Equipment Flashcards
(152 cards)
1
Q
Which areas of ATC are radio waves used in? (5)
A
- Voice communication (VHF/UHF)
- Navigation (VOR/NDB)
- Surveillance systems
- Weather radar
- Data transmission
2
Q
What is electricity?
A
A form of energy produced by movement of electrons and atoms
N.B. Radio can be used to transmit and receive electromagnetic energy
3
Q
What is Amperes Law?
A
An electric current produces a magnetic field (B) perpendicular to to the flow direction (I)
4
Q
- What are radio waves?
- What speed do radio waves travel at?
- What are the properties of radio waves?
A
- Form of electromagnetic energy, similar in behavior to light waves
- 300,000,000 metres per second (represented by c), same as speed of light
- Properties:
- Capable of passing through a vacuum
- Travel in straight lines (generally)
- Invisible
- Intangible (Can’t touch it)
- Inaudible without specialist equipment
5
Q
What is audio and how does it work with radio?
A
Audio
- Action of one person speaking to another causes air to oscillate
- These movements make eardrum vibrate and mimic the air causing receiving person to hear propagates tone
- Limited in range by how loud one can speak and absorption by materials within range
- Radio overcomes this my using VHF which can be propagated over large distances
- Not in audio spectrum
- Radio transmitters and receivers can hear and broadcast VHF and converts them to audio
6
Q
What is Oscillation?
A
- How the wave changes from maximum minimum
- One complete oscillation is known as 1 cycle
- Shown as a sine wave (see below)
7
Q
What is Amplitude?
A
Maximum displacement or value attained by wave from it’s mean value during a cycle
8
Q
What is Wavelength?
A
- Distance in meters between corresponding points in consecutive waves
- Represented by λ symbol
9
Q
What is Frequency?
A
Number of cycles per second i.e. rate of oscillation measured in Hz
Where
1 KHz = 1,000Hz
1 Mhz = 1,000,000Hz
1 GHz = 1,000,000,000Hz
10
Q
What is the relationship between the Velocity of Electromagnetic waves (C), Frequency (F) and Wavelength (λ)?
A
- Equation showing relationship is below
- The longer the wavelength, the lower the frequency
- The shorter the wavelength, the higher the frequency
11
Q
What is a Carrier Wave?
A
- An electromagnetic wave which can be modulated (varied)
- Produced by a local oscillator
- Modulated (Either FM or AM) in direct proportion to the signal to be transmitted
- Carrier wave is combined with audio wave
12
Q
What is AM and its advantages?
A
Amplitude Modulation
Used to broadcast ATC radio as excellent sound quality not required
Advantages of AM
- Stronger stations can override weaker or interfering stations, and don’t suffer from a capture effect found in FM
- If pilot is transmitting (Tx), control tower can “talk over” that Tx and other ACFT will hear somewhat garbled mixture of both Tx’s rather than just one or other
- A heterodyne (Squeal) will be heard, even if both Tx’s are received with identical signal strength
- No indication of blockage would be evident in FM system
13
Q
What is FM and its advantages?
A
Frequency Modulation
Frequency of the radio carrier is varied in line with the amplitude of the incoming audio signal
Advantages of FM
- Resilience to noise - Any signal level variations will not affect audio output
- Easy to apply modulation at a low power - No boosting of the amplitude required
- Use of efficient RF amplifiers - Means that for a given power output, less battery power required and this makes use of FM more viable for portable two way radio applications
14
Q
What is Attenuation and what causes it?
A
- Reduction in strength of a radio wave with range or time from point of transmission
- With attenuation, amplitude decreases but wavelength and frequency remain unchanged
- The higher the frequency, the greater the attenuation and shorter range
- Caused by ever expanding wave front and resistance from medium radio wave passes through
- Prime factors are gases and vapours, water droplets (cloud, fog and hail)
15
Q
Fill in the table of frequency wavebands
A
16
Q
What is VLF frequency waveband used for and what are its main characteristics?
A
Used for
- Long range communications
- Very long range navigation aids
Main Characteristics
- Requires immense aerials and high transmitter power
- Very prone to static interference
- Waves will bend around objects/follow curvature of the Earth
- Less attenuation
17
Q
What are LF and MF frequency bands used for and what are their main characteristics?
A
Used for
- Reliable, long range communications
- NDB
- Some radio broadcasts
Main Characteristics
- Requires large aerials and high transmitter power
- Prone to static interference and night effect
- Very congested waveband
- Waves will bend around objects/follow curvature of the Earth
- Less attenuation
18
Q
What is HF frequency band used for and what are its main characterstics?
A
Used for
- Long distance wireless telegraphy
- RTF communications
Main Characteristics
- Long range communications by day and night limited by diurnal and seasonal variation of the ionosphere
- Requires smaller aerials and transmitter power
- Suffers from static interference and fading
- Optimum operating frequency varies diurnally
19
Q
What are VHF and UHF frequency bands used for and what are there main characteristics?
A
Used for
- Line of sight communications
- RTF, ILS, VOR, VDF, Surveillance Radar
Main Characteristics
- MAX range dependent upon ACFT height and aerial height
- Small aerial and transmission power
- Free from static interference and easy to suppress on ACFT
- Prone to ducting
- Wavebands become congested
20
Q
What are SHF and EHF frequency bands used for and what are their main characteristics?
A
Used for
- Short range communications
- Precision, Surveillance and Airborne weather Radar
- Radio altimeter
Main Characteristics
- Severe attenuation
21
Q
What is Ducting?
A
- Marked temperature inversion plus a rapid decrease in humidity may form a duct
- Waves bounce between surface and the top of the duct due to ratio of wavelength to duct height
- VHF, UHF and SHF wavebands can travel unusually long distances in these circumstances
22
Q
What does RADAR stand for?
A
RAdio Detection And Ranging
23
Q
What is Radar used for?
A
Area Control
- Wide area
- Terminal control
- Air defence
Approach Control
- Within defined area of responsibility
- Vectoring to final approach
- SRA
Aerodrome control
- Using Aerodrome Traffic Monitor (ATM)
Air
- Traffic integration
- Approach monitoring
- DFTI - Distance from Touchdown Indicator (no longer used)
Ground
- RWY protection
- Monitoring ground movements
- Hazard identification
24
Q
What is Primary Surveillance Radar and how does it work?
A
A system that uses reflected radio signals
How it Works
- Primary radar transmits pulse of radio energy then determines whether any of the energy is reflected
- Position of object that reflected the energy is determined from:
- Direction that the radar aerial was pointing
And
- Time between transmitting the pulse of energy and receiving an echo
25
What is the **Range Equation**?
**Range Equation**
26
What part of the waveband spectrum does ATC Radar operate in?
1mm to 100cm
27
What is one of the biggest factors affecting design of a Radar system for a specific role?
Attenuation of particular wavelengths
N.B. The higher the frequency/shorter the wavelength, the more attenuated due to increased interaction with air molecules
28
What wavelengths are used for **Surface Movement Radar**, **Primary Approach Radar** and **Primary Area Radar**?
- **Surface Movement Radar** - 2-3cm
- **Primary Approach Radar** - 3-10cm
- **Primary Area Radar** - 23-50cm
N.B. Shows how radar designers use principle of longer wavelength for a farther distance
N.B.B. Typical approach radar may transmit around 1200 pulses per second equating to range of about 67 nm
29
1. What is a **PSR Blip**?
2. What causes clutter on a Radar?
1. Visual indication, in non-symbolic form, on situation display of position of an ACFT obtained by primary radar
2. Ground objects and weather
30
Define **Position Indication**
Generic term for visual indication, in non-symbolic and/or symbolic form, on situation display of position of an ACFT, aerodrome vehicle or other object
31
Define **Position Symbol**
Visual indication in symbolic form, on situation display, of position of an ACFT, aerodrome vehicle or other object obtained after automatic processing of positional data derived from any source
32
Define **Radar Contact**
Situation which exists when radar position of a particular ACFT is seen and identified on a situation display
33
Define **Situation Display**
Electronic display depicting position and movement of ACFT and other information as required
34
What are the three basic blocks of a primary radar system?
1. **Transmission - Transmitting energy in a suitable form**
Trigger Unit sends a series of pulses to Modulator (each pulse fires Modulator) which is an ON/OFF switch for the Transmitter, the Transmitter sends a series of pulses to the aerial
2. **Reception - Receiving energy reflected by objects within operational range of system**
Detects reflected signals and amplifies as necessary
3. **Display - Displaying information to the controller**
Boosted clean signal received is displayed on Situation Display
N.B. Duplexer also comes between Transmission and Reception blocks
35
What is a **Duplexer**?
A transceiver, but can only do one thing at a time
36
What is **PRI**?
Pulse Repetition Interval
37
What is **Secondary Surveillance Radar**?
A system of radar using ground interrogators and airborne transponders to determine position of ACFT in range and azimuth, and, when agreed modes and codes ares used, height and identity
38
1. What frequency does the interrogator on the ground transmit signal on?
2. What frequency does transponder on ACFT reply to the above on?
1. 1030 MHz
2. 1090 MHz
39
What wavelength is used for **SSR Radar**?
30cm
40
What modes are used for the SSR interrogation process?
- **Mode A** for identification - transmitted with a pair of pulses 8.5 µs apart
- **Mode C** for vertical position information - transmitted with a pair of pulses 21 µs apart
- ACFT transponder recognises mode by time interval
N.B. Transponder stops transmitting after responding to each interrogation
41
1. In what form does a transponder respond to interrogations?
2. How many bits can be transmitted at a time and why?
3. Which numbers can be used in a squawk and why?
4. How many possible Mode A squawk codes are there?
1. A train of pulses in binary code
2. No more than 12 bits due to processor limitations
3. For Mode A, 4 numbers are needed for a squawk, therefore there are only enough bits to represent the numbers 0-7
4. 4096 possible Mode A discrete squawk codes
42
What does an issuing a squawk code ease the task of?
Identification and monitoring of an ACFTs progress
43
1. Discrete codes are __________
2. Non-discrete codes are __________
1. Issued to individual ACFT
2. Single codes issued to numerous ACFT and Special codes, applied by ACFT on certain occasions
44
What is **CCAMS**?
**Centralised Code Assignment and Management System**
- Developed by EUROCONTROL and endorsed by ICAO
- Insufficient code blocks to develop a world wide system
- Certain countries grouped together into Participating Regions (PAs)
- Europe divided into 7 PAs
45
What are the advantages of CCAMS? (3)
- Reduces RTF and cockpit workload by allocating SSR code which will be retained by ACFT from TKOF to touchdown
- Helps in forward planning, particularly in areas of overlapping radar cover
- Assists in implementation of radar data processing and data exchange programmes
46
What are **Conspicuity Codes**?
- Codes assigned to individual positions to identify ACFT being controlled by a particular unit to another unit, assisting coordination with controlling unit
- Codes may be allocated for special tasks and others may have specific meanings (published in relevant AIP)
47
What are **Special Codes**?
**Agreed internationally to indicate some emergency situations:**
- **7700** - ACFT Emergency (77 Gone to heaven)
- **7600** - Radio Failure (76 Radio in a fix)
- **7500** - Unlawful Interference (75 Staying alive)
48
What pressure setting is used as a reference standard using Mode C?
ISA Standard 1013.25 hPa
49
What is **Garbling** and how can it be overcome?
**False codes may be displayed if ACFT are so close to each other that their responses to Mode A interrogation overlap**
- Occurs when two ACFT are close enough that replies overlap as there is no reliable way to sort them out
- Usually occurs when ACFT are passing above each other
- De-garbler fitted to ground based equipment to overcome this
N.B. One of the main disadvantages of SSR
50
What is **Fruiting** and how can it be overcome?
**FRUIT stands for False Replies Un-synchronised In Time**
- Occurs when interrogator receives a reply from a transponder which was triggered by another interrogator
- Can cause significant issues on an SSR display
- Overcome using a defruiter
N.B. One of the main disadvantages of SSR
51
What is **Antenna Shadowing** and how can it be mitigated?
**Onboard antenna is shadowed by fuselage e.g. due to bank angle**
Mitigated by placing more than one antenna. Generally two; one on top of the ACFT and one on the bottom
52
What is **Monopulse SSR** and its advantages?
**A type of SSR which improves clarity and accuracy and replaced conventional SSR by the 1990’s**
**Advantages**
- Single pulse used and accuracy is improved by averaging measurements made on several or all pulses received in a reply from ACFT
- Fruiting and Garbling are minimised since each pulse is separately labelled with direction and unscrambles two overlapping Mode A or C replies
- The table below compares Standard SSR and Monopulse SSR
53
What is **Resolution**?
The accuracy with which the radar is able to identify range and bearing or azimuth of each target within its range of coverage
N.B. The higher the resolution, the clearer the traffic picture delivered to controllers
54
What factors **determine** radar coverage? 📡📶 (7)
**Both**
- Aerial size, shape and height above ground
- Atmospheric conditions
- Transmitter power
- Receiver efficiency
**Primary Radar Only**
- Size of target
- Pulse Recurrence Frequency (PRF)
- Pulse Length
55
What is the usual ACFT requirement for a radar aerial and what is the width/coverage?
- Narrow beam in azimuth combined with wide beam in elevation
- Usual Beam width is 2-3º which at 60nm would give a coverage of 2-3nm
56
Why must the height of the aerial with reference to wavelength be considered?
- For a given aerial height, the shorter the wavelength, the more gaps in high level coverage but better low level coverage
- Conversely, for a given aerial height, the longer the wavelength, the fewer gaps in high level coverage but poorer low level coverage
57
What radiation pattern does ATC’s radar tend to use?
Cosecant squared
N.B. Optimal service volume of a single radar installation would cover cylindrical area extending up to about 60,000ft with radius of about 200 NM, however much of this is wasted energy transmitted
58
What is the purpose of a vertical coverage diagram?
- Displays theoretical coverage of radar being described
- Takes into account inherent design factors of radar together with general and atmospheric conditions
59
What is a Unit Coverage Diagram (UCD)?
- Shows actual coverage of system after it has been installed
- Takes into account local terrain (hills, valleys etc) and thus unique to each particular installation
- Operational radar procedures are determined from the UCD
60
What factors **affect** radar coverage? (6)
- Absorption/Attenuation due to cloud, fog & hail
- Atmospheric (size of water droplets) bending and/or ducting
- Super refraction/Anomalous Propagation - can produce radar echoes from below normal cover and ranges in excess of those allowed for in design of the radar
- Transmitter power
- Pulse Recurrence Frequency - more hits on targets
- Pulse Length - affects minimum range of primary radar system
61
What are the 2 main methods of removing unwanted returns?
- Moving target indicator
- Circular polarisation
62
What is the purpose of **Circular Polarisation**?
- Utilised by radar to overcome effect of weather clutter
- Only switched on when required as it can mask some returns
- System can be gated to ignore such returns and allow ACFT to be seen
63
What is the purpose of **Moving Target Indicator** (MTI) System?
- Display echoes from moving targets i.e. ACFT and rejects echoes from fixed targets
- Removes ground clutter from radar display
- Successful M.T.I. operation depends upon radial movement of the ACFT between successive radar pulses
- Tangential fading and blind velocity fading can occur
64
What is **Tangential Fading**?
Cancellation of radar blip occurs if ACFT is moving tangentially (90º) to radar beam meaning an ACFTs movement will not have a radial component
N.B. Drawback of Moving Target Indicator (MTI)
65
What is **Blind Velocity Fading**?
- Cancellation of radar blip occurs if ACFT changes its radial distance by half a wavelength during one pulse recurrence interval (i.e. radar path length changes by one wavelength)
- Usually happens when ACFT is flying directly toward or directly away from radar scanner
- Cancellation also occurs when distance is a multiple of half a wavelength
- Speeds at which such fading occurs are known as blind velocities
N.B. Drawback of Moving Target Indicator
66
What does the method used to transmit radar signals depend on?
- The nature of the signals (analogue or digital)
- The distance to be covered
67
Transmission of information using **Coaxial Cables**
- Normally limited to short distances (e.g from perimeter of airfield to control tower)
- Expensive and signal deteriorates rapidly
68
Transmission of information using **Radio Link**
- Operates in UHF-SHF frequency band
- If long distances to be covered, radar information must be suitably monitored and repeated at various stages along route
- To avoid possible interference between links frequency is changed at each radio link repeater
69
Transmission of information using **Telephone Link**
- May be used if of sufficiently high grade and information is being sent in processed form (e.g. digital from plot extractor)
- Can be used over considerable distances and are comparatively cheap to maintain
- Use of plot extractors at radar sites, high grade transmission lines and suitable error checking processes enables high standard of reliability to be maintained
70
Transmission of information using **Fibre Optics**
Used over relatively short distances e.g. between airfield radar site and control tower
71
What medium is used for the transmission of radar data?
**Short Distances** - Coaxial cables and fibre optics
**Long Distances** - Radio link (repeaters) and telephone link
72
What is **Multi Radar Processing**?
Processing information from disparate radar/surveillance sites, presenting on one display in order to reduce or eliminate gaps in radar coverage
N.B. Airspace divided into a grid of squares 16nm x 16nm forming columns of air from the ground upwards. These are called radar sort boxes
73
What is a **Plot Extractor**?
- Decides validity of targets
- Calculates correct azimuth and range data
- Decides if target is primary only, secondary only or combined
- Correlates code data in both identity and height modes
- Checks for emergency, radio fail, SPI indications, etc
- Produces one complete target report per ACFT per aerial revolution and outputs this in digital form
- Produces synchronisation messages
- Produces North mark messages
N.B. Used in Multi Radar Processing
74
What is not improved by a Multi Radar System?
Range and azimuth
75
What moveable data is available with video map?
- DF BEARING LINES
- ELECTRONIC RANGE & BEARING MARKER - ERBM
- ELECTRONIC CURSOR
- SYMBOLS
- ALPHA NUMERICS
N.B. Rolling Ball / Joystick controlled
76
What is **Video Mapping** and what information does it show/include?
The electronic superimposing of a map or plan on a situation display
**Includes**
- SIGNIFICANT POINTS - nav. aids, holding points, etc.
- FINAL APPROACH TRACKS with ranges
- AIRSPACE RESTRICTIONS
- CONTROLLED AIRSPACE BOUNDARIES
- COASTLINES & RIVERS
- FIR &NATIONAL BOUNDARIES
- LATITUDE & LONGITUDE
77
What is Mode S (Select)?
- Co-operative surveillance technique for ATC
- Employs ground based sensors and airborne transponders
- Selectively communicates with individual ACFT
- Operates in same band as conventional SSR (1030-1090 MHz)
- Unique mode S address for each ACFT (24 bit)
- Code allocation by block system to state of registry
- Ground interrogators compatible with Mode A/C
- New ACFT fitted with transponders after 1992 conform to Mode S
78
What are the benefits of Mode S?
- Use of selective interrogation of ACFT reduces FRUITING and GARBLING, hence providing higher integrity radar returns
- Offers data link facility, which will be used to enhance safety by providing Downlink Aircraft Parameters (DAPS)
- DAPS such as ACFT speed, magnetic heading, and altitude to ATCOs and their systems
79
What are the coverage limitations of Mode S?
- Limited by line of sight
- Cone of silence
- MIN and MAX elevations (e.g. 0-60º) depends on antenna design and configuration
80
How many squawk codes are available with Mode S?
**16.75 million through a 24 bit address**
Enables each ACFT to have its own code from registration which reduces fruiting and garbling
81
What are the Mode S phases?
**Operation: Acquisition Phase**
Interrogator tracks conventional transponders and looks for new Mode S transponders and retains in memory individual address for use during Addressed Surveillance Phase
**Addressed Surveillance Phase**
Mode S ACFT are interrogated individually for ATC identification, altitude information and exchange of other data using longer communication messages
82
What are the 2 stages of Mode S being implemented in Europe?
- **ELS** - Mode S Elementary Surveillance
- **EHS** - Mode S Enhanced Surveillance
83
What functionality does **Mode S Elementary Surveillance** (ELS) provide?
**Basic Surveillance functionality**
- 24-bit technical identification
- Mode A code
- Altitude reporting in 25ft increments with Mode C
- Transponder capability reports
- Datalink capability report
- Common usage GICB report (BDS 1,7)
- ACFT Identification - call sign (BDS 2,0)
- Flight status (airborne / on the ground) and including Emergency situations + SPI
- SI-Code functionality
N.B. Position, identification and altitude
84
What do Mode S Elementary Surveillance (ELS) Downlink ACFT Parameters (DAPs) provide the controller with?
- Position
- Identification (Squawk codes can still be used for non-mode S compatible units)
- Altitude
85
What do Mode S Enhanced Surveillance (EHS) Downlink ACFT Parameters (DAPs) provide the controller with?
1. Selected Altitude
2. Roll Angle
3. Track Angle Rate
4. True Track Angle
5. Ground Speed
6. Magnetic Heading
7. Indicated Airspeed (IAS) / Mach no. Note: IAS and Mach no. are considered as 1 DAP, even if technically they are 2 separate ARINC labels. If ACFT can provide both, it must do so
8. Vertical Rate (Barometric rate of climb/descend or baroinertial)
N.B. Basic DAP Set (If Track Angle Rate is available)
86
What operational improvements does the provision of Mode S EHS support?
- Automatic provision of airborne derived data enhances ground system functions including surveillance
- Datalink improves efficiency of communications
- ACFT derived data used by ground based safety nets which enhances ATC decision support
- Maintains and improves quality of surveillance
87
What are the 2 main benefits of Mode S EHS?
Safety and capacity benefits
88
What are the **Safety Benefits** of Mode S? (5)
- Provision of more precise prediction of horizontal and vertical ACFT behaviour i.e. monitoring altitude changes and execution of altitude clearances
- Reduction in risk of communication errors
- Increased situational awareness in high density traffic areas
- Detection of level busts
- Early recognition of ACFT manoeuvres
N.B. PRIDE
89
What are the **Capacity Benefits** of Mode S?
- Reduction of controller and pilot workload
- Direct provision of up-to-date ACFT parameters to controller
- Extension of domain of common reference for pilots and controller
- Reduction of voice channel occupancy
- Improvement of capacity of pre-regulation e.g. sequencing in terminal sectors
- Reducing uncertainty in expected behaviour of ACFT (reduces controller workload)
- Greater anticipation in planning of traffic (improves efficiency)
90
What use can be made of Mode S Multi-lateration?
- Provides accurate surveillance and identification of all transponder equipped ACFT on airport surface.
- Controllers can see each ACFT identification and position on a dedicated screen
- Can supplement or replace GMS/SMR
91
What additional use can be made of Mode S?
- Used in TCAS
- Transponders communicate with each other and decide course of action
- On-board computer retains positions, predicts future positions, and rate closure
- Calculates the closest point of approach (CPA) and produces a two-level warning of proximity
92
Mode S has improved pilot position reporting. True or False?
False
93
What is ADS-B?
**Automatic Dependent Surveillance - Broadcast**
- Means by which ACFT, aerodrome vehicles and other objects can automatically transmit and/or receive identification, position and additional data as appropriate, in a broadcast mode via datalink
- Relies on ACFT/Airport vehicles broadcasting identity, position and other info derived from on-board systems/GNSS etc
94
What is broadcasted by ADS-B and who uses it and what is one of its main limitations?
- Horizontal/vertical position and velocity as well as other information
- Can be used by ACFT to facilitate airborne traffic situational awareness, spacing, separation and self separation (ADS-B In)
- Can also be used by vehicles
- Can also be received by ground facilities (ADS-B Out)
- Enables passive system to monitor, uniquely identify and track all targets in range
- Suitable for ground, and airborne application (For sole-source surveillance)
- Reliant on ALL users providing accurate information ALL of time (LIMITATION)
95
Why is Automatic Dependent Surveillance Broadcast (ADS-B) so named?
- **Automatic** - No external stimulus required
- **Dependent** - Relies on on-board systems to provide **Surveillance** information to other parties
- **Broadcast** - Originating source has no knowledge of who receives data and there is no interrogation or two-way contract
N.B. Surveillance capability in a non-radar environment, plus benefits in E/Route, and at Airfields (SMGS) - it is reliant on all users providing accurate info all of the time
96
What frequency does ADS-B Out use?
1090 MHz (Mode S) using Mode S extended squitter
97
What are the ACFT requirements for ADS-B?
- GPS navigation capability
- Mode-S Transponder
- Avionics capable of providing correct data (usually comes with Enhanced Surveillance capability)
- Correct connections between the three
98
What are the 3 primary types of ADS-B regular broadcasts?
- Position (Surface and airborne)
- Airborne velocity
- ACFT identity
99
What are the 3 various additional “on event” types of message?
- Trajectory
- Status
- Test
100
What are the ADS-B update rates for positions, velocity, on event and flight identity?
- 2 Position Messages Per Second
- 2 Velocity Messages Per Second
- 2 ‘On Event’ Messages Per Second
- 0.2 Flight Identity (i.e. 5s Update)
N.B. Maximum permitted is 6.2 messages per second (mps)
101
What is the maximum and minimum accuracies of ADS-B?
MAX = 7.5m
MIN = Greater than 20nm
102
What can ADS-B be used to overcome?
- SSR aerial shadowing due to terrain
- Can be used to fill gaps in coverage at relatively low cost
- Aid en-route coverage
103
What is **ADS-C** and how does it work?
**Automatic Dependant Surveillance - Contract (Datalink)**
- Relies on specific contracts being established between ground system and ACFTs avionics via datalink
- "C" means that ground system provides ACFT with list of reports to send and specifies when they are required to be sent
**How does it work?**
After receiving logon request, ATSU will need to establish ADS contract(s) with ACFT before it can receive any ADS-C reports
N.B. ADS-C and ADS-B are two different applications
104
What are the 3 types of ADS-C contracts?
- Periodic contract
- Demand contract
- Event contract
105
How does ADS-B utilise satellites?
ADS-B transmissions can be picked up by satellites to provide coverage in remote places where land based receivers are impracticable to install e.g oceans
106
What is **Multi-Lateration** (MLAT)?
- Developing alongside ADS using much of the same technology
- Time Difference of Arrival (TDOA) used to determine accurate position of ACFT or vehicle
- Several MLAT antennae on ground receive broadcasts from ACFT or vehicle mode S transponders
- Position can be displayed on ATC surveillance screens in similar manner to data derived from radar or ADS-B
- Mainly uses squitters for deriving position
- Mainly short-range systems at airport although wide area systems are emerging
- Active interrogation is common
N.B. MLAT is common in Europe
107
How do we obtain MLAT information?
Uses Mode S squitter (self generated automatic burst transmission - giving tracking data)
108
What are the limitations of MLAT?
Similar to SSR and ADS - only detects ACFT or vehicles with Mode S transponders
109
What are the advantages of primary radar over secondary radar? (5)
- **Self-contained** - Needs no external input
- **Independent Operation** - Solely provides identification and fix of ACFT position
- **Non-reliant** - ACFT do not need transponder
- **Permanent Echoes** - Used for calibration
- **Weather Information** – Visually assess significant cloud impact
110
What are the disadvantages of primary radar over secondary radar? (6)
- **No Level Information (or other)** - Only indicates position of ACFT
- **Identification** - Workload and R/T loading increased when using primary radar in order to identify an ACFT (turn
method) and determine its vertical position (asking pilots level)
- **Weather Clutter** - Display may also show weather clutter which can mask returns
- **Permanent Echoes** - Returns from high ground, buildings and high obstacles can block echoes from ACFT (Gloucester Radar is a good example)
- **Range Dependent On** - Transmitter power, target size, target attitude, aspect and target properties
- **No Emergency Indication** - Aside from flying triangles, which has been proved as ineffective
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What are the advantages of secondary radar over primary radar? (6)
- Less transmitter power needed for a similar range
- No ground or weather clutter
- Identification of ACFT simplified and displayed
- Vertical position information displayed
- Emergency squawk codes
- Independent of the equivalent echoing area
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What are the disadvantages of secondary radar over primary radar? (6)
- All ACFT require transponder
- No weather returns
- Fruiting
- Garbling
- Fading
- No permanent echoes for display alignment (calibration)
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What is **STCA**
**Short Term Conflict Alert**
Ground-based safety net intended to assist controller in preventing collisions between ACFT by generating, in a timely manner, an alert of a potential or actual infringement of separation minima (Up to 2 minutes)
114
What is **MTCD**?
**Medium-Term Conflict Detection**
Flight data processing system designed to warn controller of potential conflict between flights in area of responsibility up to 20 minutes ahead
**Consists of**
- **Trajectory Prediction** - responsible for creating future trajectories for each ACFT/target
- **Conflict Detection** - responsible for identifying potentially conflicting trajectories (not necessary the separation minima)
- **Trajectory Update** - responsible for updating predicted trajectories whenever this occurs
- **Trajectory Edition** - responsible for allowing human interaction with predicted trajectory of one or more ACFT/targets
115
What is **MSAW**?
**Minimum Safe Altitude Warning**
- Ground-based safety net which warns controller about increased risk of CFIT accidents by generating, in a timely manner, alerts of ACFT proximity to terrain or obstacles
- Main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima
- MSAW is a part of ATC system and from this perspective can be regarded as a “function”
116
What is **RIMCAS**?
**RWY Incursion Monitor and Collision Avoidance System**
- Fitted to some surface movement surveillance system
- Provides TWR controllers with audio and visual warnings of potential conflictions on RWYs
- PSR and SSR returns can both trigger RIMCAS
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What is **AFDAS**?
**Approach Funnel Deviation Alerting System**
- An approach monitoring aid
- Automatically monitors ACFT on final approach and provides visual and aural alert to TWR controller of any significant lateral or vertical deviation from final approach track or glide path
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What is **CAIT**?
**Controlled Airspace Infringement Tool**
- Radar system monitors squawks and mode C readouts to alert radar controller of any unauthorised entries into controlled airspace
- Primary CAIT (pCAIT) can also detect non squawking ACFT entering CAS which extends upwards from the surface with no upper limit e.g. the London CTR, above which lies the London TMA up to FL 195 and then class C airspace above that
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What is an FMS and its 3 major components?
**Flight Management System**
Computerised avionics component found on most commercial and business ACFT to assist pilots in navigation, flight planning and ACFT control functions
**Three Major Components**
- **FMC** - Flight Management Computer
- **AFS** - Auto Flight System
- **Navigation System** - Including **IRS** (Inertial Reference System) and **GPS**
N.B. EFIS - Electronic Flight Instrument System is not an FMS component, though it is an important interface between FMS and pilots
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What is **CPDLC**?
**Controller Pilot Data Link Communications**
- Datalink application that allows for direct exchange of text messages between controller and pilot
- Improves communication capabilities in oceanic areas, especially in situations where controllers and pilots have previously had to rely on Third Party HF communications
- Supplements many of today's routine voice transmissions
- Allows lots of new information to be sent that alters way air traffic is managed from pre-departure to landing, improving flight safety and efficiency
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What are the contents of CPDLC messages?
- Flight Levels
- Lateral deviations
- Route changes
- Clearances
- Routine delivery of messages
- Crossing contracts
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What are the benefits of CPDLC?
- Allow flight crew to print messages, to give better understanding to foreign pilots
- Allowing auto load of specific uplink messages into the FMS reducing crew-input errors
- Allowing crew to downlink complex route clearances and requests, which ATCO’s can re-send when approved without having to type a long string of coordinates
- Specific uplink messages arm the FMS to automatically downlink report when an event (such as crossing a waypoint) occurs.
- This automation assists with workload management for all
- Some messages will automatically update the Flight Data Record (FDR) in some ground systems
**SI-PAD
- Supplements voice communications
- Improves effiency and safety
- Printed messages
- Auto-load messages without input errors
- Downlink complex routes**
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Who can initiate and cancel an emergency reporting mode in ADS-B?
The flight crew/pilot
124
1. Does a clearance delivered by CPDLC require a specific read back?
2. Does the pilot have to acknowledge a clearance message?
No to both
125
What is **ACARS**?
**ACFT Communication, Addressing and Reporting System**
- Digital data link system for transmission of messages between ACFT and ground stations, in use since 1978
- Modern ACARS equipment now includes facility for automatic as well as manual initiation of messaging
- Uses AM
- Burst transmissions used with a limit of 220 characters per message
- Transmissions often last less than 1 second
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What are the three types of ACARS message and what is it based on?
- **ATC** - Air Traffic Control
- **AOC** - Aeronautical Operational Control
- **AAC** - Airline Administrative Control
Based on content
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What do **ACARS ATC Messages** contain?
- ACFT requests for clearances and ATC issue of clearances and instructions
- Pre-Departure
- Datalink ATIS
- En-route Oceanic Clearances
N.B. ACARS system is currently fulfilling a significant 'niche' role in ATC communications, but not able to be upgraded to functional level of CPDLC due to aged technology and is limited by transmission type ie VHF signals
128
What do **ACARS AOC and AAC Messages** contain?
- Communications between ACFT and its base
- Messages may be of standard form or as defined by users, but all must meet at least guidelines of **ARINC Standard 618**
**Any message content possible including:**
- Final load and trim sheets
- Weather or NOTAM information
- Status, position, ETA, and any diversion of ACFT
- Spot weather observations from ACFT sensors
- Technical performance data including automatically triggered exceedance or abnormal ACFT system status information
- ‘Housekeeping’ Information such as catering uplift requirements, special passenger advice and ETA
- Free text messaging also possible
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What are the benefits of ACARS?
- Automatically sends messages about each phase of flight OOOI msgs (out of gate, off ground, on ground, and into gate)
- Information on ACFT systems in real time
- Interfaces with FMS system for flightplans and weather information
- Utilises VHF, HF and in some cases Satellite links
130
In addition to RTF, what other means of communicating are available to controllers?
- Direct Controller to Controller Communication (Talking)
- Normal Telephone Communication
- Interphone (via controller headset)
- Intercom system
- Mobile telephones
131
What is **ATOTN**?
**Air Traffic Operational Telephone Network**
- Telephone network within the Aeronautical Fixed Service (AFS)
- Used to contact other units connected to AFS
- Airport may only have one line, so only one ATCO can use it at a time, or have one line per position i.e. TWR, RAD
N.B. Potential problem of only having one line
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What is **SELCAL**?
**Selective Calling**
- Signalling method which can alert individual ACFT that a ground station wishes to communicate with it
- RTF replaced by coded tones sent over RTF channels
- Signals can be transmitted over HF or VHF RTF
- Consists of 4 preselected audio tones which take approximately 2 seconds to transmit
- Can relieve flight crew of maintaining listening watch on assigned frequencies which can be especially helpful where RTF still relies on noisy HF channels such as on long haul flights over ocean
- However pilot would have to maintain listening watch if SELCAL was unserviceable
- SELCAL code for ACFT to be included in flight plan
- Ensure that HF aeronautical station has correct code by establishing comms temporarily while still in VHF range
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What should ATCO do in the event of SELCAL call to ACFT remaining unanswered?
After 2 calls on primary frequency and 2 on secondary frequency, revert to voice comms
134
What is **AFS**?
**Aeronautical Fixed Service**
Telecommunication service between specified fixed points provided primarily for safety of air navigation and for regular, efficient and economical operation of air services
135
What is **AFTN**?
**Aeronautical Fixed Telecommunications Network**
Worldwide system of aeronautical fixed circuits provided as part of Aeronautical Fixed Service (AFS) for exchange of messages and/or digital data between stations having same or compatible communications equipment
136
How do we address each AFTN station?
- Each station has its own individual address consisting of 8 letters
- The first 4 are the location identifier followed by the position qualifier
- For example, EGLLZTZX is EGLL Heathrow ZTZ Tower X the printer in the tower
137
What is **MOTNE**?
**Meteorological Operational Telecommunication Network Europe**
The European Meteorological Operations Channel of AFS for exchange of aeronautical meteorological information
138
What characters does AFTN permit the transmission of?
- **Letters** A-Z
- **Numbers** 0-9
- **Signs/special characters** : ; . ‘ / + ? () , =
- Characters other than listed above not to be used in messages unless absolutely necessary for understanding of text. If used, to be spelled out in full
- Roman numerals are not to be used. If originator wishes to indicate that these were intended, normal numbers to be used preceded by the word roman
- Messages shall not contain these abbreviations: **SOH, STX, ETX, ZCZC, NNNN**
- Appropriate abbreviations and codes shall be used rather than plain language
- Non-essential words and phrases such as expressions of politeness shall not be used
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What is the AFTN message transmission priority?
- **1** - SS
- **2** - DD or FF
- **3** - GG or KK
N.B. The person who authorises the transmission signs message to indicate responsibility for assigning priority, although the signature itself is not transmitted
140
What does message priority **SS** mean in AFTN messages?
**Distress Messages and Traffic**
- Grave and imminent danger
- Also includes messages relative to immediate assistance required by mobile station in distress
141
What does message priority **DD** mean in AFTN messages?
**Urgency Messages and Traffic**
- Concerning safety of an ACFT, ship or other vehicle or some person on board or in sight
- Also used for messages requiring special handling meaning that subject matter is of sensitive or restrictive nature
- Not to be used for general ACFT operating agency messages
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What does message priority **FF** mean in AFTN messages?
**Flight Safety Messages**
ATS movement and control messages, and relevant non-ATS messages
**Filed flight plan (FPL)**
- Delay (DLA)
- Modification (CHG)
- Cancellation (CNL)
- Departure (DEP)
- Arrival (ARR)
**Co-ordination**
- Current Flight Plan (CPL)
- Estimate (EST)
- Coordination (CDN)
- Acceptance (ACP)
- Acknowledgement (ACK)
**Supplementary**
- Request Flight Plan (RQP)
- Request Supplementary Flight Plan (RQS)
- Supplementary Flight Plan (SPL) - Search and Rescue - Field 19
**Control**
- Clearance
- Transfer of Control
- Flow Control
- Position Report
- Air Report
**Traffic Information**
**Meteorological info requiring immediate action (SIGMET things)**
**Air Traffic Incident Report**
N.B. All movement and control messages are FF
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What does message priority **GG** mean in AFTN messages?
**Meteorological, Flight Regularity, Aeronautical Administrative and NOTAM messages**
- **Meteorological** - Routine forecasts and observations. Those requiring immediate action are allocated priority indicator FF
- **Flight Regularity** - Information concerning loads, non-routine landings, servicing etc
- **Aeronautical administrative** - Operation or maintenance facilities essential for safety and regularity of ACFT ops
- **Aeronautical administrative** - Efficient functioning of aeronautical telecommunications services
- **Aeronautical administrative** - Between government and civil aviation authorities relating to ACFT operations
- **NOTAMs and SNOWTAMs**
**Operational of Aeronautic Facilities**
**Essential Aerodrome Info**
144
What does message priority **KK** mean in AFTN messages?
**Reservation and General ACFT Operating Agency Messages**
- Passenger and space reservations originated by airline operating agencies
- Any message regarding operation of ACFT not included in one of aforementioned categories
145
What is **OLDI**
**On-Line Data Interchange**
- Protocol for coordination and transfer of current flight date between ATCUs
- Development started din 1990s
- One of major enablers of SESAR
- As required by **Regulation 1032/2006**, it shall be in use by 2009 by all ATCUs
- Reliability at least **99.86%**
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What are the benefits of **OLDI**? (4)
- Automation of routine actions (information exchange) which allows controllers to focus on more complex tasks e.g. conflict detection and resolution
- Reduced controller workload due to reduced need for verbal coordination
- Better situational awareness
- Indirect improvement of ATS system safety features e.g. MTCD
**WISA**
- Workload of controller reduced
- Indirect improvement of ATS System safety features e.g. MTCD
- Situational awareness is better
- Automation of routine actions (information exchange)
147
Besides AFTN, airlines have their own group networks that can be operated in conjunction with AFTN. What are these?
- **OFTS** - Overseas Fixed Telecommunications Service
- **SITA** - Société Internationale Telecommunications Association
148
What does **FourSight** do?
Can identify conflicts up to 18 minutes in advance
149
What is **ExCDS**?
**Extended Computer Display System**
150
What is **iACM**?
**Indra Airspace Capacity Manager**
151
What is **iTEC**?
**Interoperability Through European Collaboration**
152
What is **SWIM**?
**System Wide Information Management**
N.B. Will eventually replace AFTN
