optic cable?

A
  • core
  • cladding
  • jacket
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55
Q

characteristics of glass fibre optic

A
  • temperature stable

- intolerant to flexing/bending

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56
Q

characteristics of plastic fibre optic

A
  • less temperature stable
  • sensitive to chemicals and solvents
  • tolerant to flexing/bending
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57
Q

what function does the core layer have in fibre optic?

A
  • in the centre

- carries the light

58
Q

what function does the cladding layer have in fibre optic?

A
  • surrounds core layer

- has lower refractive index than core to allow total internal refraction

59
Q

what function does the jacket/coating have in fibre optic?

A
  • protects core and cladding from shocks, contamination and vibration
60
Q

how are fibre optic fibre sizes usually expressed?

A
  • core size followed by cladding size in micro meters

- e.g. 50/125

61
Q

what is the speed of light?

A

3 x 10*8 meters per second

62
Q

what is constructive light wave interference?

A

two light waves in phase, same frequency, adding together

63
Q

what is destructive light wave interference?

A

two light waves out of phase, different frequency, subtracting

64
Q

what are the advantages of fibre optics?

A
  • wide bandwidth
  • low loss
  • immune to electromagnetic interference
  • secure
  • small
  • safe as no voltage
65
Q

what are the disadvantages of fibre optics?

A
  • expensive installation required

- if damaged, may lose many systems

66
Q

what three types of fibre optic couplers are there?

A
  • tee coupler
  • directional coupler
  • star coupler
67
Q

what type of fibre optic coupler would be used if you were required to link many transmitters with many receivers?

A

star coupler

68
Q

what three types of fibre optic cable termination are available?

A
  • physical contact
  • expanded beam
  • pig tail
69
Q

which method of fibre optic cable termination would you most likely find on an aircraft?

A

expanded beam

70
Q

what does a simple CRT display comprise of?

A
  • electron emitter
  • focusing coils
  • x and y deflecting plates
  • phosphor coated screen
71
Q

how does a simple CRT work?

A
  • electrons shot from gun (cathode)
  • attracted to anode (screen)
  • deflected by x (vertical) and y (horizontal) plates
  • electrons hit phosphor screen emitting light (more electrons, more light)
72
Q

in a colour CRT, what is a luminophore?

A
  • red, blue or green luminescent material

- 3 luminophores to each pixel

73
Q

what picture geometry error is created by using a flat screen in a CRT?

A

pincushion distortion

74
Q

what is electrostatic deviation control of electrons given by?

A

plates

75
Q

what is electromagnetic deviation control of electrons given by?

A

coils

76
Q

what ensures that the correct electron beam hits the correct corresponding colour?

A

shadow mask and screen

77
Q

what is the preferred arrangement of the three coloured guns in a CRT?

A

coplanar (side by side)

78
Q

how do you damage a LED?

A

reverse bias 5V

79
Q

how is a colour of an LED determined?

A

doping of semiconductor

80
Q

how is cathode leg of LED determined?

A

flat spot or short leg

81
Q

how do you calculate required resistor value in a LED circuit?

A

(supply voltage - LED voltage)/supply current

82
Q

what is the test figure on a 7 segment LED display?

A

8

83
Q

what are the basics of an LCD display?

A
  • two polarising filters, 90 degrees apart
  • liquid crystal in between
  • when crystal de-energised (in phase), light is twisted - passes
  • when crystal energised (anti phase), light not twisted - doesn’t pass
84
Q

how does damage in an ESSD happen?

A
  • high current raises temperature of internal junctions which causes damage to junction and connecting lines
85
Q

how does static electricity build up?

A

triboelectric effect - transfer of electrons

bad on days with low humidity

86
Q

how do you discharge static in tools when working?

A

touch them to earth regularly

87
Q

what static voltage can be built up by walking over a carpet?

A

100V

88
Q

at what voltage can a static discharge be felt?

A

3000V

89
Q

at what voltage can a static discharge be seen (spark)?

A

12000V

90
Q

what protective devices can be used to prevent damage whilst working with ESSD?

A
  • wrist straps connected to earth through 1M ohm resistor (to prevent bodily harm)
  • component leads shorted together
  • special working areas
  • do not touch exposed conducting pats i.e. IC’s, circuit pathways etc
  • transport in semi-conductive film bags
91
Q

what purpose does the 1M ohm resistor in an ESSD wrist strap serve?

A

share supply voltage reducing damage to the body

92
Q

software management control document number to remember

A

ends in DO-178B

93
Q

software management levels:

A

A (catastrophic) - E (nil effect)

94
Q

what does software management level A mean?

A
  • catastrophic
  • aircraft loss
  • death
95
Q

what does software management level B mean?

A
  • hazardous
  • large safety reduction
  • some death
96
Q

what does software management level C mean?

A
  • major
  • significant safety reduction
  • injury
97
Q

what does software management level D mean?

A
  • minor
  • slight safety reduction
  • no injury
98
Q

what does software management level E mean?

A
  • nil effect
  • does not affect safety
  • no injury
99
Q

how do you reduce electromagnetic environment interference?

A
  • using filters
  • passive - resistors, capacitors
  • active - transistors, diodes
100
Q

what is the relationship between electromagnetic environment interference and frequency?

A

as frequency rises, interference reduces

101
Q

what are the four types of coupling in electromagnetic environment interference?

A
  • inductive (coils)
  • conductive (wires)
  • capacitive (capacitors)
  • radiative (antennas)
102
Q

what is HIRF?

A
  • high intensity radiated fields

- static, lightning etc.

103
Q

how do aircraft deal with HIRF?

A
  • bonding of aircraft parts to provide low resistance pathways and a body which is earth
  • static wicks on trailing edges to reduce static on airframe
104
Q

what are the main causes of HIRF protection degradation?

A
  • corrosion
  • thermal cycling
  • vibration
105
Q

what is considered primary aircraft structure WRT HIRF?

A
  • fuselage
  • wings
  • tailplane
106
Q

what is considered secondary aircraft structure WRT HIRF?

A
  • doors

- opening panels

107
Q

what two EFIS systems are available and what OEM uses each?

A
  • ECAM - airbus

- EICAS - boeing

108
Q

in ECAM (airbus) where do RED warnings and AMBER cautions come from?

A
  • RED warnings come direct from systems

- AMBER cautions come from SDAC (system data acquisition concentrator)

109
Q

in ECAM (airbus), what drives the DU’s?

A

display management computers (DMC)

110
Q

what are the three types of failure on an aircraft?

A
  • independent
  • primary
  • secondary
111
Q

what is an independent failure?

A

failure affects isolated system only, no knock on effect

112
Q

what is a primary failure?

A

failure of system or component which will affect other systems

113
Q

what is a secondary failure?

A

loss of a system or component due to a primary failure

114
Q

what do red and amber CAS messages indicate?

A
  • RED - immediate attention, immediate action

- AMBER - immediate attention, can choose to delay action

115
Q

how many flight management computers FMC are there and how do they operate?

A
  • 2, one in control and other in standby
116
Q

how often are performance and navigation databases updated in the FMC?

A

every 28 days

117
Q

what is VNAV wrt FMC?

A
  • vertical navigation

- e.g.. engine indications, flap config, fuel quantity and flow

118
Q

what is LNAV wrt FMC?

A
  • lateral navigation

- e.g.. IRS, DME, VOR

119
Q

where do the crew input data into the FMC?

A
  • control display units
  • boxed info essential
  • dashed information nonessential but helpful
120
Q

how does fly by wire operate?

A
  • control column input to
  • FCC to
  • data bus to
  • PFCU (flight control unit) to
  • control surface
121
Q

what data bus types do fly by wire use?

A
  • twisted pair of fibre optic

- ARINC 429/629

122
Q

how is safety ensured in fly by wire?

A
  • system is duplicated to prevent redundancy

- i.e. 2 ELAC (elevator and aileron control) computers, one active and one in damping mode

123
Q

how can the crew maintain vertical control if AP fails?

A

elevator trim

124
Q

what is ACARS?

A

aircraft communication, addressing and reporting system

125
Q

where is ACARS used?

A
  • between aircraft and other agency

- i.e. airline operator or air traffic

126
Q

what are the characteristics of ACARS?

A

220 characters, if more needed, multi block message

127
Q

what are the three segments to GPS?

A
  • space
  • ground
  • control
128
Q

how many satellites are in the space segment?

A
  • 24 satellites total (3 spares, 21 active)

- orbiting at 10,900 nm

129
Q

how often are the satellites in GPS updated?

A

every 12 hours (one orbit) from control

130
Q

what is RAIM?

A

receiver autonomous integrity monitoring (satellite health check)

131
Q

WRT RAIM, how many satellites are required to identify failure and to identify source of failure?

A
  • 5 to identify bad information

- 6 to identify source

132
Q

how many satellites are required to give 2d navigation?

A

3

133
Q

how many satellites are required to give 3d navigation?

A

4

134
Q

what is mask angle wrt GPS satellites and what is it set at?

A
  • 7.5 degrees

- eliminates errors from satellites due to slow signal at low elevation (longer time in earths atmosphere)

135
Q

how does a IRS nav system work?

A
  • acceleration integrated once to give velocity
  • acceleration integrated twice to give distance
  • uses NSEW as co-ordinate system, i.e. lat/long
136
Q

what is important for an IRS system to work accurately?

A

correct crew input of starting position

137
Q

how does TCAS operate?

A
  • warns of traffic in the area
  • traffic advisory (yellow) 30 - 45 seconds before collision
  • resolution advisory (red) 20 - 30 seconds before collision
138
Q

resolution advisory will be either…

A
  • corrective i.e. climb

- preventative i.e. dont

139
Q

integrated modular avionics (IMA)

A
  • more redundancy
  • common modules or platforms
  • AFDX (ARINC 664) network, fully duplex
  • speed up to 100Mbits, 10Mbits for safety critical operations
140
Q

Cabin information systems (CIS)

A
  • 3 domains: avionic, flight operations and cabin

- avionics domain is only two way communication

141
Q

air traffic control (ATC)

A

allows crews to send/receive data messages from ATC about clearances/weather etc

Basic Digital Techniques and Electronic Instrument Systems (4 decks)

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