Aircraft Radio Navigation Communication Systems 3l6s46
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Air Waves in Aviation
Radio transmission is an electromagnetic wave with the same characteristics as light or heat.
Wavelength is the linear measurement of the wave.
Cycle is the interval in which the wave rises and falls between its crest and trough.
Frequency is the number of cycles/second.
Amplitude is the strength of the signal.
RADIO FREQUENCY BANDS 3 kHz to 30 kHz
Very Low Frequencies (VLF)
30 kHz to 300 kHz
Low Frequencies (LF)
300 kHz to 3,000 kHz
Medium Frequencies (MF)
3,000 kHz to 30,000 kHz
High Frequencies (HF)
30,000 kHz to 300,000 kHz
Very High Frequencies (VHF)
300,000 kHz to 3,000,000 kHz Ultra High Frequencies (UHF)
Propagation: How Signals Travel Propagation On The HF Bands Ground-wave Propagation Sky-wave Propagation HF Scatter Propagation VHF/UHF Propagation Characteristics Line-of-sight Propagation Tropospheric Bending and Ducting VHF/UHF Signals Through The Ionosphere
T3-6
Radio waves travel to their destination in four ways: 1.
Line of Sight
2.
Ground-Wave
3.
Along the ground, bending slightly to follow the Earth’s curvature.
Tropospheric Bending and Ducting
4.
Directly from one point to another.
In the lower layer of the Earth’s atmosphere.
Sky-Wave
Refracted or bent back to the Earth’s surface by ionized layers in the ionosphere.
T3-7
Both the VHF and HF system utilize transmitters, receivers and antennas. Transceivers are units that include both the transmitter and receiver in
one unit. VHF and HF systems are completely independent of each other and utilize their own transmitters, receivers and antennas.
VHF systems are found in any aircraft capable of two way radio communication and are largely used for controlling traffic. HF systems are found in large transport category aircraft that may need to communicate over large distances (overseas).
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Line Of Sight (LOS) Tropospheric Bending Tropospheric Ducting VHF/UHF Signals Through The Ionosphere Sporadic “E”
T3-9
Anytime radio waves are used to follow a path over the ground. Types
VORs
NDB/ADF GPS
Uses Guidance during times of reduced visibility Establish orientation Enhance Situational Awareness
Region Troposphere
Height 7 miles
Stratosphere 6 to 30 miles
Ionosphere
30 to 400 miles
Notes Region where all weather occurs
Region where atmospheric gases “spread out” horizontally. The high speed jet stream travels in the stratosphere. Region where solar radiation from the sun creates ions. Major influence on HF radio wave propagation.
T3-15
T3-16
Ground-Wave Propagation Sky-wave Propagation HF Scatter Mode
T3-17
Results from a radio wave diffraction along the Earth’s surface. Primarily affects longer wavelength radio waves that have vertical polarization (electric field is oriented vertically). Most noticeable on AM broadcast band and the 160 meter and 80 meter amateur bands. Communication distances often extend to 120 miles or more. Most useful during the day at 1.8 MHz and 3.5 MHz when the D-Region absorption makes sky-wave propagation impossible. T3-18
The curved surface of the Earth horizon can diffract long-wavelength (low frequency) radio waves. The waves can follow the curvature of the Earth for as much as several hundred miles.
T3-19
Ionization levels in the Earth’s ionosphere can refract (bend) radio waves to return to the surface. Ions in the Earth’s upper atmosphere are formed when
ultraviolet (UV) radiation and other radiation from the sun knocks electrons from gas atoms. The ionization regions in the Earth’s ionosphere is affected the sunspots on the sun’s surface. The sunspots vary in number and size over a 11 year cycle.
Sky-wave propagation is determined by radio wave frequency and level of ionization in the ionosphere.
T3-20
Communication distances of 2500 miles are possible with one skip off the ionosphere. Skip propagation has both minimum and maximum
ranges. The area between the maximum ground wave distance and the minimum skip distance is called the skip zone. World-wide communications is possible using several skips (or multi-hops)
The highest frequency that a radio wave transmitted straight up is reflected back to Earth is called the critical frequency.
T3-21
The maximum usable frequency (MUF) is the highest frequency at which the ionosphere bends radio waves back to a desired location on earth. MUF is dependant on level of solar radiation strength and time of day. The maximum usable frequency (MUF) tends to be higher during periods of high sunspots.
T3-22
T3-23
The Earth’s ionosphere contains several regions of charged particles which affect radio signal propagation. The ionization regions change from day to night periods.
Region
Height Above Surface
D Region
30-60 miles
E Region
60-70 miles
F Region
100-310 miles
T3-24
D Region Height about 35 to 60 miles above Earth. Maximum ionization at or near noon. Ionization disappears by sunset.
Absorbs energy from radio waves. Absorption on lower
frequencies is greater than higher frequencies. Radio wave absorption is most pronounced at mid-day. Responsible for short daytime communication ranges on lower-frequency HF bands (160, 80 and 40 meters).
T3-25
E Region Height about 50 to 70 miles above Earth. Ionization useful for bending radio waves when in sunlight. Reaches maximum ionization level around midday. Ionization reaches a minimum level just prior to sunrise. Radio wave propagation up to about 1250 miles in a single skip hop. T3-26
F Region Height ranges from 100 to 310 miles above Earth. Ionization reaches a maximum about noon and tapers off
gradually toward sunset. Minimum ionization is reached just prior to sunrise. F region splits into two parts (F1 and F2) during the day and recombine at night. ▪ F1 region forms about 140 miles above Earth ▪ F2 region forms about 200 miles above Earth
F2 region is responsible for long distance HF band
communication with distances of about 2500 miles. T3-27
All electromagnetic wave propagation is subject to scattering influences from the Earth’s atmosphere, ionospheric regions and objects in radio path. Scattered signals may be received in sky-wave propagation skip zone. Scatter signals are generally weak and subject to echoes and distortion. Most common when operating near the MUF. Under ideal conditions, scatter propagation is possible over 3000 miles or more. T3-28
Back Scatter Propagation
T3-29
Radio signals travel in a straight line from a transmitting antenna to the receiving antenna. Provides VHF/UHF communications within a 100 miles or so. Signals can be reflected by buildings, hills, airplanes, etc. Reflections vary the propagation path causing signal cancellation and reinforcement. This results in a rapid fluttering sound called picket fencing.
T3-30
T3-31
Slight bending of radio waves occur in the troposphere close to the Earth’s surface. There is always a radio signal loss as radio waves travel
through the troposphere ▪ Radio signal loss increases as the frequency increases
The radio path horizon is generally 15 percent farther
away than the visible horizon (typically 8 to 9 miles). ▪ Communication distances can be increased by increasing the antenna height above the terrain
Tropospheric bending propagation is most useful at 144
Mhz and higher frequencies
T3-32
The farthest point to which radio waves will travel directly. The structure of the atmosphere near the Earth’s surface causes the radio waves to bend in a curved path. The radio horizon exceeds the geometric horizon by approximately 15%.
T3-33
The distance D to the radio horizon is greater from a higher antenna. The maximum distance over which two stations may communicate by space wave is equal to the sum of their distances to the horizon. T3-34
Distance(miles)
Chart shows theoretical communication distance (in miles) to the radio horizon for various transmitter antenna heights above terrain (in feet). 50.0 45.0 40.0 35.0 30.0 25.0 20.0 15.0 10.0 5.0 0.0 1.0 D 1.415 x H
10.0
100.0
1000.0
Height(ft)
T3-35
Radio signals can also be trapped in the troposphere, traveling a long distance before returning to the Earth’s surface. Results when a “duct” is formed by a temperature inversion level (warm air over cold air) over land or water. Adjacent tropospheric regions having different densities will bend
radio waves ing through the regions
Most useful at VHF/UHF frequencies. Most frequent during spring, summer and fall. Can provide s of 950 miles or more over land and up to 2500 miles over ocean
T3-36
When a cool air mass is overrun by a mass of warmer air, a “duct” may be formed, allowing VHF and UHF radio signals to travel great distances with little attenuation or signal loss.
T3-37
Sporadic E A type of sky-wave propagation that allows long distance
communication on the VHF bands (6 meters, 2 meters and 220 Mhz) through the E region of the atmosphere. Occurs only sporadically during certain times of the year. Most common type of VHF atmospheric propagation. The 6 meter band is most likely experience sporadic-E propagation during the summer months ... even during periods of low sunspot activity.
T3-38
VHF HF ACARS / AIRCOM Secal decoders SATCOM
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Two types commonly used for communication: VHF ▪ VHF (very high frequency) is used by air traffic control and operates in the VHF band between 118 and 136.975 MHz ▪ Range is 30 miles at 1000 feet and approximately 135 miles at 10,000 feet HF ▪ HF (high frequency) used for extended range communication operates between 2.0 and 29.999 MHz References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Transmits short messages from aircraft systems to central facility in Chicago Two modes used Demand mode – Flight crew transmits Polled mode – Ground station transmits
Note: AIRCOM is the European and Australian equivalent
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Used to “filter” messages on COMM radio receivers Aircraft are assigned a tone combination for secal unit to monitor. Secal unit alerts the crew to an incoming radio transmission
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Utilizes satellites for transcontinental flight communications More reliable the HF communication Range is between latitudes 75º N and 75º S Uses three sub-systems Ground earth station Aircraft earth station Satellite system
Capable of of transmitting information from many different sources AIRCOM, ACARS, flight-crew communications, enger telephone,
telex and fax
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
NDB/ADF Ground Equipment – NDB: Non – Directional Beacon • Refers to the actual station of ground
Airborne Equipment – ADF: Automatic Direction Finder • Refers to instrument found in the airplane
Nondirectional Radio Beacon (NDB) Transmits same signal in all directions
Directional/Loop Antenna Rotates to find the most powerful signal Sense Antenna Receives equal signal throughout System uses both antennas to figure out where you are in relation to the station
ADF Receives NDB Signals in (190-535)kHz AM Broadcast Low Band
Relative Bearing What is read from the Indicator Degrees from nose of aircraft to the station
Magnetic Heading What is read from the Heading Indicator Degrees from North to nose of aircraft
Magnetic Bearing Where you are in relation to the station Degrees from north to the station
RB + MH = MB
Tracking Inbound
000
350
Wind Wind 350
010
010
53
350
000
Tracking Outbound
Wind Wind
340
340
015
54
Navigation Procedures • Homing – Keep the nose of the aircraft always pointing to the station – Needle always be aligned – Does not take into wind
55
WHEATON 326 ETH
1.
2.
Where is the station in relation to me? look at the ADF needle - Relative bearing
What direction am I going? look at heading indicator - Magnetic heading
3.
4.
Where am I in relation to the station? North, South, East, or West?
What course would I fly to get to the station?
Homing Keep the nose of the aircraft always pointing to the station Needle always be aligned Does not take into wind
Ground Equipment Airborne Equipment Principle : Bearing measurement by “PHASE DIFFERENCE”
Very High Frequency Range 108.0-117.95 Transmits two signals Reference Phase ▪ Same all the way around Variable Phase ▪ Rotates at 1800 RPM Measures Phase Difference
360 different radials, that can each be flown in 2 directions Is not heading sensitive
Altitude Class of facility Terrain
off flag appears Morse Code no longer heard Inoperative CDI
Corrective Actions ADF GPS Radar vectors (flight assist)
Omnibearing Selector (OBS) Course Deviation Indicator (CDI) To-From Indicator
Parts of a VOR system Receiver Course Deviation Indicator (CDI) To/From ind.
Omni bearing selector
•VHF ANTENNA
•VHF RECEIVER 118.00 136.97 USE
KX 155 TSO
STBY
108.00 117.95 USE
COMM
NAV
BENDEX / KING
OFF
PULL TEST
STBY
PULL IDENT
Identifying the Station Interpreting the VOR Indications Reverse Sensing Off Indications Tracking Intercepting a Course Cross Checking Position
Must do prior to using the VOR Ensure correct station is selected
Ensure station is working
Morse code identification
Turn the OBS so that the CDI is aligned Make sure that it has a FROM indication Draw out where you are in relation to the station 090
0
30
90
270
60
300
0 33
0
24
0
12
180 KING
0
21
0
OBS
16
FROM
Selected Course FROM
OFF
TFROM Selected Course: 360o
OFF
OFF
TO
Crossbar
From Envelope
To Envelope TO
TO
OFF
VHF Omnirange
Where are you in relation to the station?
0
OBS
180
KING
Where are you in relation to the station?
180 0
OBS
180
KING
If wrong course is set in… Needle will move farther away when correcting Make sure that OBS course matches Aircraft Heading If you want to head TO the station line up TO indication If you want to head FROM the station line up FROM Indication
Reasons for OFF indications Cone of Confusion Out of Range/Unreliable 90° from selected course
0
0
30
90
270
60
300
33
0
24
0
12
180 KING
0
21
0
OBS
16
Cone of Confusion
Zone of Ambiguity
"A" and "B" signal received Only "A" signal received
Only "B" signal received Neither "A" or "B" received
VOR station "A"
VOR station "B"
Fly from one point to the other keeping the CDI centered Bracket by keeping a stabilized crosswind correction
Draw out which way you need to turn to intercept Turn to heading and set OBS to desired radial Track inbound on new radial
Use two VORs to find your exact position Center both VORs with a from indication Draw out the radials
Where they cross is where you are at
Advantages
Limitations
Concise form of
Line of Sight
Navigation Easy to interpret position Not heading sensitive Provides multiple courses TO/FROM the station
Range
Advantages Not limited to Line of
Sight Simple form of Navigation
Limitations Errors ▪ ▪ ▪ ▪
Quadrantal error Night effect Terrain effect Precipitation static
Heading sensitive
Combination of several systems to provide pilot with the ability to land in conditions with poor visibility.
Localizer – indicates alignment w/ runway
Glideslope – indicates correct descent path
Outer Marker – Final Approach Fix
Middle Marker – Missed Approach Point
Needle indicates direction of runway. Centered Needle = Correct Alignment
Needle indicates above/below glidepath. Centered Needle = Correct Glidepath
Correct Glidepath Descent Cone
Runwa
OM – Denotes beginning of final approach segment (Final Approach Fix).
MM – Denotes Missed Approach Point (MAP) Usually placed at decision height on glidepath. “If you can’t see the runway yet, go around.”
Represented by indicator lights with accompanying aural tone in cockpit.
When glideslope is unavailable, pilots may still make a localizer-only approach.
VOR ADF ILS LOC GS Marker beacons
Radio altimeters DME GPS Transponders ELT
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
VOR’s operate between 108.0 to 117.9 MHz frequency band System includes
VOR ground station or transmitter VOR receiver in aircraft ▪ In light aircraft this is often combined with the comm radio
Aircraft display ▪ ▪ ▪ ▪
CDI course deviation indicator TO/FROM indicator OBS omni-bearing selector or course selector ON/OFF flag to determine field strength
Antenna
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
VOR station continually transmits an infinite number of radials. The VOR receiver in the aircraft receives the signal and operates the visual indicator. The pilot determines the bearings of VOR station with respect to the aircraft.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Operation The ADF receives NDB (non-directional beacon)
signals in the 19 to 535 kHz AM broadcast low band. The ADF display pointer (RMI or radio magnetic
indicator) will indicate the relative bearing to the selected AM band in that range.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Combination of several systems to provide pilot with the ability to land in conditions with poor visibility. Components LOC (localizer) ▪ Horizontal reference GS (glide slope) ▪ Vertical reference Marker beacon ▪ Distance from runway Radio altimeter ▪ Very accurate altitude measurement DME (distance measuring equipment) ▪ Very accurate distance measurement
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Combined with the VOR system Utilizes 1 of 40 ILS channels between 108.10 to 111.95 MHz. Operation
The ground transmitter is located at the far end of the
runway and provides a valid signal up to 18 NM The CDI (course deviation indicator) gives full fly left/right deviation of 700 feet at the runway threshold.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Utilizes 1 of 40 channels between 329.15 to 335.00 MHz. Operates on the same principles as the LOC.
The GS transmitter is located between 750 and 1250 ft.
from the approach end of the runway and is offset 250 to 650 ft. The indicator is either an ADI (attitude-director indicator) or HSI (horizontal-situation indicator). ▪ Both indicators combine other indications for ease of use.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Marker beacon receivers operate at 75 MHz and sense the audio signature of 3 types of beacons. Blue outer marker (5 miles from end of runway) ▪ Modulated with 400 Hz Amber middle marker (2/3 mile from end of runway) ▪ Modulated with 1300 Hz White inner marker (1500 feet from end of runway) ▪ Modulated with 3000 Hz
Operation As the aircraft flies over each maker the appropriate light will flash
and an audible sound may be heard.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
The radio altimeter provides better accuracy then the pressure sensitive altimeters. Operation
The transmitter sends out a VHF signal downward then
receives the reflected signal. The transmitter-receiver unit calculates the time needed for the signal to transmit and return to obtain AGL (above ground level) altitude. DH (decision height) used for instrument landings may be incorporated in this system.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Range is up to 199 NM at the high end of controlled airspace based on line of sight with accuracy of ½ mile or 3% of the distance. DME operates on frequencies from 962 to 1213 MHz. Operation
The aircraft transmitter sends out paired pulses at specific spacing. The ground station receives the pulses and then responds with paired
pulses at the same spacing but a different frequency. The aircraft receiver measures the time it takes to transmit and receive the signal which is transmitted into distance.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Utilizes a 24 hour satellite system that is accurate within 100 meters and is unaffected by weather. Has 3 independent segments
Space segment – satellites Control segment – ground based monitoring segment – aircraft
Database updating and antenna maintenance are the primary concerns to the GPS . Will be the most widely used system in the near future.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
An automatic receiver and transmitter that can receive a signal (be interrogated) from a ground station and send a reply back to the station. Used to identify aircraft on radar
Identification or squawk is 1200 for VFR flight Squawk assigned by ATC for IFR flight Used for emergency transmissions
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Three modes of operation Mode A ▪ Location only, non-altitude reporting Mode C ▪ Location and altitude reporting Mode S ▪ Can do Mode A and C and also responds to TCAS (traffic collision avoidance systems)
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Required on all aircraft to provide a signal on crash landings that will enable search aircraft or ground stations to locate the aircraft. Consists of a dual frequency radio transmitter and battery power supply with a whip antenna. Transmits on international distress signals of 121.5 (civil) and 243.0 (military) MHz. Activated by impacts of 5g or more or manually. Transmits up to 100 miles at receiver altitude of 10,000 ft for 50
continuous hours.
Located in an area of the aircraft where impact damage will be minimal. Tail cone area Aft top of cabin
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Three switch positions: AUTO, OFF and ON Testing may be done under the following conditions: Tune VHF COMM receiver to 121.5 MHz Only within the first 5 minutes of an hour Only three pulses should be activated Listen for an audible signal when switched to ON position
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
The battery pack must be changed in accordance with the date stamped on the unit. The battery pack must also be replaced or recharged when it has been in use for more than one cumulative hour, or when 50% of the useful life or charge has expired. Testing should be performed regularly. Inspections must be made every 12 calendar months. Regulations FAR Part 91.52 References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
System inspections Antenna inspections Static discharge inspections Operational checks or any additional inspections required by the manufacturer
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Inspect the condition and security of equipment including wiring bundles. Check for any indications of overheating in the equipment or wiring. Check for poor electrical bonding Requirements are specified by the manufacturer.
Cables should be kept as short as possible, except antenna cable
which have a specific length determined in installation. Proper bonding on the order of .003 ohms is important to the
performance of avionics equipment.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Check instruments and radios for secure attachment to the instrument . Check that all avionics are free of dust or contaminates. Equipment ventilation openings must not be obstructed. Check all plugs, connectors, switches, controls for operation and condition.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Check all instruments for placards as needed. Check all instrument lighting and annunciator lights for operation. Check circuit breaker for placards labeling each circuit breaker installed.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Check for: broken or missing antenna insulation lead through insulators Safety wires
Cracked antenna housing Missing or poor sealant at base of antenna
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Check for: Correct installation Signs of corrosion
Condition of paint/bonding and grounding Bonding of each antenna from mounting base
to the aircraft skin. ▪ Tolerance 1 ohm, maximum References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Check for: Physical security of mounting attachments, wear or abrasion of wicks, missing wicks, etc. Assurance that one inch of the inner braid of flexible vinyl cover wicks extends beyond the vinyl covering. Assurance that all dischargers are present and securely mounted to their base.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Check for: Assurance that all bases are securely bonded to the skin of the aircraft. Any sign of excessive corrosion or deterioration of the discharger tip. Any lighting damage shown by pitting of the metal base. The ohm value of the static wick itself per manufacturer’s instructions. References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Transponder Per FAR 14 Part 91.411 and 91.413 ELT Per FAR Part 91.52 Functional checks of all other COMM and NAV systems per the manufacturer’s instructions
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Ground station oriented to magnetic north, transmitting directional information to aircraft Benefits
More accurate, precise flying Reliable Not susceptible to interference Voice Capable
Errors/Negatives
Costly to maintain Line-of-sight
Omnidirectional reference signal Directional signal from antenna rotating @ 1800 rpm Receiver uses phase discrimination Navigation in polar coordinates (rho-theta)
Distance Measuring Equipment (DME) & often Tacan are colocated with VOR
VHF – 108.0-117.95mhz Line of sight
1 LOP at a time 2 receivers give 2 LOPs (fix) VOR + DME = LOP & Arc (fix)
Not sensitive to aircraft heading Fly to or from a VOR or intercept a radial Radial – courses oriented FROM the station
High
1,000 – 14,500; 40NM 14,500 – 18,000; 100NM 18,000 – 45,000; 130NM 45,000 – 60,000; 100NM
Low
1,000 – 18,000; 40NM
Terminal
1,000 – 12,000; 25NM
* All altitudes AGL
360
Magnetic North
045
315
135º 270
090
135
225
180
VOR receiver gives 1 LOP called a Radial
Receiver Course Deviation Indicator (CDI) To/From ind.
Omni bearing selector
Initial Tracking Tune, Identify, Twist Turn OBS to center needle and figure out position (use FROM) Note heading on top of card ▪ If flying FROM station (radial), then turn to that heading ▪ If flying TO station, put reciprocal heading on top and center, then turn to that heading
Wind Correction Further away, more correction is needed to get back on track ▪ At 60NM from station, 1° = 1NM Generally, when within 20NM, 20-30° in direction of needle works Once needle centers, turn back towards original heading, but add wind correction of 5°
Station age CDI will become very sensitive, and then begin to oscillate Flag will switch from TO/OFF/FROM Switching Radials During station age, turn OBS to new course to fly
Intercepting If needle is alive, then turn towards it as if you were
tracking it If full deflection, first center needle to find what radial you are on Twist OBS back to desired course Parallel that course Turn 30-60 in direction of needle, depending on distance from station Once needle is alive, turn back in direction of desired course Follow tracking procedures
Radio signal sent out from aircraft to ground station. Ground station interprets this signal and sends back. Equipment in aircraft measures time and converts to nautical miles. Errors Diagonal (slant-line) distance from station to aircraft – not lateral ▪ Becomes greater the closer you get to the station ▪ Greatest when directly over station at high altitudes ▪ Limited number of queries
Uses ▪ Intersections/Fixes ▪ IAP ▪ Groundspeed
Pilotage Dead Reckoning Radio Navigation ADF
VOR/DME/RNAV
Electronic Navigation
Loran GPS Inertial
Celestial
Generic name for a system that permits point-topoint flight Onboard computer that computes a position, track, and groundspeed VOR/DME Loran GPS Inertial
Collection of antennas throughout the United States transmit signals Aircraft receiver calculates position based on intersection of multiple signals
GPS = Global Positioning System A space based, all-weather, jam resistant, continuous operation, worldwide radio navigation system. Provides extremely accurate 3D location data as well as velocity and time.
System of 24 satellites, 4/5 of which are in view at all times Receiver uses 4 of these to determine position of aircraft Each satellite transmits code, which contains satellite position and GPS time Receiver, knowing how fast signal was sent and at what time, calculates position
RAIM – Receiver Autonomous Integrity Monitoring Determines if satellites are providing correct data
WAAS – Wide Area Augmentation System Collection of ground receivers take satellite data and
correct it for atmospheric conditions Works based on known position of ground stations
LAAS – Local Area Augmentation System Same as WAAS, but on a smaller, more precise scale For terminal area around airport
Single range can lie anywhere on a sphere
Courtesy of Leica Geosystems
R1
Two ranges will intersect on a line, defined by the intersection of two spheres
Courtesy of Leica Geosystems
Three spheres intersect at a point Three ranges needed to resolve lat/long/altitude
Courtesy of Leica Geosystems
Civilian Uses Marine Navigation Air Navigation Surveying Search and Rescue Collision avoidance Agriculture
Military Uses Marine Navigation Air Navigation Rendezvous Close Air Mine Warfare Unmanned Aerial Vehicles (UAVs)
Dead-Reckoning Self-contained source of: Position, groundspeed, & heading Does not even need a receiver Cannot be jammed Gets better with use Applies a calibration correction after each flight
s(t ) a (t )dt
2
Acceleration is vectorially summed in x, y, & z. Output is compensated movement of the platform & for curvature & rotation of the earth.
Early systems required precise mechanical parts Bigger is more accurate
Modern systems can be: Mechanical (platform) Simple gyros Accurate
Electronic (strap-down) Few moving parts Smaller Cheaper
Aircraft systems use Pendulum accelerometers or MEMS ▪ Micro-electromechanical sensors Ring laser gyros ▪ To measure angular change INS complements GPS
Mechanical
Ring Laser Gyro
Pilotage Dead Reckoning Radio Navigation ADF VOR/DME/RNAV
Electronic Navigation
Loran GPS Inertial
Celestial
Advantages No power required Self contained Cannot be jammed Available everywhere
Disadvantages Dusk & dawn only Clear weather only Slow for aircraft Needs the art of nav. Navigator’s skill
Requires computation At least data entry
Circle of Equal Altitude DeRemer & McLean Global Navigation
Error increases with distance VOR/DME, ADF
Error increases with time DR, Inertial
Reliability Concerns GPS, Loran, Celestial
Human error
1. 2. 3.
Pilotage Dead Reckoning Radio Navigation ADF VOR/DME/RNAV
4. 5.
Celestial Electronic Navigation Loran GPS Inertial
Be suspicious. Check and recheck. If you cannot tell your engers your ETA at the destination, you are not navigating.
Assume you’re near your DR position Do not assume a huge wind just came up Use your VOR/DME or 2 VORs Look on the chart for landmarks Especially those that are shown small If you miss a checkpoint, hold your heading & look for the next one Do not guess where you are! If all else fails, CALL ATC (after all, YOU are paying for it)
Frequency Band: Airborne: 1025 MHz – 1150 MHz Ground :
63 MHz below Tx frequency 1025 – 1087 MHz 63 MHz above Tx frequency 1088 – 1150 MHz This gives 126 channels but two codings are used (X and Y) which doubles the capacity
As the name implies , DME provides information on the distance from the aircraft to the ground station Used to establish position along an airway and also to establish hold points
Frequency Band: Airborne: 1025 MHz – 1150 MHz Ground :
(L band) 63 MHz below Tx frequency 1025 – 1087 MHz 63 MHz above Tx frequency 1088 – 1150 MHz
This gives 126 channels but two codings are used (X and Y)
which doubles the capacity
General Principle: Airborne transceiver transmits a pair of pulses (spaced at 12μs for mode X and 30μs for mode Y)
Ground transmitter receives the pulses, waits 50μs and then
transmits another pair of pulses back to the aircraft Airborne transceiver measures the time between transmission and reception, subtracts the 50μs, multiplies by the speed of light and divides by 2.
This is very simple but gets more complicated when we want to service more than one aircraft We need a method of distinguishing among the signals from up to 100 aircraft. This is done essentially by generating a random set of pulses and correlating with the replies to determine the correct ones.
•Distance •Speed
•Time to Station Notes: 1. The last two are valid only if the aircraft is going directly towards or away from the ground station. 2. The DME measures SLANT RANGE to the station.
Altitude Ground Range
The ground station simply receives a pulse pair, inserts the 50 μs delay and retransmits it. To reduce the effects of reflections it will not reply to another interrogation for about 60 μs (dead time)
The ground station transmits 2700 pulse pairs per second regardless of the number of aircraft interrogating. The extra pulse pairs are called “squitter” If there are not enough interrogations to make up 2700 pulse pairs, the ground receiver increases its sensitivity until noise pulses trigger enough replies to make up the difference If there are too many interrogations, the receiver decreases its sensitivity so that the weakest interrogations get ignored
Using squitter has the following advantages: • The transmitter average output power is constant •The receiver AGC has a constant average signal to work with
•The ground receiver sensitivity is maintained at the optimum level •In the case of overload, the aircraft farthest from the station are dropped off first.
Using squitter has the following advantages:
• The transmitter average output power is constant •The receiver AGC has a constant average signal to work with •The ground receiver sensitivity is maintained at the optimum level
•In the case of overload, the aircraft farthest from the station are dropped off first.
Accuracy: The ICAO specification for DME is 0.5NM or 3% of distance Tests done on Canadian DMEs show that their errors are less than 30m. Integrity DME ground stations are equipped with monitors which can detect erroneous delays and out-of-tolerance power output levels. These shut the system down if and error is detected
Availability: As with most systems there is a standby transmitter which takes over when the main one fails. availability is well above 99.9%
Availability: As with most systems there is a standby transmitter which takes over when the main one fails. availability is well above 99.9%
ILS
Non-precision approaches supply the pilot with horizontal guidance only. (VOR, NDB, Localizer, Loc. B/C, GPS without VNAV) Precision approaches supply the pilot with horizontal and vertical guidance. (ILS, MLS, PAR, GPS with VNAV) ILS is the primary international precision approach system approved by ICAO and protected until 2010. ILS provides an aircraft with precision horizontal and vertical guidance to the runway.
Localizers operate in the VHF range and provide horizontal course guidance to runway centerline. Transmitters are located on the centerline at the opposite end of the runway from the approach threshold.
The signal transmitted consists of two fan shaped patterns that overlap at the centre. The overlap area provides the on-track signal.
The angular width of the beam is between 3°and 6°. Normally width is 5°, resulting in full scale deflection at 2.5°. The width of the beam is adjusted to be 700 feet wide at runway threshold.
The localizer may be offset from runway centerline by up to 3°. Localizers offset more than 3° will have an identifier beginning with X, aligned localizer identifiers begin with I.
A cautionary note will be published in the CAP whenever localizer is offset more than 3°.
Normal reliable coverage of localizers is 18nm within 10° of either side of course centerline and 10nm within 35°. Localizer installations provide back course information, and non-precision localizer back course approaches may be published. (ignore all glide path information on back course) Normally glide path will flag off. Caution: a localizer signal is transmitted differently than a VOR radial. Aircraft receivers are not supplied with azimuth information relative to magnetic or true north. It is simply a beam aligned with the runway centerline. For this reason CDIs will display normal sensing characteristics when flying in the same direction as front course alignment, but reverse sensing when traveling in the direction of back course alignment. (HSI will normal sense anytime front course direction is set on head of track bar.)
Glide path information is paired with the associated localizer frequency. The glide path is normally adjusted to an angle of 3° (may be adjusted 2° to 4.5°) and a beam width of 1.4°(0.7° for full scale deflection). The antenna array is located approx. 1000ft from the approach end of the runway and offset approx. 400ft. (if glide path is followed to the pavement touchdown point will be at the 1000ft markers) In installations with an ILS serving both ends of a runway the systems are interlocked so only one can operate at a time. Note: on a standard 3° glide path 320ft/1nm can be used to .
Typical final approach fixes are NDBs in Canada, but can also be identified by DME or VOR radial and DME as published. Fan Markers are commonly used in the US as a means of identifying aircraft location along a localizer. As the marker is reached a fan marker light will illuminate in the flight deck (if equipped).
CAT I: operation down to a minimum of 200ft DH and RVR2600 or ½ sm ground visibility when RVR not available.
CAT II: operation down to a minimum of 100ft DH and RVR 1200ft.
CAT III: minimums will be prescribed in the carrier’s operating specifications, carriers operations manual, or the CAP. (minimums are further broken down into A,B, or C with a CAT IIIC minimums being zero-zero).
Requirements: CAT II/III approaches require specific aircraft and airport capabilities. (ex: airport lighting, aircraft autoland)
Note: when CAT II/III approaches are being conducted the CAT II or CAT III hold line must be adhered to.
The following must be fully serviceable to meet CAT II/III standards: Airport lighting:
approach lights runway threshold lights touchdown zone lights centerline lights runway edge lights runway end lights all stop bars and lead-on lights essential taxiway lights
ILS components: localizer glide path
RVR equipment: CAT II- two transmissometers- approach end, mid-field
CAT III- three transmissometers- approach end, mid-field,
departure end
Power source: Airport emergency power as primary power source for all
essential system elements. Commercial power available within one second as a backup.
Radio transmission is an electromagnetic wave with the same characteristics as light or heat.
Wavelength is the linear measurement of the wave.
Cycle is the interval in which the wave rises and falls between its crest and trough.
Frequency is the number of cycles/second.
Amplitude is the strength of the signal.
RADIO FREQUENCY BANDS 3 kHz to 30 kHz
Very Low Frequencies (VLF)
30 kHz to 300 kHz
Low Frequencies (LF)
300 kHz to 3,000 kHz
Medium Frequencies (MF)
3,000 kHz to 30,000 kHz
High Frequencies (HF)
30,000 kHz to 300,000 kHz
Very High Frequencies (VHF)
300,000 kHz to 3,000,000 kHz Ultra High Frequencies (UHF)
Propagation: How Signals Travel Propagation On The HF Bands Ground-wave Propagation Sky-wave Propagation HF Scatter Propagation VHF/UHF Propagation Characteristics Line-of-sight Propagation Tropospheric Bending and Ducting VHF/UHF Signals Through The Ionosphere
T3-6
Radio waves travel to their destination in four ways: 1.
Line of Sight
2.
Ground-Wave
3.
Along the ground, bending slightly to follow the Earth’s curvature.
Tropospheric Bending and Ducting
4.
Directly from one point to another.
In the lower layer of the Earth’s atmosphere.
Sky-Wave
Refracted or bent back to the Earth’s surface by ionized layers in the ionosphere.
T3-7
Both the VHF and HF system utilize transmitters, receivers and antennas. Transceivers are units that include both the transmitter and receiver in
one unit. VHF and HF systems are completely independent of each other and utilize their own transmitters, receivers and antennas.
VHF systems are found in any aircraft capable of two way radio communication and are largely used for controlling traffic. HF systems are found in large transport category aircraft that may need to communicate over large distances (overseas).
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Line Of Sight (LOS) Tropospheric Bending Tropospheric Ducting VHF/UHF Signals Through The Ionosphere Sporadic “E”
T3-9
Anytime radio waves are used to follow a path over the ground. Types
VORs
NDB/ADF GPS
Uses Guidance during times of reduced visibility Establish orientation Enhance Situational Awareness
Region Troposphere
Height 7 miles
Stratosphere 6 to 30 miles
Ionosphere
30 to 400 miles
Notes Region where all weather occurs
Region where atmospheric gases “spread out” horizontally. The high speed jet stream travels in the stratosphere. Region where solar radiation from the sun creates ions. Major influence on HF radio wave propagation.
T3-15
T3-16
Ground-Wave Propagation Sky-wave Propagation HF Scatter Mode
T3-17
Results from a radio wave diffraction along the Earth’s surface. Primarily affects longer wavelength radio waves that have vertical polarization (electric field is oriented vertically). Most noticeable on AM broadcast band and the 160 meter and 80 meter amateur bands. Communication distances often extend to 120 miles or more. Most useful during the day at 1.8 MHz and 3.5 MHz when the D-Region absorption makes sky-wave propagation impossible. T3-18
The curved surface of the Earth horizon can diffract long-wavelength (low frequency) radio waves. The waves can follow the curvature of the Earth for as much as several hundred miles.
T3-19
Ionization levels in the Earth’s ionosphere can refract (bend) radio waves to return to the surface. Ions in the Earth’s upper atmosphere are formed when
ultraviolet (UV) radiation and other radiation from the sun knocks electrons from gas atoms. The ionization regions in the Earth’s ionosphere is affected the sunspots on the sun’s surface. The sunspots vary in number and size over a 11 year cycle.
Sky-wave propagation is determined by radio wave frequency and level of ionization in the ionosphere.
T3-20
Communication distances of 2500 miles are possible with one skip off the ionosphere. Skip propagation has both minimum and maximum
ranges. The area between the maximum ground wave distance and the minimum skip distance is called the skip zone. World-wide communications is possible using several skips (or multi-hops)
The highest frequency that a radio wave transmitted straight up is reflected back to Earth is called the critical frequency.
T3-21
The maximum usable frequency (MUF) is the highest frequency at which the ionosphere bends radio waves back to a desired location on earth. MUF is dependant on level of solar radiation strength and time of day. The maximum usable frequency (MUF) tends to be higher during periods of high sunspots.
T3-22
T3-23
The Earth’s ionosphere contains several regions of charged particles which affect radio signal propagation. The ionization regions change from day to night periods.
Region
Height Above Surface
D Region
30-60 miles
E Region
60-70 miles
F Region
100-310 miles
T3-24
D Region Height about 35 to 60 miles above Earth. Maximum ionization at or near noon. Ionization disappears by sunset.
Absorbs energy from radio waves. Absorption on lower
frequencies is greater than higher frequencies. Radio wave absorption is most pronounced at mid-day. Responsible for short daytime communication ranges on lower-frequency HF bands (160, 80 and 40 meters).
T3-25
E Region Height about 50 to 70 miles above Earth. Ionization useful for bending radio waves when in sunlight. Reaches maximum ionization level around midday. Ionization reaches a minimum level just prior to sunrise. Radio wave propagation up to about 1250 miles in a single skip hop. T3-26
F Region Height ranges from 100 to 310 miles above Earth. Ionization reaches a maximum about noon and tapers off
gradually toward sunset. Minimum ionization is reached just prior to sunrise. F region splits into two parts (F1 and F2) during the day and recombine at night. ▪ F1 region forms about 140 miles above Earth ▪ F2 region forms about 200 miles above Earth
F2 region is responsible for long distance HF band
communication with distances of about 2500 miles. T3-27
All electromagnetic wave propagation is subject to scattering influences from the Earth’s atmosphere, ionospheric regions and objects in radio path. Scattered signals may be received in sky-wave propagation skip zone. Scatter signals are generally weak and subject to echoes and distortion. Most common when operating near the MUF. Under ideal conditions, scatter propagation is possible over 3000 miles or more. T3-28
Back Scatter Propagation
T3-29
Radio signals travel in a straight line from a transmitting antenna to the receiving antenna. Provides VHF/UHF communications within a 100 miles or so. Signals can be reflected by buildings, hills, airplanes, etc. Reflections vary the propagation path causing signal cancellation and reinforcement. This results in a rapid fluttering sound called picket fencing.
T3-30
T3-31
Slight bending of radio waves occur in the troposphere close to the Earth’s surface. There is always a radio signal loss as radio waves travel
through the troposphere ▪ Radio signal loss increases as the frequency increases
The radio path horizon is generally 15 percent farther
away than the visible horizon (typically 8 to 9 miles). ▪ Communication distances can be increased by increasing the antenna height above the terrain
Tropospheric bending propagation is most useful at 144
Mhz and higher frequencies
T3-32
The farthest point to which radio waves will travel directly. The structure of the atmosphere near the Earth’s surface causes the radio waves to bend in a curved path. The radio horizon exceeds the geometric horizon by approximately 15%.
T3-33
The distance D to the radio horizon is greater from a higher antenna. The maximum distance over which two stations may communicate by space wave is equal to the sum of their distances to the horizon. T3-34
Distance(miles)
Chart shows theoretical communication distance (in miles) to the radio horizon for various transmitter antenna heights above terrain (in feet). 50.0 45.0 40.0 35.0 30.0 25.0 20.0 15.0 10.0 5.0 0.0 1.0 D 1.415 x H
10.0
100.0
1000.0
Height(ft)
T3-35
Radio signals can also be trapped in the troposphere, traveling a long distance before returning to the Earth’s surface. Results when a “duct” is formed by a temperature inversion level (warm air over cold air) over land or water. Adjacent tropospheric regions having different densities will bend
radio waves ing through the regions
Most useful at VHF/UHF frequencies. Most frequent during spring, summer and fall. Can provide s of 950 miles or more over land and up to 2500 miles over ocean
T3-36
When a cool air mass is overrun by a mass of warmer air, a “duct” may be formed, allowing VHF and UHF radio signals to travel great distances with little attenuation or signal loss.
T3-37
Sporadic E A type of sky-wave propagation that allows long distance
communication on the VHF bands (6 meters, 2 meters and 220 Mhz) through the E region of the atmosphere. Occurs only sporadically during certain times of the year. Most common type of VHF atmospheric propagation. The 6 meter band is most likely experience sporadic-E propagation during the summer months ... even during periods of low sunspot activity.
T3-38
VHF HF ACARS / AIRCOM Secal decoders SATCOM
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Two types commonly used for communication: VHF ▪ VHF (very high frequency) is used by air traffic control and operates in the VHF band between 118 and 136.975 MHz ▪ Range is 30 miles at 1000 feet and approximately 135 miles at 10,000 feet HF ▪ HF (high frequency) used for extended range communication operates between 2.0 and 29.999 MHz References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Transmits short messages from aircraft systems to central facility in Chicago Two modes used Demand mode – Flight crew transmits Polled mode – Ground station transmits
Note: AIRCOM is the European and Australian equivalent
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Used to “filter” messages on COMM radio receivers Aircraft are assigned a tone combination for secal unit to monitor. Secal unit alerts the crew to an incoming radio transmission
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Utilizes satellites for transcontinental flight communications More reliable the HF communication Range is between latitudes 75º N and 75º S Uses three sub-systems Ground earth station Aircraft earth station Satellite system
Capable of of transmitting information from many different sources AIRCOM, ACARS, flight-crew communications, enger telephone,
telex and fax
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
NDB/ADF Ground Equipment – NDB: Non – Directional Beacon • Refers to the actual station of ground
Airborne Equipment – ADF: Automatic Direction Finder • Refers to instrument found in the airplane
Nondirectional Radio Beacon (NDB) Transmits same signal in all directions
Directional/Loop Antenna Rotates to find the most powerful signal Sense Antenna Receives equal signal throughout System uses both antennas to figure out where you are in relation to the station
ADF Receives NDB Signals in (190-535)kHz AM Broadcast Low Band
Relative Bearing What is read from the Indicator Degrees from nose of aircraft to the station
Magnetic Heading What is read from the Heading Indicator Degrees from North to nose of aircraft
Magnetic Bearing Where you are in relation to the station Degrees from north to the station
RB + MH = MB
Tracking Inbound
000
350
Wind Wind 350
010
010
53
350
000
Tracking Outbound
Wind Wind
340
340
015
54
Navigation Procedures • Homing – Keep the nose of the aircraft always pointing to the station – Needle always be aligned – Does not take into wind
55
WHEATON 326 ETH
1.
2.
Where is the station in relation to me? look at the ADF needle - Relative bearing
What direction am I going? look at heading indicator - Magnetic heading
3.
4.
Where am I in relation to the station? North, South, East, or West?
What course would I fly to get to the station?
Homing Keep the nose of the aircraft always pointing to the station Needle always be aligned Does not take into wind
Ground Equipment Airborne Equipment Principle : Bearing measurement by “PHASE DIFFERENCE”
Very High Frequency Range 108.0-117.95 Transmits two signals Reference Phase ▪ Same all the way around Variable Phase ▪ Rotates at 1800 RPM Measures Phase Difference
360 different radials, that can each be flown in 2 directions Is not heading sensitive
Altitude Class of facility Terrain
off flag appears Morse Code no longer heard Inoperative CDI
Corrective Actions ADF GPS Radar vectors (flight assist)
Omnibearing Selector (OBS) Course Deviation Indicator (CDI) To-From Indicator
Parts of a VOR system Receiver Course Deviation Indicator (CDI) To/From ind.
Omni bearing selector
•VHF ANTENNA
•VHF RECEIVER 118.00 136.97 USE
KX 155 TSO
STBY
108.00 117.95 USE
COMM
NAV
BENDEX / KING
OFF
PULL TEST
STBY
PULL IDENT
Identifying the Station Interpreting the VOR Indications Reverse Sensing Off Indications Tracking Intercepting a Course Cross Checking Position
Must do prior to using the VOR Ensure correct station is selected
Ensure station is working
Morse code identification
Turn the OBS so that the CDI is aligned Make sure that it has a FROM indication Draw out where you are in relation to the station 090
0
30
90
270
60
300
0 33
0
24
0
12
180 KING
0
21
0
OBS
16
FROM
Selected Course FROM
OFF
TFROM Selected Course: 360o
OFF
OFF
TO
Crossbar
From Envelope
To Envelope TO
TO
OFF
VHF Omnirange
Where are you in relation to the station?
0
OBS
180
KING
Where are you in relation to the station?
180 0
OBS
180
KING
If wrong course is set in… Needle will move farther away when correcting Make sure that OBS course matches Aircraft Heading If you want to head TO the station line up TO indication If you want to head FROM the station line up FROM Indication
Reasons for OFF indications Cone of Confusion Out of Range/Unreliable 90° from selected course
0
0
30
90
270
60
300
33
0
24
0
12
180 KING
0
21
0
OBS
16
Cone of Confusion
Zone of Ambiguity
"A" and "B" signal received Only "A" signal received
Only "B" signal received Neither "A" or "B" received
VOR station "A"
VOR station "B"
Fly from one point to the other keeping the CDI centered Bracket by keeping a stabilized crosswind correction
Draw out which way you need to turn to intercept Turn to heading and set OBS to desired radial Track inbound on new radial
Use two VORs to find your exact position Center both VORs with a from indication Draw out the radials
Where they cross is where you are at
Advantages
Limitations
Concise form of
Line of Sight
Navigation Easy to interpret position Not heading sensitive Provides multiple courses TO/FROM the station
Range
Advantages Not limited to Line of
Sight Simple form of Navigation
Limitations Errors ▪ ▪ ▪ ▪
Quadrantal error Night effect Terrain effect Precipitation static
Heading sensitive
Combination of several systems to provide pilot with the ability to land in conditions with poor visibility.
Localizer – indicates alignment w/ runway
Glideslope – indicates correct descent path
Outer Marker – Final Approach Fix
Middle Marker – Missed Approach Point
Needle indicates direction of runway. Centered Needle = Correct Alignment
Needle indicates above/below glidepath. Centered Needle = Correct Glidepath
Correct Glidepath Descent Cone
Runwa
OM – Denotes beginning of final approach segment (Final Approach Fix).
MM – Denotes Missed Approach Point (MAP) Usually placed at decision height on glidepath. “If you can’t see the runway yet, go around.”
Represented by indicator lights with accompanying aural tone in cockpit.
When glideslope is unavailable, pilots may still make a localizer-only approach.
VOR ADF ILS LOC GS Marker beacons
Radio altimeters DME GPS Transponders ELT
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
VOR’s operate between 108.0 to 117.9 MHz frequency band System includes
VOR ground station or transmitter VOR receiver in aircraft ▪ In light aircraft this is often combined with the comm radio
Aircraft display ▪ ▪ ▪ ▪
CDI course deviation indicator TO/FROM indicator OBS omni-bearing selector or course selector ON/OFF flag to determine field strength
Antenna
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
VOR station continually transmits an infinite number of radials. The VOR receiver in the aircraft receives the signal and operates the visual indicator. The pilot determines the bearings of VOR station with respect to the aircraft.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Operation The ADF receives NDB (non-directional beacon)
signals in the 19 to 535 kHz AM broadcast low band. The ADF display pointer (RMI or radio magnetic
indicator) will indicate the relative bearing to the selected AM band in that range.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Combination of several systems to provide pilot with the ability to land in conditions with poor visibility. Components LOC (localizer) ▪ Horizontal reference GS (glide slope) ▪ Vertical reference Marker beacon ▪ Distance from runway Radio altimeter ▪ Very accurate altitude measurement DME (distance measuring equipment) ▪ Very accurate distance measurement
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Combined with the VOR system Utilizes 1 of 40 ILS channels between 108.10 to 111.95 MHz. Operation
The ground transmitter is located at the far end of the
runway and provides a valid signal up to 18 NM The CDI (course deviation indicator) gives full fly left/right deviation of 700 feet at the runway threshold.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Utilizes 1 of 40 channels between 329.15 to 335.00 MHz. Operates on the same principles as the LOC.
The GS transmitter is located between 750 and 1250 ft.
from the approach end of the runway and is offset 250 to 650 ft. The indicator is either an ADI (attitude-director indicator) or HSI (horizontal-situation indicator). ▪ Both indicators combine other indications for ease of use.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Marker beacon receivers operate at 75 MHz and sense the audio signature of 3 types of beacons. Blue outer marker (5 miles from end of runway) ▪ Modulated with 400 Hz Amber middle marker (2/3 mile from end of runway) ▪ Modulated with 1300 Hz White inner marker (1500 feet from end of runway) ▪ Modulated with 3000 Hz
Operation As the aircraft flies over each maker the appropriate light will flash
and an audible sound may be heard.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
The radio altimeter provides better accuracy then the pressure sensitive altimeters. Operation
The transmitter sends out a VHF signal downward then
receives the reflected signal. The transmitter-receiver unit calculates the time needed for the signal to transmit and return to obtain AGL (above ground level) altitude. DH (decision height) used for instrument landings may be incorporated in this system.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Range is up to 199 NM at the high end of controlled airspace based on line of sight with accuracy of ½ mile or 3% of the distance. DME operates on frequencies from 962 to 1213 MHz. Operation
The aircraft transmitter sends out paired pulses at specific spacing. The ground station receives the pulses and then responds with paired
pulses at the same spacing but a different frequency. The aircraft receiver measures the time it takes to transmit and receive the signal which is transmitted into distance.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Utilizes a 24 hour satellite system that is accurate within 100 meters and is unaffected by weather. Has 3 independent segments
Space segment – satellites Control segment – ground based monitoring segment – aircraft
Database updating and antenna maintenance are the primary concerns to the GPS . Will be the most widely used system in the near future.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
An automatic receiver and transmitter that can receive a signal (be interrogated) from a ground station and send a reply back to the station. Used to identify aircraft on radar
Identification or squawk is 1200 for VFR flight Squawk assigned by ATC for IFR flight Used for emergency transmissions
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Three modes of operation Mode A ▪ Location only, non-altitude reporting Mode C ▪ Location and altitude reporting Mode S ▪ Can do Mode A and C and also responds to TCAS (traffic collision avoidance systems)
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Required on all aircraft to provide a signal on crash landings that will enable search aircraft or ground stations to locate the aircraft. Consists of a dual frequency radio transmitter and battery power supply with a whip antenna. Transmits on international distress signals of 121.5 (civil) and 243.0 (military) MHz. Activated by impacts of 5g or more or manually. Transmits up to 100 miles at receiver altitude of 10,000 ft for 50
continuous hours.
Located in an area of the aircraft where impact damage will be minimal. Tail cone area Aft top of cabin
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Three switch positions: AUTO, OFF and ON Testing may be done under the following conditions: Tune VHF COMM receiver to 121.5 MHz Only within the first 5 minutes of an hour Only three pulses should be activated Listen for an audible signal when switched to ON position
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
The battery pack must be changed in accordance with the date stamped on the unit. The battery pack must also be replaced or recharged when it has been in use for more than one cumulative hour, or when 50% of the useful life or charge has expired. Testing should be performed regularly. Inspections must be made every 12 calendar months. Regulations FAR Part 91.52 References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
System inspections Antenna inspections Static discharge inspections Operational checks or any additional inspections required by the manufacturer
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Inspect the condition and security of equipment including wiring bundles. Check for any indications of overheating in the equipment or wiring. Check for poor electrical bonding Requirements are specified by the manufacturer.
Cables should be kept as short as possible, except antenna cable
which have a specific length determined in installation. Proper bonding on the order of .003 ohms is important to the
performance of avionics equipment.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Check instruments and radios for secure attachment to the instrument . Check that all avionics are free of dust or contaminates. Equipment ventilation openings must not be obstructed. Check all plugs, connectors, switches, controls for operation and condition.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Check all instruments for placards as needed. Check all instrument lighting and annunciator lights for operation. Check circuit breaker for placards labeling each circuit breaker installed.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Check for: broken or missing antenna insulation lead through insulators Safety wires
Cracked antenna housing Missing or poor sealant at base of antenna
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Check for: Correct installation Signs of corrosion
Condition of paint/bonding and grounding Bonding of each antenna from mounting base
to the aircraft skin. ▪ Tolerance 1 ohm, maximum References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Check for: Physical security of mounting attachments, wear or abrasion of wicks, missing wicks, etc. Assurance that one inch of the inner braid of flexible vinyl cover wicks extends beyond the vinyl covering. Assurance that all dischargers are present and securely mounted to their base.
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Check for: Assurance that all bases are securely bonded to the skin of the aircraft. Any sign of excessive corrosion or deterioration of the discharger tip. Any lighting damage shown by pitting of the metal base. The ohm value of the static wick itself per manufacturer’s instructions. References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Transponder Per FAR 14 Part 91.411 and 91.413 ELT Per FAR Part 91.52 Functional checks of all other COMM and NAV systems per the manufacturer’s instructions
References: Aircraft Electricity and Electronics pg: 294-328, AC 43.13-1B Chapter 12 Section 2
Ground station oriented to magnetic north, transmitting directional information to aircraft Benefits
More accurate, precise flying Reliable Not susceptible to interference Voice Capable
Errors/Negatives
Costly to maintain Line-of-sight
Omnidirectional reference signal Directional signal from antenna rotating @ 1800 rpm Receiver uses phase discrimination Navigation in polar coordinates (rho-theta)
Distance Measuring Equipment (DME) & often Tacan are colocated with VOR
VHF – 108.0-117.95mhz Line of sight
1 LOP at a time 2 receivers give 2 LOPs (fix) VOR + DME = LOP & Arc (fix)
Not sensitive to aircraft heading Fly to or from a VOR or intercept a radial Radial – courses oriented FROM the station
High
1,000 – 14,500; 40NM 14,500 – 18,000; 100NM 18,000 – 45,000; 130NM 45,000 – 60,000; 100NM
Low
1,000 – 18,000; 40NM
Terminal
1,000 – 12,000; 25NM
* All altitudes AGL
360
Magnetic North
045
315
135º 270
090
135
225
180
VOR receiver gives 1 LOP called a Radial
Receiver Course Deviation Indicator (CDI) To/From ind.
Omni bearing selector
Initial Tracking Tune, Identify, Twist Turn OBS to center needle and figure out position (use FROM) Note heading on top of card ▪ If flying FROM station (radial), then turn to that heading ▪ If flying TO station, put reciprocal heading on top and center, then turn to that heading
Wind Correction Further away, more correction is needed to get back on track ▪ At 60NM from station, 1° = 1NM Generally, when within 20NM, 20-30° in direction of needle works Once needle centers, turn back towards original heading, but add wind correction of 5°
Station age CDI will become very sensitive, and then begin to oscillate Flag will switch from TO/OFF/FROM Switching Radials During station age, turn OBS to new course to fly
Intercepting If needle is alive, then turn towards it as if you were
tracking it If full deflection, first center needle to find what radial you are on Twist OBS back to desired course Parallel that course Turn 30-60 in direction of needle, depending on distance from station Once needle is alive, turn back in direction of desired course Follow tracking procedures
Radio signal sent out from aircraft to ground station. Ground station interprets this signal and sends back. Equipment in aircraft measures time and converts to nautical miles. Errors Diagonal (slant-line) distance from station to aircraft – not lateral ▪ Becomes greater the closer you get to the station ▪ Greatest when directly over station at high altitudes ▪ Limited number of queries
Uses ▪ Intersections/Fixes ▪ IAP ▪ Groundspeed
Pilotage Dead Reckoning Radio Navigation ADF
VOR/DME/RNAV
Electronic Navigation
Loran GPS Inertial
Celestial
Generic name for a system that permits point-topoint flight Onboard computer that computes a position, track, and groundspeed VOR/DME Loran GPS Inertial
Collection of antennas throughout the United States transmit signals Aircraft receiver calculates position based on intersection of multiple signals
GPS = Global Positioning System A space based, all-weather, jam resistant, continuous operation, worldwide radio navigation system. Provides extremely accurate 3D location data as well as velocity and time.
System of 24 satellites, 4/5 of which are in view at all times Receiver uses 4 of these to determine position of aircraft Each satellite transmits code, which contains satellite position and GPS time Receiver, knowing how fast signal was sent and at what time, calculates position
RAIM – Receiver Autonomous Integrity Monitoring Determines if satellites are providing correct data
WAAS – Wide Area Augmentation System Collection of ground receivers take satellite data and
correct it for atmospheric conditions Works based on known position of ground stations
LAAS – Local Area Augmentation System Same as WAAS, but on a smaller, more precise scale For terminal area around airport
Single range can lie anywhere on a sphere
Courtesy of Leica Geosystems
R1
Two ranges will intersect on a line, defined by the intersection of two spheres
Courtesy of Leica Geosystems
Three spheres intersect at a point Three ranges needed to resolve lat/long/altitude
Courtesy of Leica Geosystems
Civilian Uses Marine Navigation Air Navigation Surveying Search and Rescue Collision avoidance Agriculture
Military Uses Marine Navigation Air Navigation Rendezvous Close Air Mine Warfare Unmanned Aerial Vehicles (UAVs)
Dead-Reckoning Self-contained source of: Position, groundspeed, & heading Does not even need a receiver Cannot be jammed Gets better with use Applies a calibration correction after each flight
s(t ) a (t )dt
2
Acceleration is vectorially summed in x, y, & z. Output is compensated movement of the platform & for curvature & rotation of the earth.
Early systems required precise mechanical parts Bigger is more accurate
Modern systems can be: Mechanical (platform) Simple gyros Accurate
Electronic (strap-down) Few moving parts Smaller Cheaper
Aircraft systems use Pendulum accelerometers or MEMS ▪ Micro-electromechanical sensors Ring laser gyros ▪ To measure angular change INS complements GPS
Mechanical
Ring Laser Gyro
Pilotage Dead Reckoning Radio Navigation ADF VOR/DME/RNAV
Electronic Navigation
Loran GPS Inertial
Celestial
Advantages No power required Self contained Cannot be jammed Available everywhere
Disadvantages Dusk & dawn only Clear weather only Slow for aircraft Needs the art of nav. Navigator’s skill
Requires computation At least data entry
Circle of Equal Altitude DeRemer & McLean Global Navigation
Error increases with distance VOR/DME, ADF
Error increases with time DR, Inertial
Reliability Concerns GPS, Loran, Celestial
Human error
1. 2. 3.
Pilotage Dead Reckoning Radio Navigation ADF VOR/DME/RNAV
4. 5.
Celestial Electronic Navigation Loran GPS Inertial
Be suspicious. Check and recheck. If you cannot tell your engers your ETA at the destination, you are not navigating.
Assume you’re near your DR position Do not assume a huge wind just came up Use your VOR/DME or 2 VORs Look on the chart for landmarks Especially those that are shown small If you miss a checkpoint, hold your heading & look for the next one Do not guess where you are! If all else fails, CALL ATC (after all, YOU are paying for it)
Frequency Band: Airborne: 1025 MHz – 1150 MHz Ground :
63 MHz below Tx frequency 1025 – 1087 MHz 63 MHz above Tx frequency 1088 – 1150 MHz This gives 126 channels but two codings are used (X and Y) which doubles the capacity
As the name implies , DME provides information on the distance from the aircraft to the ground station Used to establish position along an airway and also to establish hold points
Frequency Band: Airborne: 1025 MHz – 1150 MHz Ground :
(L band) 63 MHz below Tx frequency 1025 – 1087 MHz 63 MHz above Tx frequency 1088 – 1150 MHz
This gives 126 channels but two codings are used (X and Y)
which doubles the capacity
General Principle: Airborne transceiver transmits a pair of pulses (spaced at 12μs for mode X and 30μs for mode Y)
Ground transmitter receives the pulses, waits 50μs and then
transmits another pair of pulses back to the aircraft Airborne transceiver measures the time between transmission and reception, subtracts the 50μs, multiplies by the speed of light and divides by 2.
This is very simple but gets more complicated when we want to service more than one aircraft We need a method of distinguishing among the signals from up to 100 aircraft. This is done essentially by generating a random set of pulses and correlating with the replies to determine the correct ones.
•Distance •Speed
•Time to Station Notes: 1. The last two are valid only if the aircraft is going directly towards or away from the ground station. 2. The DME measures SLANT RANGE to the station.
Altitude Ground Range
The ground station simply receives a pulse pair, inserts the 50 μs delay and retransmits it. To reduce the effects of reflections it will not reply to another interrogation for about 60 μs (dead time)
The ground station transmits 2700 pulse pairs per second regardless of the number of aircraft interrogating. The extra pulse pairs are called “squitter” If there are not enough interrogations to make up 2700 pulse pairs, the ground receiver increases its sensitivity until noise pulses trigger enough replies to make up the difference If there are too many interrogations, the receiver decreases its sensitivity so that the weakest interrogations get ignored
Using squitter has the following advantages: • The transmitter average output power is constant •The receiver AGC has a constant average signal to work with
•The ground receiver sensitivity is maintained at the optimum level •In the case of overload, the aircraft farthest from the station are dropped off first.
Using squitter has the following advantages:
• The transmitter average output power is constant •The receiver AGC has a constant average signal to work with •The ground receiver sensitivity is maintained at the optimum level
•In the case of overload, the aircraft farthest from the station are dropped off first.
Accuracy: The ICAO specification for DME is 0.5NM or 3% of distance Tests done on Canadian DMEs show that their errors are less than 30m. Integrity DME ground stations are equipped with monitors which can detect erroneous delays and out-of-tolerance power output levels. These shut the system down if and error is detected
Availability: As with most systems there is a standby transmitter which takes over when the main one fails. availability is well above 99.9%
Availability: As with most systems there is a standby transmitter which takes over when the main one fails. availability is well above 99.9%
ILS
Non-precision approaches supply the pilot with horizontal guidance only. (VOR, NDB, Localizer, Loc. B/C, GPS without VNAV) Precision approaches supply the pilot with horizontal and vertical guidance. (ILS, MLS, PAR, GPS with VNAV) ILS is the primary international precision approach system approved by ICAO and protected until 2010. ILS provides an aircraft with precision horizontal and vertical guidance to the runway.
Localizers operate in the VHF range and provide horizontal course guidance to runway centerline. Transmitters are located on the centerline at the opposite end of the runway from the approach threshold.
The signal transmitted consists of two fan shaped patterns that overlap at the centre. The overlap area provides the on-track signal.
The angular width of the beam is between 3°and 6°. Normally width is 5°, resulting in full scale deflection at 2.5°. The width of the beam is adjusted to be 700 feet wide at runway threshold.
The localizer may be offset from runway centerline by up to 3°. Localizers offset more than 3° will have an identifier beginning with X, aligned localizer identifiers begin with I.
A cautionary note will be published in the CAP whenever localizer is offset more than 3°.
Normal reliable coverage of localizers is 18nm within 10° of either side of course centerline and 10nm within 35°. Localizer installations provide back course information, and non-precision localizer back course approaches may be published. (ignore all glide path information on back course) Normally glide path will flag off. Caution: a localizer signal is transmitted differently than a VOR radial. Aircraft receivers are not supplied with azimuth information relative to magnetic or true north. It is simply a beam aligned with the runway centerline. For this reason CDIs will display normal sensing characteristics when flying in the same direction as front course alignment, but reverse sensing when traveling in the direction of back course alignment. (HSI will normal sense anytime front course direction is set on head of track bar.)
Glide path information is paired with the associated localizer frequency. The glide path is normally adjusted to an angle of 3° (may be adjusted 2° to 4.5°) and a beam width of 1.4°(0.7° for full scale deflection). The antenna array is located approx. 1000ft from the approach end of the runway and offset approx. 400ft. (if glide path is followed to the pavement touchdown point will be at the 1000ft markers) In installations with an ILS serving both ends of a runway the systems are interlocked so only one can operate at a time. Note: on a standard 3° glide path 320ft/1nm can be used to .
Typical final approach fixes are NDBs in Canada, but can also be identified by DME or VOR radial and DME as published. Fan Markers are commonly used in the US as a means of identifying aircraft location along a localizer. As the marker is reached a fan marker light will illuminate in the flight deck (if equipped).
CAT I: operation down to a minimum of 200ft DH and RVR2600 or ½ sm ground visibility when RVR not available.
CAT II: operation down to a minimum of 100ft DH and RVR 1200ft.
CAT III: minimums will be prescribed in the carrier’s operating specifications, carriers operations manual, or the CAP. (minimums are further broken down into A,B, or C with a CAT IIIC minimums being zero-zero).
Requirements: CAT II/III approaches require specific aircraft and airport capabilities. (ex: airport lighting, aircraft autoland)
Note: when CAT II/III approaches are being conducted the CAT II or CAT III hold line must be adhered to.
The following must be fully serviceable to meet CAT II/III standards: Airport lighting:
approach lights runway threshold lights touchdown zone lights centerline lights runway edge lights runway end lights all stop bars and lead-on lights essential taxiway lights
ILS components: localizer glide path
RVR equipment: CAT II- two transmissometers- approach end, mid-field
CAT III- three transmissometers- approach end, mid-field,
departure end
Power source: Airport emergency power as primary power source for all
essential system elements. Commercial power available within one second as a backup.
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