VHF Omni Directional Range Flashcards
Standard service volumes
- works on line of site; reception may be affected by terrain or other obstacles
- the 3 classes of VORs are depicted on charts as AIM 1-1-8
1. High altitude (H)- 1,000 to 14,500 range 40 NM, 14,500 to 18,000 range 100 NM, 18,000 to 45,000 range 130 NM, 45,000 to 60,000 range 100NM
2. Low altitude (L)- 1,000 to 18,000 range 40 NM
3. Terminal (T)- 1,000 to 12,000 range 25 NM - note to determine VOR range below 1000’ refer to AIM 1-1-8 for service chart
VOR ground equipment; this is the transmitter that broadcasts a radio signal that can be used for navigation. This facility is a cone shaped building
Radial:
Is a magnetic bearing outbound from the VOR station. There is one radial for each degree on the compass
Signals:
The ground station sends out 2 VHF signals. The difference in these signals is measured to determine the exact radial you are on.
1. Reference phase - signal is the same in all directions
2. Variable phase- rotates at 1800 RPMS, sends out signal on each radial
VOR facilities
- VORDME- when paired, DME is automatically dialed up the pilot does not have to dial up separate frequency for DME
- VORTAC/TACAN- VOR co-located with TACAN. Non military pilots can get DME from this
- sometimes a test signal can be heard it has 4 morse code identifiers
VOR cock-pit display
- OBS (omni-bearing selector) the desired course is selected by turning the OBS knob until the course is aligned
- CDI (course deviation needle) the CDI shows angular deviation from your selected course
- to/from indicator- this indicator shows wether the selected course will take the aircraft TO or From the station
- to identify a VOR- select VOR frequency, push the V button, turn up the volume and listen to the morse code, it should match what you have on your chart
RMI (radio magnetic indicator)
- RMI needle always points to the station and indicates MB to the station
- MB= what heading we would fly to actually get to the station
- compass card moves
HSI (horizontal situation indicator)
- heading indicator superimposed with VOR and or ILS indicators
- indicates magnetic heading of the aircraft and position of the aircraft relative to the selected course
VOR navigation
Orientation your position relative to the VOR
- put the desired VOR in corner 1 as your waypoint
- no procedure needed to track to the VOR
- make sure you are in VLOC mode
1. Turn up the volume and identify the station signal (morse code)
2. Rotate the OBS to center the CDI needle with a from indication and read the course, this tells you which radial you are on. You can also center the CDI with a TO indication to determine your direct course to the VOR - put in appropriate communication frequency
VOR tracking and intercepting
- select VOR frequency
- identity the station
1. Morse code identifier/check for any flags
2. Sent out every 10 seconds, low pitch - select desired course with OBS
- track to or from the station
- select heading that allows a 30 degree intercept to or from the station
- wait for CDI to center
Display on aeronautical charts
- chart shows frequency, position and morse code identifier
- magnetic north arrowhead usually emanates from VOR
- compass rose marked every 30 degrees
- victor airways
Fixing position using 2 VORs
- ID position by crossing radials from two VORs in reception range
Cone of confusion: caused by lack of signal directly over the station
- display will be inaccurate- NAV flag can come down/CDI (full deflection)
- To/from flag flips
- fly compass heading when near the VOR (within .5 NM)
Reverse sensing
- due to pilot error needle can point the wrong way
- back course
- wrong heading under course index
- wrong heading on ILS (HSI)
VOR receiver checks (FAR/AIM 91.171)
- must be inspected within 30 days for VOR to be current
- must log SPED
Signature
Place
Error
Date
VODGA
V- VOT test facility only transmits radial 360 (360 from or 180 to) error +/- 4 degrees (listed in A/FD) not a real VOR can be anywhere on the airport
O- Operator check; select a VOR radial that lies along center line of an established victor airway- then select a land mark along that radial at least 20 NM away from the station and over-fly it. Error +/- 6 degrees
D- Dual check; checking 2 separate VOR receivers (they are tuned to the same VOR station) error within 4 degrees of each other
G- ground check; specific location on the airport. Error +/- 4 degrees (listed in the A/FD)
A- Airborne; fly to a specific altitude, radial, distance over a specific landmark. Error +/-6 degrees (listed in the A/FD)
NDB (non directional beacon)
The NDB is the simplest form of radio navigation. For the most part, these are just AM radio stations and a device in the air to pickup and locate those signals.
NDB
- NDB is the ground based transmitter
- transmits radio energy in all directions
- operates on medium frequencies (between 200 and 1750 KHz)
- NDB classes
1. Compass locator - 15 NM range
2. MH class- 25 NM range
3. H class- 50 NM range
4. HH class- 75 NM range
Problems which reduce NDB signal accuracy
CMINT
Coastal effect
- caused by the NDB signal bending slightly toward the coastline when crossing at an angle
- cross shore at mor than 30 degrees
Mountain effect:
- caused by reflections of the NDB signals from mountains
Interference:
- can come from other NDB transmitting on similar frequencies, or AM radio stations (causes needle to wander, sound clutter)
- can hear radio or morse code-needle inaccurate
Night effect:
- signals can be refracted by the ionosphere causing interference with normal NDB surface waves
- results in wandering signal
Thunderstorm effect:
- causes the needle to be deflected towards a nearby electrical storm away from the NDB
ADF (automatic direction finder)
- ADF is the name for the instrument in the aircraft
- 3 components of the ADF
1. The ADF receiver installed in the cockpit radio panel
2. The antenna system
loop antenna (think OBS):
-rotatable - narrows the possibility of what direction the NDB is located down to a possibility of 2 reciprocals
Sense antenna (think to/from flag) - determines which of the two possible directions is correct
3. The cockpit display (needle always points to the NDB
RBI (relative bearing indicator) - relative bearing is the angle between the aircrafts nose and the direction of the NDB
- fixed compass rose, 360 degrees
Rotatable card: - compass rose must be manually aligned with the aircrafts magnetic heading
- gives MB without math
RMI (radio magnetic indicator) - similar to HSI
- easiest to use
- MB shown automatically
Navigation
Station identification:
- each NDB transmits its own 3 letter morse code
- the signal must be continuously monitored because there is no off flag to indicate signal failure
Intercepting/tracking/navigation:
- tune, identify and check instruments. Keep IDENT tone audible
- track TO the NDB turn to the tip of the needle
- track FROM the NDB turn to the tail of the needle
Homing:
- flying without using a wind correction angle keeping the needle on the nose of the aircraft
- flight path is going to be curved
Tracking:
- use WCA
- most effective
RMI-DME arcs:
- keep needle 10 degrees ahead or behind left or right
- as needle gets to be 10 degrees behind your left or right, turn about 20 degrees and wait for 10 degrees behind again before turning
