At a glance Flashcards
what is the typical configuration of a cockpit EIS system?
- 6 screens DU’s , driven by 2 DEU’s
- DEU 1 supplies DU’s 1 - 3
what do the DU’s in a typical cockpit EIS system display?
- 2 PFD, attitude, speed, altitude
- 2 ND, map, radar, route planning
- 2 Engine Instruments
in event of loss of power to DU’s or failure, how will the DU’s reorder to display essential information?
- PFD will be displayed at highest priority
- Engine Instruments will be displayed at second highest priority
how would the loss of a DEU be displayed?
Red X displayed across whole of associated DU’s
what does a red X on part of DU indicate?
immediate flight crew action to restore data
what does an amber X on part of DU indicate?
action required but flight crew can choose to delay action
what base is decimal?
10
what base is binary?
2
what base is octal?
8
what base is hexadecimal?
16
binary is split into groups of ____ to convert to octal
3
binary is split into groups of ____ to convert to hexadecimal
4
what do DAC and ADC mean with regards to data conversion?
- DAC - Digital to Analogue Converter
- ADC - Analogue to Digital Converter
how many inputs would a 4-bit DAC have?
4
what is the quantisation interval in a DAC?
- maximum output voltage/maximum binary input
- equivalent to the LSB
what is the quantisation level in a DAC?
- quantisation interval (LSB) x binary input
what is accuracy with regards to data conversion?
- variance in output voltage from predicted voltage
- given in %
what is resolution with regards to data conversion?
- 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
what are the characteristics of a weighted resistor DAC?
- resistors half in size from the LSB upwards
- MSB smallest resistor
what is the main disadvantage of a wighted resistor DAC?
- need a lot of different value resistors = expensive
what are the characteristics of a R2-R resistor DAC?
- resistor branch (2 resistors) for each binary unit
what is the main advantage of a R2-R resistor DAC?
- only need 2 values of resistor = cheap
what is sampling rate with regards to data conversions?
- higher sampling rate = smaller quantisation level = good reproduction
how does a successive approximation DAC work?
- 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
how does a fast parallel ADC work?
- 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
what does a data bus do?
transfers data from point a to point b using digital signals
what types of data transmission are there?
- simplex
- half duplex
- full duplex
how does simplex data transmission work?
only goes in one direction
how does half duplex data transmission work?
goes in both direction but only one direction at a time
how does full duplex data transmission work?
goes in both directions simultaneously
why types of aircraft data bus are there?
- ARINC 429
- ARINC 629
what are the characteristics for ARINC 429?
- 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
what are the characteristics of ARINC 629?
- 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
what types of gates are there?
- AND
- OR
- NOT
- NAND
- NOR
- EXOR
- EXNOR
how do you calculate the number of outputs in a logic gate?
2n where n in the number of inputs
the general purpose computer has 4 main sections, what are they?
- CPU, memory types, databuses and input/output devices
what does the CPU (central processing unit) contain?
- ALU (arithmetic and logic unit)
- bus interface
- timing and control unit
what is the purpose if the ALU within the CPU
to carry out arithmetic and logic
what is the purpose of the bus interface unit within the CPU?
moves information and commands through the data buses in the computer
what is the purpose of the timing and control unit within the CPU?
maintains timing and control of the systems to stop information from crashing
what three data buses are there within a basic computer?
- address bus
- data bus
- timing and control
what is the function of the address bus within a computer?
- ONE WAY data flow from CPU to ROM, RAM, I/O
what is the function of the data bus within a computer?
- TWO WAY data flow from/to CPU to ROM, RAM, I/O
what is the function of the timing and control bus within a computer?
- ONE WAY signal flow from CPU to ROM, RAM, I/O
what 5 types of memory are available in a computer?
- ROM
- PROM
- RAM
- EPROM
- EEPROM
what are the characteristics of ROM memory?
- non volatile
- programmed at manufacture, not re-programmable
what are the characteristics of PROM memory?
- non volatile
- programmed by user by burning fuse, no re-programmable
what are the characteristics of RAM memory?
- VOLATILE
- information lost when power removed
- used for short term data storage
what are the characteristics of EPROM memory?
- non volatile
- UV light used to wipe memory
- can be re-programmed many times
what are the characteristics of EEPROM memory?
- non volatile
- electricity used to wipe memory
- can be reprogrammed many times
what are aircraft computer applications?
- 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
what type of light is used in fibre optics?
- coherent light
- in phase
- monochromatic (one colour)
what two types of core material are used in fibre optics/
- glass - multiple strands, 50 microns in diameter
- plastic - single strands, 0.25 to 1.5 mm in diameter
what three layers form a fibre optic cable?
- core
- cladding
- jacket
characteristics of glass fibre optic
- temperature stable
- intolerant to flexing/bending
characteristics of plastic fibre optic
- less temperature stable
- sensitive to chemicals and solvents
- tolerant to flexing/bending
what function does the core layer have in fibre optic?
- in the centre
- carries the light
what function does the cladding layer have in fibre optic?
- surrounds core layer
- has lower refractive index than core to allow total internal refraction
what function does the jacket/coating have in fibre optic?
- protects core and cladding from shocks, contamination and vibration
how are fibre optic fibre sizes usually expressed?
- core size followed by cladding size in micro meters
- e.g. 50/125
what is the speed of light?
3 x 10*8 meters per second
what is constructive light wave interference?
two light waves in phase, same frequency, adding together
what is destructive light wave interference?
two light waves out of phase, different frequency, subtracting
what are the advantages of fibre optics?
- wide bandwidth
- low loss
- immune to electromagnetic interference
- secure
- small
- safe as no voltage
what are the disadvantages of fibre optics?
- expensive installation required
- if damaged, may lose many systems
what three types of fibre optic couplers are there?
- tee coupler
- directional coupler
- star coupler
what type of fibre optic coupler would be used if you were required to link many transmitters with many receivers?
star coupler
what three types of fibre optic cable termination are available?
- physical contact
- expanded beam
- pig tail
which method of fibre optic cable termination would you most likely find on an aircraft?
expanded beam
what does a simple CRT display comprise of?
- electron emitter
- focusing coils
- x and y deflecting plates
- phosphor coated screen
how does a simple CRT work?
- 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)
in a colour CRT, what is a luminophore?
- red, blue or green luminescent material
- 3 luminophores to each pixel
what picture geometry error is created by using a flat screen in a CRT?
pincushion distortion
what is electrostatic deviation control of electrons given by?
plates
what is electromagnetic deviation control of electrons given by?
coils
what ensures that the correct electron beam hits the correct corresponding colour?
shadow mask and screen
what is the preferred arrangement of the three coloured guns in a CRT?
coplanar (side by side)
how do you damage a LED?
reverse bias 5V
how is a colour of an LED determined?
doping of semiconductor
how is cathode leg of LED determined?
flat spot or short leg
how do you calculate required resistor value in a LED circuit?
(supply voltage - LED voltage)/supply current
what is the test figure on a 7 segment LED display?
8
what are the basics of an LCD display?
- 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
how does damage in an ESSD happen?
- high current raises temperature of internal junctions which causes damage to junction and connecting lines
how does static electricity build up?
triboelectric effect - transfer of electrons
bad on days with low humidity
how do you discharge static in tools when working?
touch them to earth regularly
what static voltage can be built up by walking over a carpet?
100V
at what voltage can a static discharge be felt?
3000V
at what voltage can a static discharge be seen (spark)?
12000V
what protective devices can be used to prevent damage whilst working with ESSD?
- 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
what purpose does the 1M ohm resistor in an ESSD wrist strap serve?
share supply voltage reducing damage to the body
software management control document number to remember
ends in DO-178B
software management levels:
A (catastrophic) - E (nil effect)
what does software management level A mean?
- catastrophic
- aircraft loss
- death
what does software management level B mean?
- hazardous
- large safety reduction
- some death
what does software management level C mean?
- major
- significant safety reduction
- injury
what does software management level D mean?
- minor
- slight safety reduction
- no injury
what does software management level E mean?
- nil effect
- does not affect safety
- no injury
how do you reduce electromagnetic environment interference?
- using filters
- passive - resistors, capacitors
- active - transistors, diodes
what is the relationship between electromagnetic environment interference and frequency?
as frequency rises, interference reduces
what are the four types of coupling in electromagnetic environment interference?
- inductive (coils)
- conductive (wires)
- capacitive (capacitors)
- radiative (antennas)
what is HIRF?
- high intensity radiated fields
- static, lightning etc.
how do aircraft deal with HIRF?
- 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
what are the main causes of HIRF protection degradation?
- corrosion
- thermal cycling
- vibration
what is considered primary aircraft structure WRT HIRF?
- fuselage
- wings
- tailplane
what is considered secondary aircraft structure WRT HIRF?
- doors
- opening panels
what two EFIS systems are available and what OEM uses each?
- ECAM - airbus
- EICAS - boeing
in ECAM (airbus) where do RED warnings and AMBER cautions come from?
- RED warnings come direct from systems
- AMBER cautions come from SDAC (system data acquisition concentrator)
in ECAM (airbus), what drives the DU’s?
display management computers (DMC)
what are the three types of failure on an aircraft?
- independent
- primary
- secondary
what is an independent failure?
failure affects isolated system only, no knock on effect
what is a primary failure?
failure of system or component which will affect other systems
what is a secondary failure?
loss of a system or component due to a primary failure
what do red and amber CAS messages indicate?
- RED - immediate attention, immediate action
- AMBER - immediate attention, can choose to delay action
how many flight management computers FMC are there and how do they operate?
- 2, one in control and other in standby
how often are performance and navigation databases updated in the FMC?
every 28 days
what is VNAV wrt FMC?
- vertical navigation
- e.g.. engine indications, flap config, fuel quantity and flow
what is LNAV wrt FMC?
- lateral navigation
- e.g.. IRS, DME, VOR
where do the crew input data into the FMC?
- control display units
- boxed info essential
- dashed information nonessential but helpful
how does fly by wire operate?
- control column input to
- FCC to
- data bus to
- PFCU (flight control unit) to
- control surface
what data bus types do fly by wire use?
- twisted pair of fibre optic
- ARINC 429/629
how is safety ensured in fly by wire?
- system is duplicated to prevent redundancy
- i.e. 2 ELAC (elevator and aileron control) computers, one active and one in damping mode
how can the crew maintain vertical control if AP fails?
elevator trim
what is ACARS?
aircraft communication, addressing and reporting system
where is ACARS used?
- between aircraft and other agency
- i.e. airline operator or air traffic
what are the characteristics of ACARS?
220 characters, if more needed, multi block message
what are the three segments to GPS?
- space
- ground
- control
how many satellites are in the space segment?
- 24 satellites total (3 spares, 21 active)
- orbiting at 10,900 nm
how often are the satellites in GPS updated?
every 12 hours (one orbit) from control
what is RAIM?
receiver autonomous integrity monitoring (satellite health check)
WRT RAIM, how many satellites are required to identify failure and to identify source of failure?
- 5 to identify bad information
- 6 to identify source
how many satellites are required to give 2d navigation?
3
how many satellites are required to give 3d navigation?
4
what is mask angle wrt GPS satellites and what is it set at?
- 7.5 degrees
- eliminates errors from satellites due to slow signal at low elevation (longer time in earths atmosphere)
how does a IRS nav system work?
- acceleration integrated once to give velocity
- acceleration integrated twice to give distance
- uses NSEW as co-ordinate system, i.e. lat/long
what is important for an IRS system to work accurately?
correct crew input of starting position
how does TCAS operate?
- warns of traffic in the area
- traffic advisory (yellow) 30 - 45 seconds before collision
- resolution advisory (red) 20 - 30 seconds before collision
resolution advisory will be either…
- corrective i.e. climb
- preventative i.e. dont
integrated modular avionics (IMA)
- more redundancy
- common modules or platforms
- AFDX (ARINC 664) network, fully duplex
- speed up to 100Mbits, 10Mbits for safety critical operations
Cabin information systems (CIS)
- 3 domains: avionic, flight operations and cabin
- avionics domain is only two way communication
air traffic control (ATC)
allows crews to send/receive data messages from ATC about clearances/weather etc
