Radio Navigation Flashcards
Cycle
Interval between any 2 points measuring the completion of a single wave movement
Diffraction
Bending which occurs when a wave grazes the edge of a solid object through which it cannot pass
Attenuation
- Loss of wave as it travels through a medium
- Example is driving away from a radio station
Ionosphere
- Layer of rarified ionized gas believed to be caused by ultra-violet solar radiation
- Ranges from 60 to 200 miles above the earth and vary according to time of day, season, and latitude
Ground Waves
- Parts of the transmitted radiation that follows the surface of the earth
- Not subject to ionospheric interference or weather
- Suffers from surface attenuation proportional to the frequency
- Lower frequencies = less attenuation
Space Waves
Parts of the transmitted radiation that travel directly into space
Sky Waves
- Parts of the transmitted radiation that is reflected or refracted from the ionosphere
- Continues to reflect between the earth and sky until completely attenuated
- Skip Zone
- The distance between the end of the useful ground wave and the point where the sky wave is returned to earth
Ground Waves Radio Frequency Categories
- Very Low Frequency (VLF)
- Low Frequency (LF)
- Medium Frequency (MF)
Sky Waves Radio Frequency Categories
High Frequency (HF)
Space Waves Radio Frequency Categories
- Very High Frequency (VHF)
- Ultra High Frequency (UHF)
- Super High Frequency (SHF)
- Extremely High Frequency (EHF)
- Line of sigh transmission
- Signals not affected by time of day, season, precipitation, or atmospheric conditions
Characteristics of VHF Signals
- Do not follow the curvature of the earth
- Do not bend around obstructions
- Primarily space waves
- Reception is limited by line of sight
VHF Omnidirectional Range (VOR)
- Frequency Range is 108.1-117.95 MHz (VHF)
- 3 letter morse code identifier
- Transmits 2 signals, a reference phase and variable phase
- Beacon rotates at 6 RPM, green light flashes the instant the beacon passes magnetic north
- Actual VOR does this electronically
- Beams emitted by VOR called radials
VOR components - Omni Bearing Selector (OBS)
Selects Desired Radial
VOR components - Course Deviation Indicator (CDI)
- Shows aircraft position relative to selected radial
- Each dots equals 2 degrees up to a maximum of 10 degrees either side of radial
VOR components - Sense Indicator (TO/FROM)
Indicates whether the aircraft is the TO or FROM side of the VOR
VOR interpretation
- VOR interpretations are dependant only on the position relative to the selected radial
- Rule of thumb is that in order to properly navigate, the heading and the OBS must agree or else reverse sensing will occur
VOR Homing (Direct to VOR site)
- Tune to proper frequency
- Confirm proper morse code using IDENT
- Rotate OBS knob to obtain a TO indication
- Rotate the OBS until the CDI centers with a TO indication
- Fly the heading under the OBS indicator
- Adjust heading as needed to keep CDI centered
VOR Position Fixing (Finding exact location using 2 VOR’s)
- Tune and Identify VOR-A
- Centre the needle with a FROM indication, OBS is radial the aircraft is on
- Draw a line on map from centre of VOR compass rose out through the indicated radial
- Repeat for VOR-B
- Aircraft’s position is where lines intersect
VOR Serviceability Checks - VOR Test Facility (VOT)
- Sends out one radial, 360º
- CDI centres 360º FROM and 180º TO
- CDI must centre within 4º
VOR Serviceability Checks - VOR Check Point
CDI must centre within 4º
VOR Serviceability Checks - Dual VOR
- Same radial on two VOR’s
- CDI must agree within 4º
VOR Serviceability Checks - Airborne VOR Check
Over a known fix or landcmark CDI must agree within 6º
VOR Facilities
- Stand Alone VOR is radial information only
- VOR and co-located DME
- TACAN is similar to a VOR but uses UHF frequencies and is for military use, always has DME
- Often a TACAN is co-located with a VOR and is called a VORTAC
Automatic Direction Finder (ADF)
- Frequency Range between 190 and 415 kHz and 510-535 kHz (LF/MF)
- 1,2, or 3 letter Morse code identifier
- Transmits a single non-directional signal
- Mostly ground waves and some sky waves
- Follows curvature of the earth
- Reception is greater than VHF at low altitudes and over longer distances
ADF Principles of Operation
- Works similar to a portable AM radio
- A listener holding a radio turns themselves in a circle
- Strongest at 0º and 180º, nothing at 90º and 270º
- Receiver uses this to identify 2 places the signal could be coming from
- Internal electronics resolve the sense and determine the signals actual source in relation to the aircraft
- This drives the needle on instrument
How to Use The ADF
- Tune desired frequency from the map using ADF radio
- Listen to the ident to confirm the correct Morse code identifier
- Once identified, return the function switch to ADF position
ADF Interpretation
- On the fixed card, 0 represents the nose while 180 represents the tail
- Pointer shows the relative bearing TO the station
- Basic ADF consists of a fixed card and a bearing indicator needle
- Needle always points TO the station
- Magnetic Heading plus Relative Bearing equals Magnetic Bearing TO the station
ADF Position Fixing (Finding exact location using 2 NDB sites)
- Tune and identify NDB-X
- Read the relative bearing of the bearing needle
- Use the formula to find the bearing to the station
- Calculate the reciprocal bearing to obtain bearing from the station
- Draw a straight line from NDB-X on the calculated bearing from the station on a map
- Repeat for NDB Y
- Aircraft position is where lines intersect
ADF Serviceability Checks (Ground Check)
- Identify station and confirm correct relative bearing
- Change mode to ANT and confirm correct behaviour of bearing needle
- Change mode back to ADF and confirm bearing needle returns promptly to correct bearing
- During instrument checks while taxiing, the ADF needle should swing to track the station during turns
- Since there are no flags on the ADF, ident should be left on to confirm operation
ADF Errors - Night Effect
Radio waves reflected back by ionosphere can signal strength fluctuations, especially just before sunrise and just after sunset
ADF Errors - Mountain Effect
High Terrain reflects radio waves
ADF Errors - Static Interference
Precipitation causes static interference
ADF Errors - Bank Error
Errors based on how the antenna is installed
ADF Errors - Quadrantal Error
Angular error caused by metal in the vicinity of the antenna
ADF Errors - Coastal Effect
Ground wave bending due to shoreline
ADF Errors - Needle Oscillations
Noisy Identification
GPS Principles of Operation
- UHF frequency is 1575.42 MHz
- Each satellite sends a series of signals
- The receiver determines how long it took each signal to reach it
- Because the speed of radio waves is known, distance can be determined
- Receiver triangulates position, and can determine track and groundspeed
- Receiver needs 4 satellites to determine position
Distance Measuring Equipment (DME)
- Operates in UHF range
- 960-1024 MHz for transmissions
- 1025-1150 MHz for replies
- Radio signal paired with VHF frequency at TACANs, VORTACs
- Aircraft DME automatically functions for whichever VOR frequency is selected
DME Limitations
- Slant Range error
- Greatest at high altitude close to station
Radio Detection And Ranging (RADAR)
- Short pulses of super high frequency radio energy fired from rotating transmitter
- Strike aircraft and are reflected back to sender
Primary Radar
- Requires no equipment on board
- Simply plots reflected radar energy on a screen
- Used by ATC to monitor airport and terminal areas
Secondary Radar
- Requires a transponder on aircraft
- Includes sqwuak code and other information
Radio Magnetic Indicator (RMI)
- Electric navigation instrument that combines a magnetic compass with an ADF or VOR
- Card of the RMI acts as a gyro-stabilized compass, and shows the magnetic heading the aircraft is flying
Electronic Flight Instrument System (EFIS)
- Displays flight data electronically
- Normally consists of primary flight display (PFD), multi-function display (MFD), and engine indicating and crew alerting system (EICAS)
