Avionics and operations Flashcards
University
Shortcomings of ANS
ANS = Aircraft navigation system
En route:
1. Mixture of direct tracks, fixed airways or organized tracks
2. Indirect routes
3. Lack of uniformity in procedures
4. Lack of ATC support for advanced on-board systems
Terminal Area & Approach
1. Complexity due to aircraft variation
2. Seperation requirements cause inefficiencies
3. Lack of automation
4. SID/STARs fixed - Indirect routings
5. Noise abatement policies
The current system is incapable of making optimum use of ATC system capacity, available airspace, and aircraft capabilities
AFS and AMS + Communications shortcomings
Aeronautical Fixed Service
ground-ground communication between ATS units
Aeronautical Mobile Service
Air-ground comms bw A/C and ATS units
Air-Air comms bw A/C
Shortcomings:
1. Voice limited
2. Radio wave propagation limitations constrain VHF comms to line-of-sight coverage.
Navigation shortcomings
- Coverage limited due to line-of-sight systems constraining to land and coastal areas.
- Air routes based on navigation aides causing choke points
- Unable to keep up with future air traffic growth
Surveillance shortcomings
- No radar surveillance coverage possible over oceanic /mountaneous areas meaning only procedural ATC support, with little ATFM support
FANS (what are the CNS goals?)
Future Air Navigation System
Communication:
- Network centric data exchange, VHF datalinks, SSR mode S, satellites
Navigation
- GNSS as sole means for navigation
- Trajectory-Based Operations, 4D flight plans, RNP requirements
- Performance-based operations
Surveillance:
- Broadcasting nav. information over ADS-B and SSR mode S
- Shift of ATC tasks toward the flight deck (ACAS and ASAS)
- More automated ATC
VDL
VHF (Very high Frequency) Data Link
SWIM
System Wide Information Management
Jnformation managed and shared between all stakeholders
DownLink:
1. Aircraft flight identification
2. Aircraft navigation state
3. Intended flight plan
UpLink:
1. ATC messages
2. Weather information
3. ATIS (Automatic Terminal Information Service)
GNSS
Global Navigation Satellite System
Needs augmentation
1. on-board (GNSS receiver monitors integrity of navigation signals from GNSS satellites)
2. Local/Regional ground-based reference stations monitor the health of GNSS satellites and determine the range error at its location, which is then transmitted to aircraft (DGPS)
RNP
Required Navigation Performance
Specification of navigation system accuracy required to operate in specified piece of airspace.
ATS provider and Aircraft operator responsible
4D Trajectories
Each aircraft needs to be at a certain location at a specific time. Increasing airspace capacity.
ADS
Automatic Dependent Surveillance
ADS is an on-board avionics function that automatically transmits via digital data link, aircraft position data from the ONS (on-board navigation system) it provides real-time surveillance information to ATS units and other entities in the ATN. It allows surveillance in oceanic and other areas which lack radar or line-of-sight coverage.
- Time of day
- AIrcraft ID
- Position in 3D
- Velocity/Heading
- AIrcraft intent
- Meteorological data
ADS-B
Broadcasts ADS information.
Over continental/coastal: VHF data links (VOR or SSR mode S)
Over remote areas: Satellites
Facilitates ASAS
ASAS, ACAS, and TCAS
Airborne Seperation Assistance System
-Keep aircraft seperated
Airborne Collision Avoidance System
- Airborne system that prevents midair collisions as backup of ATC by alerting flight crew of potential collisions, entirely on board the aircraft. One example is the TCAS
Traffic Collision Avoidance System
-when seperation violation occurs gives warning in form of TA (Traffic Advisory) and RA (Resolution advisory)
Main problems:
1. Lack of precision; only vertical resolutions, not lateral
2. Nuisance warnings due to lack of resolution .
Remember: Use SSR to communicate
FIR definition + organization
Flight Information Region
Airspace around the world is divided into FIRs, which are then subdivided into sectors where each sector has a team of ATC responsible for flow of air traffic.
Organization:
Controlled airspace: ATC, FIS, AL
Uncontrolled airspace: FIS,AL
ATS
Air Traffic Services
ATS = ATM + FIS + AL
Purpose of Air Traffic Services is to enable aircraft operators to meet planned times of departure and arrival and adhere to flight profiles without compromising safety
ATM
Air Traffic Management
ATM = ATC + ASM + ATFCM
ATC
Air Traffic Control
Maintain safe distance between aircraft and obstacles
ASM
Air Space Management
Maximize utilization of available airspace by triage
ATFCM
Air Traffic Flow & Capacity Management
Ensure optimum flow of air traffic when demands exceed capacity of ATC service
FIS
Flight Information Service
Collect, handle, and disseminate flight-related information to assist pilot
Example: ATIS
AL
Alerting Service
Initiate search and rescue for aircraft in distress
ATIS
Automatic Terminal Information Service
Repeated message (VHF) containing information about
- Runway in use
- Transition level (QNE to QNH)
- Weather
- QNH
- Operational issues
Airspace organization
CTR, TMA, CTA, UTA
CTR: Control zone
- Local ATC
TMA: Terminal Control Area
- CTRA - CTA connection
CTA: Control Area
- General ATC, within FIR
UTA: Upper Control Area
- Across FIRs
STAR
Standard Terminal Arrival Route
Defines route flown between ATS route and approach fix. Connects CTA with CTR through TMA
- Noise abatement
- Communication minimisation
- Seperating in and outgoing traffic
- Terrain clearance
ACC
Area Control Center
Controls traffic within CTA
APP
Approach / Departure Control
Provides connection between ACC (CTA) and TWR (CTR)
Incoming traffic from CTA to airport CTR follow STAR’s and outgoing follow SID’s
TWR
Controls air traffic in CTR
- VFR Traffic
- Taxiing
- Traffic ready for departure
- In and outgoing traffic
-Airport surface Detection Equipment (ASDE)
SID
Standard Instrument Departure
Defines route flown between ATS routes (Connects CTR with CTA, through TMA)
- Noise abatement
- Communication minimisation
- Seperating in and outgoing traffic
- Terrain clearance
Radio-transceivers (Voice) types
VHF (Very high frequency)
-limited to Line-of-Sight
HF (High Frequency)
-over-the-horizon
AFTN
Aeronautical Fixed Telecommunications Network
Communication between Air Traffic Services (Flight Plan)
ACARS
Aircraft Communications Addressing and Reporting System
-Between aircraft and airline
Transmitted via VHF radio. Allows airline operator to communicate with aircraft in fleet.
CPDLC
Controller Pilot Data Link Communications.
-Digital messages between Between air traffic controllers and pilots, avoiding need for VDL
Navigation means
-Land routes: VOR/DME
-Long range: INS/GPS
-Main trend: RNAV
RNAV
Area/Random Navigation
Area navigation is a method of navigation which permits the aircraft to navigate along any desired path within coverage of station navigation aides, within limits of self-contained aides, or a combination
Surveillance Means
Continental and Coastal:
-Primary and Secondary surveillance radar
Oceanic and Remote:
-Procedural voice reporting. Pilots must report position to ATC
Primary and Secondary surveillance radar
(PR) Primary Surveillance Radar:
Purpose: slant range, azimuth, radial velocity
-Pulses of radio-frequency energy transmitted and signals scattered back by the surface of an aircraft are received
(SSR) Secondary Surveillance Radar:
Purpose: pressure altitude
-Signal transmitted by this radar initiates transmission of a reply signal from transponder of an aircraft.
Primary Radar + SSR mode A/C provides ATC info about: aircraft position, heading, slant range, altitude, radial velocity, identification
Primary radar limitations
Range resolution: determined by pulse width, ability to distinguish two objects on the same bearing. Objects should be spaced more than half the pulse width
Bearing resolution: Minimum angular seperation at which two objects can be seperated at the same range. Objects should be spaced more than range x beam width.
Minimum range: Pulse width
Maximum range: Pulse repeat time
Maximum range: Rotational velocity
SSR modes
SSR mode A: 8 milliseconds: replies aircraft identification code
SSR mode C: 21 milliseconds: replies aircraft pressure altitude
SSR mode S: Selective, discrete addressing of aircraft unique adress assigned to each aircraft.
SSR side lobes
Weak P2 omnidirectional antenna pulse is given out, if its found to be as strong as P1 and P3 then you are talking to a side lobe.
SSR limitations
- Over-interrogation
Too many interrogating SSRs for one aircraft. - Fruiting
Solved by jitter. Aircraft considers answer to different interrogation as its own - Garbling
Two AC at same time and distance reply to same interrogation, response is garbled
Why Satellite Navigation
- Line of sight coverage over vast areas
- Remote areas reach
- Radio signals penetrate ionosphere overcoming HF radio disadvantages
- Motion of satellites increase chance of good GDOP anywhere on earth
GPS broadcasting Signals
L1 and L2 high frequency carrier signals
PRN (Pseudo Random Noise) Code
-Calculate part of pseudo range by matching received PRN code with database reference to find phase
-Identify which satellite is sending signals
Navigation message
-Position,Velocity,Orbital parameters, Atmospheric model
-HOW (Hand Over Word) contains time the data has been sent by the satellite
First NM –> PRN
GPS Errors
- Satellite clock
(General relativity (Mass) ) or (Special relativity (Velocity) ) - Atmospheric delays
- Solve by atmospheric models or dual frequency - Receiver clocks
-NM and PRN - Multi-path
-filter weak signals - GDOP
-spread out is better
DGPS
Differential GPS
Ground-based receiver to measure GPS timing errors and then provide correct information to nearby receivers
LAAS
Ground-Based Augmentation System
Aircraft landing system based on real-time DGPS
WAAS
Space-Based Augmentation System
Geostationary satellites broadcast correction data to users of GPS satellites
VFR
Visual Flight Rules
IFR
Instrument Flight Rules
DH
Decision Height
Height above runway at which landing must be aborted if the runway is not in sight
RVR
Runway Visual Range
Visibility at the runway surface
ICAO landing categories
Cat I : ILS and Marker beacons, one pilot
Cat II: Dual ILS, radar altimeter, autopilot coupler or dual flight director, two pilots, missed- approach attitude guidance
Cat IIIa: Fail-passive autopilot or head-up display
Cat IIIb: Fail-operational autopilot, automatic rollout
Cat IIIc: Not approved anywhere
ILS
Instrument Landing System
Localizer
-left/right based on phase differences
-end of runway
Glideslope
-up down based on the phase lobes,
remember higher multipath transmitter is smaller lobes
- runway treshold
-False glide slope at 15 deg
Marker beacons
- in front of runway
NILETO (ninety left top) Hz
Radio principle
Wire is placed in space and excited with ALTERNATING CURRENT, power not dissipated in wire is radiated into space, and a similar wire will intercept the power and a detector connected can indicate the magnitude, frequency, phase or time of arrival of the transmitted energy.
Lobe Pattern
Radiation/Reception gain and directional patterns of an antenna
Cone of silence
Inverse cone above radar will not detect any aircraft
Modulation types
PM Pulse modulation (on-off)
FM Frequency Modulation
- not affected by noise
AM Amplitude Modulation
Propagation of Radio Waves
< 3 MHz (<HF) Ground wave
<30 MHz (HF) Sky wave
-not useful for navigation as transmission path is unpredictable
>30 MHz (VHF) Line-of-sight
Reducing Vertical Nulls between Lobes
- Lowering the antenna
- Placing a horizontal Counterpoise
LOP
Line Of Position
- Theta system (VOR)
- Rho system (DME)
- Rho-Theta system, greatest geometrical accuracy
VOR
VHF Omnidirectional Range
Combining an omnidirectional AM signal and a rotating array FM signal for phase comparison.
DME
Distance Measuring Equipment
Active, two-way navigation system, calculates the SLANT RANGE between aircraft and DME station.
Jitter introduced to ensure no syncing with other transmitters. That way other aircraft will see your signal be inconsistent along their measurement periods, whereas for you it is consistently the same after you send it out.
Dead Reckoning System
Derive the state vector from a continuous series of measurements relative to initial position
- Related to inertial navigation systems
- Must be reinitialized to remove accumulated errors
INS
Inertial Navigation Systems
- Stable Platfom
Directly measured in Geodetic inertial frame
-Gyroscopes - Strapdown
Must be algorithmically transformed to geodetic from body
-Optical gyroscopes, MEMS
Advantages:
- Continuously available
- Self-Contained
- Autonomous
- Passive, not jammable
- High accuracy
Disadvantages:
- Expensive
- Error accumulation, must be corriged by GPS
Schuler Tuning
Undamped closed loop corrective action to constrain system tilt errors.
Oscillate around zero value with a 84.4 minute period.
Corrects transport wander by feeding back vehicle rate turns to torque the vertical gyro so the platform follows local vertical.
Optical Gyroscopes
Photon of light send out in CW and CCW directions, when input rate is zero transit time is equal. During rotation, travel length shifts and so doppler effect causes frequency shift, which can be measured. Small jitter effect necessary at low turning rates to prevent light beams from ‘sticking to eachother’ which is filtered out later.
MEMS Gyro
Uses Coriolis effect.
Advantages:
-Small
-Low power consumption
-Inexpensive
-Low maintenance
-Reasonable reliability
Disadvantage: low accuracy
AOM
Aircraft Operating Manual
Contains and describes performance-related data needed for operation of the aircraft.
Flight crew would have to find data for optimal settings for flight conditions and external factors
High pilot workload.
System that manages aircraft performance and guidance along optimal route needed: FMS
FMS
Flight Management System
Drivers:
- Economic benefits
- Pilot Workload
- Growth of air traffic
- Accurate nav sources: GPS, INS
- Computer system capacity
- Ability to connect various subsystems
FMS = FMC + FDSU + CDU
FMC = Flight Management Computer
FDSU = Flight Data Storage Unit
CDU = Command/ Display Unit
FMS is mission critical as opposed to the autopilot which is safety critical, thus these will not be mixed.
FMS tasks
- Flight planning
enables major revisions of the flight plan in flight based on data such as [Radio navaids, waypoints, airways, airports, runways, airport procedures, company routes] - Navigation and Guidance
Combines data from nav sources (INS, GPS, Navaids) to derive best estimate of ac position and velocity. Computes ground speed, track, weather data. - Optimization and performance prediction
FMS selects speed, altitude, and engine power settings during all phases of flight.
Navigation system categories
- Sole means
- Supplemental means
- Primary means
Sole means
Navigation system category:
-For a given phase of flight, must allow aircraft to meet all four navigation system performance requirements
Accuracy, Integrity, Availability, and Continuity of service
(Does not exist yet, INS comes closest)
Supplemental Means
Must be used in conjuction with a sole means navigation system (GPS)
Primary Means
Navigation system that for a given phase of flight must meet accuracy and integrity standards, but not full availability and continuity requirements.
Safety achieved by limiting flights to specific time periods or procedural restrictions. (VOR, DME)
Types of Navigation Systems
- Positioning Systems
-Celestial navigation, mapping
-Radio navigation systems - Dead Reckoning Systems
-Classical DR
-INS
Dead reckoning systems
Derive state vector from a continuous series of measurements relative to initial position
-Classical DR
-Inertial Navigation Systems
Require positioning systems to recalibrate
Navigation Errors
- Sensor errors
- Computer errors
- Data entry errors
- Display errors
- Flight-Technical Errors
1-4: NSE: Navigation System Errors
5: FTE: Pilot error
GDOP
Geometric Dilution of Precision
Navigation error depends on your position
Software Classification
Mission-critical code
Safety-critical code
Software architecture developed to segregate safety and mission critical code from eachother
Cockpit information
- Primary flight info
-Attitude, Airspeed, Altitude, Heading - Airborne systems data
-Hydraulics, Electronic systems - Airframe data
-Undercarriage, Flaps, Slats - Navigation information
-Position, Velocity, Flight-Plan - Engine data
-Thrust, RPM, Fuel-flow - Warning information
-Traffic, Terrain, Weather
Flight instrument positioning
-Basic six (outdated)
-Basic T (new)
Display types
-Additive
One information source, checked incidentally
-Accumulative
Multiple information sources, checked incidentally (can even be two engines)
-Integrative
Multiple information sources, checked continuously
FD
Flight Director
Aircraft Symbol (V-bars)
Command Bars
FD modes
You can set all sorts of commands in the Mode Control Panel: L NAV, VORLOC, lvl chg, hdg sel, app, alt hld, v/s
IF you then choose to use FD you get commands to follow to satisfy these setups yourself.
If you choose to use autopilot the aircraft will move to the specified demands itself.
EFIS
Electronic Flight Instrument System
- HUD
- PFD
- ND
- MFD
- EICAS
- ECAM
- CDU
HUD
Head Up Display
PFD
Primary Flight Display
ND
Navigation Display
MFD
Multi-Function Display
EICAS/ECAM
Engine Indication & Crew Alerting System (boeing)
Electronic Centralised Aircraft Monitor (airbus)
CDU
Command/Display Unit
Magnetic Variation
Angle between LOCAL MAGNETIC MERIDIAN and the GEOGRAPHIC MERIDIAN. If magnetic north lies to east of North it is positive.
Magnetic Dip
Inclination angle of lines of magnetic force with respect to the earth. 0 at magnetic equator and 90 at magnetic poles.
Direct reading compass
Freely suspended. Compass pivot point above center of gravity.
In the northern hemisphere the southern tip goes up and vice versa
ANDS/ASDN
Aircraft going east on northern hemisphere will find that accelerating makes the compass overshoot north and decellerating overshoot south. Vice versa in southern hemisphere
UNOS/ONUS
Aircraft going east on northern hemisphere will find that the compass undershoots when turning north and overshoots when going south and vice versa.
Direct reading compass deficiencies
- Compass must be readable by crew
- No means of obtaining simple electrical input
- Damping action of liquid causes lag in turns
- Erronenous indications during turns and acceleration
Fluxgate Magnetometer
remote compass that uses electro-magnetism principles to convert earth magnetic field into measurable voltage. Solves problems of magnet having to be readable and obtaining simple electrical input from it.
Gyrosyn compass
Magnetic slaving principle.
Combining a magnetic compass (fluxgate magnetometer) and a directional gyroscope solves problems during acceleration and turns.
Magnetometer compensates for deficiencies of directional gyro: namely the drift (long term, low frequency)
Directional gyroscope compensates for deficiencies in magnetometer: namely the errors during accelerations and turning (short term, high frequency)
Geodetic reference frame
NED reference frame but attached to aircraft center of gravity
Body reference frame
Geodetic reference frame including attitude (pitch, roll, yaw/heading)
Rigidity
Property which resists force tending to change direction of spin axis
Precession
Angular change in direction of rotation under influence of an applied force. Change in direction takes place not in line with force but point 90 degrees away in direction of rotation.
Free gyroscope
Gyroscopes which remain a fixed orientation relative to inertial space
Gyroscope compensations necessary
-Apparent drift (rotation of earth)
-Transport wander (movement of vehicle)
fixed by feeding velocity data back
Learn how to derive these
Rate gyroscope
Only one degree of freedom and uses precession property and angular rates
Still needs to be compensated for transport wander
QFE
absolute altitude , 0 when on runway - height above runway
QNE
relative to 101325, - flight levels
QNH
relative to MSL - altitude
